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Mediterranean portolan charts: their origin in the mental maps of
medieval sailors, their function and their early development

(an extended essay)

by Tony Campbell


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Mounted on the web 26 January 2021

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Summary Conclusions


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ABSTRACT

For at least a century and a half attempts have been made to explain the origin of medieval portolan charts but no sustainable answer has been found. In the absence of solid documentary evidence, clues, deduction, analogy and intuition have had to be used instead. The revisionist conclusions that follow are the result of a lengthy analysis.

Portolan charts are characterised by unprecedented geometric precision and newly invented conventions, among which are an underlying mesh of direction lines, place-names restricted to the coast, empty seas, intentional generalisation of the coastline, and coded markings for navigational dangers. Furthermore, the very concept of a chart for marine navigation was itself new. The area covered by the oldest surviving marine chart, the Carte Pisane (c.1270), namely the Mediterranean, Black Sea and sections of the Atlantic coasts, would remain the norm for the next two centuries.

Before the appearance of the portolan chart an open-sea (pelagic) mariner, from any early period, would have needed a mental map of at least part of the Mediterranean, allied to the ability (prior to the invention of the magnetic needle) to determine direction, by means of a mental wind compass – for which there is indeed documentation. He would not have set out to sea otherwise. The mental maps would have been formed out of an expanding network of individual courses, memorised during a pilot’s life. Since many voyages would have involved ports around the sea’s periphery those, collectively, could have served to define the Mediterranean’s limits. Based on a collaborative pooling of those mental maps it would have been possible to ‘download’ the whole network as a single graphic design. Once the Mediterranean was visible as a whole, the conflicting estimates of a place’s position could be reconciled and omissions rectified.

Circumstantial evidence places the birth of the portolan chart in an unidentified west-coast Italian port, between 1154 and 1204. It was clearly designed by and for pelagic sailors and there is no evidence of institutional involvement or external financing. As an object of commerce, the charts had to be worth more to the sailor more than the cost of their hand-production. Since most of the charts’ users would have been illiterate, they carry no instructions for use, which had to be supplied orally instead.

No mathematical calculations or measurements were involved. In essence, the portolan chart was not a geographic or cartographic construct but a memorised experience transposed into a geometrically consistent graphic form, with the coastal outlines and toponymy added afterwards.


Table of Contents


For brief summaries see the Conclusions


 
INTRODUCTORY


The Road Map

The essay starts with a summary critique of previous explanations for the origin of the portolan chart. None had managed to provide a comprehensive answer or one that is historically plausible, which helps explain why none has proved generally persuasive. Rather than devoting much time to their limitations – although their arguments are challenged at the appropriate points – it seems more profitable to set out instead what it is hoped is a feasible alternative thesis. Inevitably, it must remain scientifically unproven and partly speculative, but it does incorporate what little hard evidence there is, and tries to match that with the (sketchy) understanding of early navigational practices, married to what is known of human needs and motivation.

A forceful argument will be made in support of the statement that there are no identified antecedents for the portolan charts. In particular, it is shown that Muhammad al-Idrīsī’s Charta Rogeriana of 1154 could have played no part in the origins story, whether as model or imitation [Powerpoint, Slide 1]. 1  Instead, the range of unique innovations seen in portolan charts (which, significantly, continue throughout the early period) makes it almost impossible that they could have had any predecessor.

The essay then states its central claim: that the charts must have derived, in some fashion, from the collective navigational memory of Mediterranean mariners. Open-sea sailing – as distinct from voyages that hugged an always-visible coastline – had as its first requirement that the pilot and helmsman knew where they were heading, before they left port. Proceeding without that knowledge would be more than foolhardy, verging on suicidal. That is at the heart of this thesis. The one-sentence foundation for this theory can be summarised thus: medieval pilots must have had a clear idea of the route to their destination, coupled with a reliable inbuilt mental wind compass that could envision the required bearing at all times.

Historians naturally seek out and value textual records. In this instance, the oldest surviving chart (the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118)) was certainly preceded by one pilot book (the Liber de existencia riveriarum et forma maris nostri Mediterranei – on which see a brief description in section E.1a), with a second (Lo compasso de navegare – for details of which see E.1b) being perhaps its approximate contemporary. The inter-relationship (if there is any) of those three unique, unsigned documents – none clearly datable – continues to be much discussed in the context of the ‘chicken and egg’ question of their respective priority. The charts’ supposed period of origin (now that the best estimate points to the late 12th century) is likely to have roughly coincided with the first appearance of a magnetic compass. Again, the historical record is unclear but an attempt is made to assess what significance (if any) the introduction of that navigational aid might have had for the genesis of the portolan chart. What would, however, have been of central importance was the wind compass held in a pilot’s memory. The discovery that the structure of this vital aid was neither described by contemporaries (apparently) nor had been analysed in any detail by previous historians, led to a lengthy digression co-authored with Roel Nicolai (see The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use, which has already been published separately).

The topics covered in this essay are listed in a separate hyperlinked MENU. Part 1 will delve into the charts’ prehistory to try to piece together the likely developmental stages that preceded the oldest survivor. 2  Spatial cognition, and mental maps in general, will be considered, along with medieval navigation and the charts’ possible (but here discounted) antecedents. Part 2 elaborates on the hypothetical ‘downloading’ of the mental map of the Mediterranean, while discussing, inter alia, the charts’ main features and purposes.

Recent (but pre-electronic) marine charts display almost all that a navigator needs, when used in conjunction with a pilot guide. The medieval chart, on the other hand, seems to have stood alone without secondary support. Or to be more exact, the essential elucidation must have come from sources little-discussed by historians, namely orally-transmitted instructions and the memorised experience of previous voyages. Orality and memory have a much larger place in portolan-chart history than literacy. Not only will it be argued here that the charts had no textual antecedent at all, but also that the portolani (Singular ‘portolano’ and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes, which had in the past been proposed as a possible source for the chart, must now be interpreted as depending on pelagic information from a marine chart for their very existence.

The essay is rounded off with a brief look at 16th-century surveys outside the Mediterranean, seeking any analogies that could have relevance for the prehistory of the portolan chart, followed by concluding remarks. An account of the essay’s methodology, summary conclusions and possibilities for future research are set out in separate webpages.

Constant reference is made to the following documents:


Table of Contents


For brief summaries see the Conclusions


 
Setting the scene

“Among the research problems connected with the portolan charts, the question of their origin is perhaps the most intractable”. 5   Published almost thirty-five years ago, that statement still applies. Winston Churchill’s description of Russia’s intentions in 1939 as “a riddle, wrapped in a mystery, inside an enigma; but perhaps there is a key”, matches the present difficulty. It is hoped that Churchill’s optimistic coda will now prove to be equally apt in this case. Was the origin of the portolan chart hiding in plain sight all along?

The assertion underlying this thesis, namely that a mental chart of the Mediterranean, paired with a relatively precise mental wind compass, must have been in existence, in some form, for millennia and that the portolan chart could be understood only as a collaborative downloading of that information, was considered outrageously revolutionary at its first airing in 2016. While it is yet to receive unqualified backing, resistance seems to be weakening.

But, at the risk of lessening the impact of this essay, it has to be pointed out that most of the argument’s individual propositions had already been asserted by previous historians, as evidenced by a number of the quotations in what follows. The novelty – because some of that can fairly be claimed – must lie in the fact that here, for the first time, those disparate claims and suggestions have been moulded into a single, and it is hoped, coherent theory.

For at least a century and a half, historians have struggled to reconcile the realistic outlines of portolan charts with their medieval context, since it was the first map covering a large area to be defined by its overall realism. The question usually asked was how that level of geometric precision could have been achieved with medieval instruments or mathematical expertise, and, above all, with the mind-set of the time? To suggest, as this essay does, the outlines of a possible solution may seem bold if not downright foolhardy. However, since nothing has plausibly replaced those earlier theories (now generally dismissed) which focused on a Classical or Islamic origin, or even a very ancient creation, the challenge needs to be faced. 6 

There is no certain ‘history’ of the portolan charts prior to the earliest survivor, the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , which, as was confirmed in 2016, and later by carbon testing, should be dated about 1270. For scans of the chart as it now is, and an 1852 facsimile made prior to the damage it suffered, see [Powerpoint, Slides 2 & 3, showing respectively the original and facsimile versions]. Prior to that is a prehistory almost as empty as the open sea, or with occasional half-seen features looming through the mist. Nobody recorded the charts’ birth. Neither the charts themselves nor any extant text throw direct light on their genesis or antecedents. Instead we have to rely on scattered written fragments: among those are passing references in later official records (usually emphasising their necessity at sea, without detailing how they were used), or comments about marketing matters, wills and legal disputes. 7  But nothing is said about their origin, purpose, on-board role, or the method used to reproduce the charts faithfully. If any pilgrim or crusader with an enquiring mind had sought information on those topics from a crew member, and then recorded it in their memorandum book, no trace of that has been found. The earliest landsmen’s descriptions of sailors consulting their charts date from the 15th century. 8 

This leaves the charts as crucial witnesses to their own history. Most of what is reliably known about them derives from close analytical study of the oldest survivors, and particularly their toponymy.

In the absence of archival sources to provide part of the answers, a possible hypothesis will be outlined, echoing what Ramon Pujades expressed in his monumental survey of 2007, namely that "a historical solution must be sought to what others have tended to treat as a purely geographical-cartographical problem". 9 

There are five interconnected questions needing to be addressed: when, where, by whom, how and why were the earliest portolan charts constructed? Cartometric analysis can certainly help with the technical component of the 'how' aspect, and explaining how the outlines made their way onto a map demands a joint historical and numerical answer, for which the results of cartometric analyses must be carefully considered. But the four other outstanding origin questions (when, where, by whom and why) are unlikely to be revealed through mathematics.

Instead, if there is any chance of determining where the portolan chart came from we must try to envisage the world out of which it emerged, the environment in which its creators and first users moved. The scant historical evidence must be sought out, both textual and cartographic, and when that runs out, we have to fall back on the constant verities of human nature and need, set into the specific context of medieval Mediterranean navigation. Ultimately, hypothesis, logic, common sense, intuition, analogy – none of which match the requirements usually demanded of historical evidence – will have to play an important role.

One aspect that must be squarely faced is the navigational capability of the medieval sailor. In a doctoral dissertation of 2014, Roel Nicolai concluded, at the end of a detailed cartometric investigation, that medieval mariners would not have had sufficient ability or equipment to have achieved the positional accuracy of the portolan charts: "The geodetic basis of the charts, expressed in their accuracy and their map projection, is far beyond the capabilities of the European Middle Ages". 10  That left him with the unanswered (and probably unanswerable) question: which era and place could have been responsible?

It appears to be the most likely scenario that Italian merchants acquired a body of ancient maps or charts through their trade with Constantinople ... The merit of the Italian mariner-traders would have been that they saw the potential of these maps, while the Byzantines, who preserved the heritage of antiquity but did nothing with it, may not have been greatly interested in them. It will have to be borne in mind that no person in the Middle Ages could have known how accurate these maps were. 11 

This essay calls for historical empathy, taking a more generous view of medieval aptitude and ingenuity, working on the assumption that people will always develop the skills they need for survival. It also argues that the experience of Mediterranean navigators would have been sufficient to supply the basis for the charts’ outlines, and that the generally accepted west coast of Italy should be retained as their place of origin, probably in the late 12th century. In other words, the central issue being proposed is not whether the early mariners had the geometrical ability to make a chart, but rather whether the level of their navigational skills, including direction-finding – which must have been commonplace among them for centuries – would have been sufficient for that purpose.

Prior to the emergence of the portolan chart, all navigational knowledge must have been memorised and shared orally. Hence the central task for any origins theory is to find a plausible way of explaining how the Mediterranean outlines made their way onto a chart in the first place. Significant research by Joaquim Alves Gaspar in 2019 has allowed us to reinterpret an important section of the oldest textual reference known, the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v). 12  Its statements of the distance and direction between paired places on the mainland coasts or islands, were previously considered to describe actual open-sea (pelagic) voyages. However, some were impossible, since they cross land, and that interpretation is no longer generally accepted. Instead – and this is the crucial point – it has become clear that the source for those statements was not direct sailed experience but rather measurements taken selectively from some kind of cartographic document. This confirmed that the portolan chart (or its antecedent) pre-dated the Liber, thus moving the focus away from a textual source towards an oral and graphic one.

Even more important, Gaspar was able to show that when the positions of all the paired termini at either end of those Liber statements were plotted out, a geometric diagram was created which defined the outlines of the entire Mediterranean with approximate accuracy. It is this (necessarily hypothetical) diagram – the result of what is here being termed ’inadvertent triangulation’An invented term for the hypothetical process by which pilots, before there was a marine chart, could have built up a mental network of the interrelationships between Mediterranean headlands, by means of observed directions and estimated distances. No mathematical calculations would have been involved – that, it is proposed, was the portolan chart’s source. So, the first question that has to be convincingly answered is this: what was the source of the pelagic information which would have been sufficient to build a wholly new cartographic image?

There are two other important linked questions that demand answers. First, given that their relatively small scale provided insufficient detail for the purposes of precise navigation, why were the charts conceived and created in the first place, and, second, why were they replicated for the use of paying customers for four centuries thereafter?

The ornamented charts that survive in disproportionate numbers from later periods were evidently not intended for use at sea. But if, as is still occasionally claimed, even unillustrated portolan charts served no navigational function either, then far more would have survived, instead of being worn out from overuse in inhospitable conditions. Furthermore, it is only once it is assumed the charts had a practical seafaring purpose that their peculiarities make sense.

While this essay is firmly focused on the charts’ hypothetical origins, it also seeks out evidence and meaning from the earliest documented periods, and especially from close examination of the oldest surviving charts themselves. Circumstantial evidence and the application of contextual logic offer a better chance of building up a picture, however tentative, of what the lost prototype chart might have looked like. There are some indications available, however, even if only by analogy. The Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) and its distant descendants as late as 1700 share a cartographic language made up of so many common features, as well as consistent purposes, that there a strong argument for tentatively extrapolating those backwards into the charts’ prehistory.

New logical deduction allows the date of the portolan chart’s inception to be narrowed to a brief window. As is explained in more detail below, 13 no marine chart could have been circulating before 1154, because the fifteen years al-Idrīsī spent gathering data for his vast world map of that year the (Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text) would certainly have included elements from a portolan chart if he had seen one. Based in Sicily, at the centre of the Mediterranean, it would have been impossible to avoid them. Conversely, working from the other direction, the new understanding that the Liber’s author was evidently using a marine chart for his pelagic measurements means that a functioning antecedent chart must have already been in place by the time that was written. The Liber’s sketchy details for the Black Sea (not taken from a chart) would fit in with a date after, but only shortly after, access was opened up to that in 1204. On the strength of those observations, the newly proposed date for the Liber is c.1210, and for the chart it was copying from, lacking the Black Sea, earlier than 1204.

In terms of the charts’ overall coverage, therefore, four phases can be distinguished: first, the core region, the Mediterranean, devised probably between 1154 and 1200; second, the eastwards extension to take in the Black Sea during the 13th century; third, the addition of the Atlantic coasts probably in the period 1300-1330; and then the steady recording of successive Portuguese exploratory voyages down the west coast of Africa in the 15th, leading to the voyages of discovery in the 16th.

There are intriguing parallels between the study of portolan chart origins and archaeology. What emerges from the soil might be the precise and complete outline of a building. Its purpose, say as a place of worship, might be broadly inferred from analogy with others elsewhere (if such existed). But who used it, what they believed, and what form their rituals took would probably remain elusive. In the Carte Pisane Accepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) we have the equivalent of that ancient building but little or no direct evidence as to how or why it was made. It did not come with a manual. With a leap of imagination, it might be possible to see the charts’ toponyms as akin to the archaeologists’ postholes, outlining a definite feature but requiring other evidence to establish their purpose – or in this case why those place-names were chosen.

The portolan chart is truly a cartographic masterpiece. The unprecedented step of setting down on parchment a precise maritime chart is comparable to replacing a quill-pen with a computer. The wide range of its cartographic conventions, almost none of which had been seen before, will be discussed individually. The word ‘invention’ seems appropriate, given that a number of the aspects of the chart’s cartographic language could, in a modern age, have been patented. It is easy to see cartographic innovations as unexceptional when they appear to be so sensible, and apparently timeless. But somebody had to have that ‘obvious’ idea, and then it had to be imitated. That the techniques introduced on portolan charts continued for so long is testimony to the clear and imaginative thinking of the unknown mariners who devised them.

They are the first maps of the Mediterranean and Black Sea that are fully recognisable to us, and what they offered seamen was unparalleled in its complexity and practical usefulness compared to anything made for landsmen. While merely a helpful guide for voyages that hugged the coast, the charts would speedily have become an indispensable aid for navigation when out at sea, where no land was in view to provide orientation. For an experienced pilot it would fill out the parts he did not already know, while a non-sailor would have gained access for the first time to the maps that mariners had always held in their heads.

Before starting to grapple with the origin question itself, we need to try and envisage the thinking and experience of medieval Mediterranean sailors prior to the portolan chart. It must first be understood that they were unlikely to have seen any cartographic image of their sea, and certainly not one that could have been of navigational relevance. Indeed, it can probably be assumed that mariners of the time had no clear concept of a drawn ‘map‘ of any kind. In devising a pragmatic working tool, the chart’s creators would have had to start from first principles. Their approach would have been free of ideology, imposed rules or precedent. What features were included and how they were treated depended on one thing only: how relevant they were for the charts’ purposes. That the cartographic conventions used on the oldest surviving chart cannot be found on any extant work from that time or earlier, is solid evidence that the portolan charts are sui generis. Their largest single innovation is undoubtedly an idea: the concept of the portolan chart, added to that the realisation that an animal skin, untrimmed, could be used to carry a map of the Mediterranean. In other words, what is special about the charts is their imaginative uniqueness. They were revolutionary not evolutionary. Paul Souriau’s verdict was that “Invention is not creation ‘out-of-the-blue’, but rather a combination of pre-existing ideas”. 14  There is little evidence of that in the case of the portolan charts even if they did emerge out of the deep blue sea.

Medieval navigators shared (broadly) the way they named places, how they described direction and how they measured distances – in ways that would be lost in later years and which we now struggle to replicate. Was it not logical that having already freely exchanged the details of pelagic courses and the mysteries of their wind compass they should pool their knowledge in a shared marine chart? After all, unlike other artisans, they were not in competition with one another; on the contrary, they were bonded by the common problems and threats they faced.

To put the achievements into context, the canvas under consideration concerns the world’s largest inland sea, the Mediterranean – with a width of 3,800 km and a north-south extent of 1,100 km, involving an overall coastline of some 22,000 km. To that should be added the 4,300 km coastal extent of the Black Sea, without considering those sections of the Atlantic coasts that were included on the standard chart.

This extended essay attempts to solve what may be the longest-lasting mystery in the history of cartography. 15  The conclusions it reaches run counter to existing theories that the charts’ source was text-based: whether some record of individual pelagic courses, or the littoral toponymic progression documented in the portolani(Singular ‘portolano’ and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes. Instead it will be argued, from the best indications available, that the origin should be identified in the joined-up network formed of the termini of those open-sea (pelagic) courses, which had been held from time immemorial in the memories of Mediterranean sailors.


Table of Contents


For brief summaries see the Conclusions


 
The contrasting milieus of sea and terra firma in the Middle Ages

There is an essential distinction that whereas the land divides (whether by language, culture, politics or topography) the sea unites. In medieval times, on terra firma, outside Latin-using circles, there was a babel of languages. Similarly, units of linear measurement had proliferated, even when they were notionally based on parts of the human body. Measurement would not come to be widely standardised until the metre was devised in Revolutionary France. At sea, on the other hand, such disparities were negated by a unifying environment made up of water (only very loosely divisible), the islands dropped into it, and the abutting coastlines.

In ‘Men of Sea. The making of an Identity’ one passage defines what sets sailors apart from others [note the timeless comment in the final sentence]:

The identity of the ancient sailors or men of sea according to our research is based on an open opposition to earth-based society and it is recognizable through the extremely dangerous conditions of their work and their isolation, their particular customs and their deep religiosity and superstitious attitudes, obviously encouraged because of the evident risks of their activities. These basic features were basically shared for every sailor from Antiquity onwards. 16 

Life at sea did not just benefit from co-operation it must have largely depended upon it. Leaving aside declared enemies, it would be surprising if those involved in maritime trade had not developed a tradition of mutual assistance. Even if there was commercial rivalry, that would have taken second place to the sharing of information about optimal routes, navigational dangers, the presence of pirates, any nearby ship afflicted with plague, local weather conditions, and so on. They were, after all, engaged in an endless struggle in the face of shared difficulties and risks. In that, contradictory sense, "If land is cosmos, ordered, the sea or the ocean is chaos, unordered". 17  Why would long-distance pilots have held back potentially life-saving information from those who might in time reciprocate? 18 

So, where social cohesion on terra firma had to contend with various fissiparous tendencies, the marine experience was very different. The Mediterranean was a shared sea and sailors were able to travel, in principle, to any part of it without hindrance. Its ports, along with the ships’ crews, housed a shifting population that was probably more heterogeneous than could be found anywhere else. Agreeing on a single unit to measure distance, sometimes across the featureless sea, must have been a precondition for the piloting of merchant vessels in the open sea. Hence the adoption of a ‘portolan mile’, even if those who used it seem not to have realised that there were regional differences in the way it was interpreted. 19  Seamen also needed to agree on consistency in the naming of places and natural features, as well as an understanding of the subdivisions in their shared wind compass. 20 

Besides those bedrocks of maritime lore there was a common cartographic language for the symbols on portolan charts that highlighted hazards and (admittedly, a slightly later development) the intentionally unrealistic shapes given to the islands in the Aegean and elsewhere as a mnemonic aid. When the location of the prime meridian at Greenwich was finally decided in 1884, replacing numerous nationally preferred alternatives, that was no more than an acknowledgement of the fact that most mariners were already using Greenwich, paralleling that same tendency towards maritime conformity that can be seen in the medieval period.


Table of Contents


For brief summaries see the Conclusions


 
Alternative origin hypotheses

It is remarkable that, during a period of at least 150 years, there has been no plausible explanation as to precisely how the information shown on the portolan charts was first gathered and subsequently processed. Roel Nicolai’s impressively thorough doctoral thesis was forced into a negative conclusion: “The geodetic and cartographic origin of portolan charts does not lie in medieval Europe”, but he was unable to offer an alternative birthplace. 21  The explanation, and there has to be a rational one, cannot depend on some unidentified earlier civilisation.

No contemporary text has described the data-gathering process that led to the creation of the portolan chart, indeed it seems highly improbable that such an account would ever have been written. Hence the only primary, albeit indirect, sources at our disposal are the earliest surviving charts (from the latter 13th century onwards), and two portolani (Singular ‘portolano’ and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes apparently from that same century.

The central question that has first to be decided is this:

Were the charts created out of a coastal survey, by stitching together regional surveys, or by joining up into a single system the open-sea (‘pelagic’) courses across the Mediterranean?

There seem to be four possible hypotheses:

(A) Joining up the statements in a portolano

Jonathan Lanman’s 1987 essay 22 purported to demonstrate that an overall chart could have been derived by plotting onto a map the stated directions and distances from one port to the next all the way round the Mediterranean (with its islands) and the Black Sea, as is described in Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396).

That must fail for one simple reason. While plausible outlines might be arrived at by those means for short stretches of coastline, the inevitable imprecision of both the stated distances (in miglia = miles) and the ‘wind compass’ directions would have made it impossible to build a total map of the Mediterranean in that way. 23 

Taking into account expected textual error and omissions in the sources used, this would have introduced steadily growing distortion into the broader picture. Such a method, carried out in sections, would never have reproduced the overall geometry of the Mediterranean in any usable form. There could have been no accurate matching of the north and south coasts, no reliable pairing of Spain’s features, for example with those of the Levant, and no understanding of the correct proportions of the Black Sea. As Joaquim Alves Gaspar concluded: “However recognizable in general terms the resultant outlines of the Mediterranean Sea, their accuracy and detail are hardly comparable with those of the charts they were intended to replicate”. 24 

(B) A coastal survey

The second hypothesis would be a putative coastal survey of both the entire littoral of the Mediterranean (as already mentioned, the world’s largest inland sea) and the Black Sea, including the former’s islands, presumably in a manner comparable in some way to those carried out elsewhere in later centuries.

This would be an elaboration of (A). Apart from repeating the problem of overall consistency, this can be readily dismissed on a number of other grounds. The most obvious is that it is unforgivably anachronistic to suggest that anybody in the 12th or 13th centuries would have contemplated sailing around the Mediterranean purely to create a general chart – of a kind never previously envisaged. Not only is there no precedent for any expedition tasked solely with producing an accurate survey of a coastline before, at the earliest, the 16th century, but it would have been well beyond the technical capabilities of the Middle Ages. Furthermore, it is impossible to envisage anybody conceiving, and paying, for such a venture. Indeed, later surveys were a side-product of voyages seeking to discover lands that might provide raw materials, trading opportunities or simply new territory. Since the coasts covered by the portolan chart must have already been adequately understood in general terms by sailors, the Mediterranean provided none of those incentives.

The scale of such an operation meant that it would probably have taken several years, and involved a ship with a dedicated crew. There would need to have been at least one attendant boat for close in-shore work as well – for instance in the Dalmatian islands and the Aegean – or for coasts that were bordered by shallows.

Finally, given its predictable inaccuracy, what would have been the purpose of such an exercise? How would it have been possible to identify and remove any errors inevitably produced by such a hypothetical coastal survey? The only logical way to achieve that would have been through the input of the combined pelagic courses (to be explained later). And why would developments have occurred in that sequence, given that the charts’ main purpose seems logically to have been to provide a tool for long-distance sailors, for whom an uncorrected coastal survey would have been of little or no use.

It is true that no one, to my knowledge, has directly suggested such a systematic coastal survey but it seems to be generally assumed (other than by Roel Nicolai and proponents of an Islamic origin), 25 that the portolan charts’ information is entirely medieval. It is just that nobody has been able to suggest how that might have been gathered and brought together in the form of a marine chart.

(C) The sub-charts theory

The contention that the portolan chart emerged from the joining up of a series of sub-charts of the basins and zones of the Mediterranean, which seems to be increasingly accepted, is discussed in detail later – and there critiqued in detail. 26 

(D) Mental maps

The fourth solution proposed for the enduring enigma of portolan chart origin is the source identified in this essay, namely the spatial memory of countless longer voyages that must have been held in the head of every widely-travelled sailor, and which, at some point, was set down in graphic form.

Of one thing we can be sure: whether the creation of the portolan charts came about by means of a coastal survey or by the drawing out of memorised courses, the work must have been carried out on board ship, and the methods must have been consistent with medieval shipboard practices and skills. Thus the focus on the charts’ creators must be paired with equal consideration for the ships involved [Powerpoint, Slide 4]. The charts represent a seaman’s view, and to hope to understand the process of creation we have to place ourselves mentally on the rolling deck of a ship.


Table of Contents


For brief summaries see the Conclusions


 

PART 1

THE ENVIRONMENT OUT OF WHICH THE PORTOLAN CHART MATERIALISED

 


A. ANTECEDENTS


 

A.1.  POSSIBLE CARTOGRAPHIC ANTECEDENTS FOR THE PORTOLAN CHARTS

Any search for plausible antecedents of the portolan chart needs to ask which of the cartographic models known to have been extant [though not necessarily accessible] at the end of the 12th century might have played a part. In what ways would different cartographic types, exemplified for example by the mappaemundi'World maps' in Latin (singular, mappamundi). Used to distinguish medieval maps of the world from those of Ptolemy and the portolan charts, the Peutinger Table, Matthew Paris’s itinerary maps, the Charta Rogeriana 27 or regional maps and diagrams, have helped provide any kind of realistic picture of the Mediterranean and Black seas? 28 [Powerpoint, Slides 1 & 5]. Furthermore, who, in 1200, would have needed, or been able to make use of, a realistic outline of the known world, with positional geometry as its primary concern?

Ptolemy’s astronomically determined co-ordinate geography might seem to be a suitable candidate (even assuming that it was available in Western Europe at that time via Islamic intermediaries, which is unlikely). The Geographia’s coordinates set out what was known in Alexandria in the second century CE and would not start to be updated until the Renaissance. In the period when the portolan chart seems to have emerged, cartographers had other priorities besides Euclidian accuracy. Indeed, despite the example of the portolan charts, with a few exceptions a regional cartography that used a measured scale and concentrated on the correct relative positioning of places – what might be termed ‘proto-scientific’ – is not seen for several centuries.

We should not have to rely on hypothetical antecedent maps, which are not only physically lost but also absent from the written record. If it is felt that such must have existed, how is it envisaged they were created and who would have drawn or used them? Those who support the claims of non-mariners as the charts’ progenitors need to identify who else, realistically, could have been involved. It is much more likely that the nascent portolan chart was ‘hidden in plain sight’ in mariners’ memories than that an invaluable Roman device was lost for 1000 years. Even if Greek mathematicians or Roman surveyors had turned their minds to the question of a marine chart, where would they have obtained the necessary information? Their periploi provide even less information than the medieval successors to those, the portolani (Singular ‘portolano’ and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes. Furthermore, the identical source question posed about the medieval charts would have to be asked in the case of a hypothetical Classical origin.

The iterative argument, which assumes that portolan charts must represent a continuation of one or more preceding cartographic genres, is not only contradicted by the lack of any such models but, even more compellingly, by the charts’ inclusion of a suite of unprecedented conventions, probably, in both number and originality, without parallel in the history of cartography. 29 

It cannot be said for certain that the portolan charts’ creator(s) had never seen a map of any kind. 30  However, we can be sure that whoever drew the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) was unaware of any map attempting to cover seriously those sections of the North Atlantic coasts which he casually included: whether Ptolemy, the descendants of a Roman model typified by the Anglo-Saxon (or Cotton) map, 31  or al-Idrīsī’s Charta RogerianaA 3.5 metre wall- map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text. 32 The most logical explanation for that new cartographic language lies in the portolan charts’ clear focus on navigation – to the extent that almost everything else is omitted – confirming that they were created, de novo, for the use of navigators.


Table of Contents


For brief summaries see the Conclusions


 
A.2.  WHY IS THERE A WIDESPREAD ASSUMPTION IN FAVOUR OF A TEXTUAL ORIGIN
FOR THE PORTOLAN CHART?

Assertion: Most sailors around 1200 were illiterate so why would a textual origin for the charts be likely?

Possibly because historians are used to dealing primarily with textual evidence, there seems to be a tendency – even perhaps an assumption – that, if the origin of portolan charts is ever discovered, it will take a written form, or at least have emerged from a literate group. Ramon Pujades articulated that viewpoint clearly, as in the following examples:

They were the products of the written culture of a specific period

The chronology of the advent and dissemination of nautical charts is totally inseparable from that of the rise of vernacular Romance languages to the category of vehicles of written expression

The information the [Liber’s] author had compiled to write his portolan and draw his mappamundi came from data on distances and directions amassed by a number of seamen-merchants-military men from the second half of the twelfth century who had recently learnt to read and write 33

Likewise, Patrick Gautier Dalché suggested that a pilot book which pre-dated the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) would have been at least a partial source for the charts. 34  The most likely textual source had at first appeared to be the Liber. However, recent re-interpretation of its pelagic statements 35 has concluded, first, that those do not describe actual open-sea courses and, second, that the information they contained could only have come to the Liber’s author from a lost cartographic drawing, from which he had extracted those measurements. Thus the earliest relevant surviving text proves not only to have played no part in the charts’ invention, but also to post-date what must have been some kind of graphic antecedent to the portolan chart.

Besides there being no surviving textual source, there are no references to missing works of that nature either. Even if a supposedly relevant text was identified it would do no more than prompt a further question: what, in turn, was its source? It would be like the rainbow, not the crock of gold at its foot. Furthermore, it is argued here that there is no logical reason to suppose that there would have been any textual stage at all in the charts’ origin and early development. 36  Instead, a diagram of open-sea courses based on sailors’ shared memories is posited as the underlying element, with coastlines and toponyms provided separately afterwards.

The portolan chart is a graphic document with a quasi-mathematical underpinning. No sign of a literary element has yet been identified in the charts’ DNA. That is surely no more than would be expected when the navigators’ milieu is taken into account. Sailors would probably have met, not in the study of a savant, let alone a monastic scriptorium, but on board a ship or in a quayside drinking establishment. Why is it logical to expect that a mental ‘map’ should have been downloaded into text before being re-envisioned in a graphic form which mirrored the original information? As the commentators on the 11th-century Islamic Book of Curiosities point out: “a transition from text to map is not as intuitive as it may seem to us today”. 37 

This chimaera of a missing urtext out of which the portolan chart emerged must be unmasked as an unfounded assumption (perhaps wish?) for the charts to have a documentary rather than mixed graphic and oral origin. 38  The textual-origin argument ignores the evidence that much of the crucial information on the portolan charts could have come only from memorised experience. Nor could the charts’ navigational detail (for example the coded dangers) have been reproduced adequately in a text.

Hence, not only is there no indication that a textual source ever existed, neither is there any likelihood of that having happened.

The comments above relate to the hypothetical textual antecedents for the portolan chart. For a discussion of text compared to orality and memory, in the context of the written portolani and navigational practice, see L.3. ‘Literacy or illiteracy’.


Table of Contents


For brief summaries see the Conclusions


 
A.3.  ISLAMIC ANTECEDENTS

A.3a. The Book of Curiosities

From an overview of early Islamic navigation, carried out by Yossef Rapoport and Emilie Savage-Smith, in connection with the 11th-century Book of Curiosities [Powerpoint, Slide 6], it has been established that there was plentiful, detailed information available to Arabic speakers and readers. 39  Indeed, the book’s “recording of navigation data in a systematic way is unique and distinctive”. 40  The portolan chart, despite its great originality, must defer in one overall respect to that Arabic manuscript, which has been justly described as the “first surviving example of a map looking at the coasts from the sea”. 41  However, realistic coastal outlines were intentionally excluded from the maps in The Book of Curiosities. What is notable is the mis-match between the text and the accompanying graphic representations, which were abstract and generalised. Indeed the work’s author explains that his marine maps were not intended to be “accurate representations”. 42 

It is valid to ask why the Islamic world did not invent the portolan chart, given that in the Mediterranean, “a shared and contested space, the problems facing Muslim and Christian navigators were the same. Much of the maritime nomenclature was common across the boundaries of faith, and the technologies that Christian and Muslim mariners used were broadly similar”. 43  Despite this, Rapoport and Savage-Smith rebut past claims to that effect: “In view of the evidence of the maritime maps of The Book of Curiosities, it seems highly unlikely that some early version of portolan maps was known in Fatimid Egypt. This is worth emphasizing because some have argued that portolan maps first emerged in the Islamic world”. 44 

That Italy rather than the eastern Mediterranean was the birthplace of the portolan chart might have been no more than accident. But it should not be assumed, from the overlapping navigational needs, that there were no major differences. One of the largest was the omission in The Book of Curiosities of references to hazards faced by shipping, yet that was certainly one of the main purposes of the portolan chart. Furthermore, the Islamic text’s concentration on bays, 45 which presumably shows a concern for ports with their mercantile relevance, contrasts with the portolan charts’ focus on the feature of the greatest concern for navigators, namely headlands. 46 

A.3b. al-Idrīsī’s Charta Rogeriana of 1154

The map under consideration was produced in 1154 or a little later, by Muhammad al-Idrīsī, for Roger II, king of Sicily. It has come down to us in the form of seventy separated sections, which, if they had been joined up, would have had the proportion of a 3.5 metre-wide wall map. That masterpiece needs to be clearly distinguished from a much-reproduced small circular world map, whose connection to al-Idrīsī is tenuous and whose importance has been overstated.

The large map, which is here referred to as the Charta Rogeriana, is dispersed through the pages of a manuscript volume, Nuzhat al-mushtāq [The book of pleasant journeys into faraway lands]. At issue is the question of whether the Charta incorporates any of the conventions otherwise specific to the portolan chart. If that was the case it would indicate that the latter was in existence prior to 1154. Alternatively, since the Charta is the only surviving map from the period before 1200 that could conceivably have provided inspiration for the portolan chart’s creators, is there any evidence that they had borrowed from the Charta? 47  In other words, which came first, and was either influenced by the other?

The attempt to answer that apparently simple question ran up against the problem that many of the details of the Charta’s creation and its later dissemination had to be teased out from conflicting and contradictory evidence. That analysis can be read in greater detail in a recently published web article. 48  The main conclusions that confirm the lack of mutual influence between the Charta and the portolan chart are set out in the following sections, which contrast the content and purpose of each.

A.3b.1. Comparison between the content of the Charta and the portolan charts

The Charta’s place-names are at their densest around the coasts – which would fit in with Roger’s desire to know about 'seas and gulfs' – but they appear to refer to settlements only, not to natural features, though a few rivers and mountain ranges are identified. However, despite the Charta’s deserved reputation for innovation and thoroughness, it would have been of limited use to a sailor. It is true that what is considered one of the signature features of the portolan charts, namely the placement of the toponyms inside the coastline, is also found on the Charta, but there is a significant difference. Whereas the portolan chart’s toponymy winds its way round the coastline in an unbroken sequence, with the names placed at right angles to that – which meant that the user had to rotate the chart to see them the right way up – the Charta’s toponyms are generally placed horizontally, to be read from a single viewpoint like normal text. Furthermore, the Charta’s patterned sea indicates there was no intention of depicting any offshore dangers, which was one of the portolan charts’ primary functions. Not even the feared Skerki Bank, to the west of Sicily – and hence not far from Palermo, where the Charta was drawn – was included. 49 

Interestingly, Sicily’s fairly regular shape was conveyed realistically, even if its size was massively enlarged. Although at first glance that would appear to flatter al-Idrīsī’s royal patron specifically, some of the other islands are also re-sized, whether magnified or reduced. For example, while Sicily is shown as about four times the size of Sardinia, that, in turn, is three-times larger than Corsica. This is another indication that geographical truth was not al-Idrīsī’s only consideration. By contrast, although the portolan charts might have simplified or distorted some features, that was never allowed to affect the overall geometric precision of the relative positions of the termini for pelagic voyages, since that underpinned the charts’ navigational function.

Roger and al-Idrīsī’s method of information-gathering, by interviewing multiple informants, would explain the unevenness in the quality of the map’s outlines. No amount of ‘improvement’ could have provided a single geodetic foundation comparable to the portolan charts’ self-correcting framework formed out of multiple pelagic courses.

There are a few similarities between the Charta and the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , for instance in the coasts around Tunis. 50  Nevertheless, it is difficult to see how al-Idrīsī’s own reported visits to the Maghrib could have had anything to do with those outlines. Moreover, the single most notable feature of the portolan charts – indeed their most distinctive coastal signature: the deep Gulf of Sirte – is only partially conveyed on the Charta where it is given a similar depth to that of two other, non-existent gulfs. Where the Charta is visibly more advanced than the Carte Pisane is in its portrayal of the Atlantic coasts, which lay outside the knowledge of that chart’s author.

A few instances of apparent agreement between the Charta and Carte Pisane might suggest borrowings from one or the other. But there are two separate arguments against that possibility: first, their respective purposes and, second, the Charta’s limited circulation.

A.3b.2. Different purposes of the Charta and the portolan charts

Both the Charta’s purpose and the way its information was gathered were fundamentally different to those of the portolan chart. Hierarchies of size and prominence had no place in the pelagically-fixed structure of the portolan chart, but al-Idrīsī was free to enlarge Sicily. The density of the inland detail confirms that al-Idrīsī and his patron were focused more on topography than hydrography, on geography rather than geodetic accuracy, and certainly not on the needs of pelagic sailors. In short, the Charta reflects primarily the outlook of a territorial ruler.

It is also instructive to compare the underlying cartographic structure of the Charta (with its apparent borrowings from Ptolemy) and the portolan chart. Each of the three was built up on a very different formal structure:

  1. The Ptolemaic image was formed explicitly from the astronomically calculated latitudes of hundreds of places, with their longitudes depending on reported distances. Relatively few of the place-names, around 13%, represent natural coastal features.51 
  2. The Charta’s unstated latitudes were derived from the seven equally spaced ‘climates’ of al-Khwārazmī.
  3. By contrast, the portolan charts, as is claimed here, were based on a diagram made up of the termini of interconnecting pelagic courses across the Mediterranean. These would have been downloaded from navigators’ pre-existing mental maps, with subsequent reconciliation of the inevitable variations in the placement of the termini. They were marine charts and hence concerned almost exclusively with precisely-positioned ports, islands and coastal features.

A.3b.3. Why the portolan charts were not used by al-Idrīsī

Roger II – or more realistically al-Idrīsī himself – spent fifteen years interviewing those who passed through the capital, Palermo, asking them about the geography of the world’s regions. A number of those informants must have been sailors. Had al-Idrīsī been shown a portolan chart, we can be confident that its user would have vouched for its accuracy and hence relevance for Roger’s project. Yet there are only fragmentary signs in the Charta of input from sailors and certainly no traces of the portolan charts’ many unique features.

It is always dangerous to argue from the absence of information but, in this case it seems justifiable because it is inconceivable that al-Idrīsī’s meticulous and well-documented, information-gathering exercise would not have revealed any nascent portolan chart that might then have existed. My failure to identify any traces of borrowings from a marine chart on the Charta, ties in with the majority opinion among researchers today. Tarek Kahlaoui, for example, concludes that "it is extremely difficult to argue for the Idrisian use of early portolan maps". 52 

The significance of this cartographic silence – which has not apparently been noted previously – provides robust support for a portolan chart origin date of no earlier than 1154 (when al-Idrīsī began his final version) and around 1158 when he completed it). 53 

A.3b.4. Why the portolan charts made no use of the Charta

The first and most obvious reason for this was the Charta’s inaccessibility. The 3.5-metre map was copied out in 70 sections, which were then distributed through an accompanying geographical text. The first time the full image is known to have been available was in a redrawing of 1928. Faced with the double impediments of a fragmented image and Arabic script, it is highly unlikely that anyone from outside the Islamic world would have seen the Charta or, if they had, would have been able to make sense of it – and certainly not at the time when the portolan chart was being developed. Hence, al-Idrīsī’s world map could not have served as any kind of inspiration for the portolan chart. 54 

The second argument focuses on the lack of idrisian aspects in the portolan charts. For the Mediterranean and Black seas little could have been learned from the Charta by the creators of the charts. But the Carte Pisane’s author could have benefited from seeing the Charta’s Atlantic outlines. These include the Bay of Biscay, entirely absent from the Carte Pisane, as well as England (thus named), Ireland and, however roughly, some understanding of the North Sea coasts.

Hence the Charta cannot be considered relevant to the portolan-chart origins question: if it had preceded the portolan chart, it clearly did not inform that, and if, conversely, the Charta followed the portolan chart, al-Idrīsī was evidently unaware of it.

This, in a similarly oblique way, offers further evidence against any Arabic contribution in general to the origin of the portolan chart. Likewise, the Charta could have had no influence on the information set out in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) , the oldest surviving portolano (c.1210). 55 


Table of Contents


For brief summaries see the Conclusions


 
B. SPATIAL COGNITION AND MENTAL MAPS

 


 

B.1.  EVIDENCE FOR THE USE OF MENTAL MAPS

Having reviewed the possible cartographic antecedents to the portolan charts and found none that could have plausibly served as their inspiration, an alternative source for their geometric content needs to be identified. The solution proposed here is one that would have been invisible at the time and that will have left no trace: mental maps.

Unless some textual validation emerges it will not be possible to prove this mental-map thesis. But we can readily cite analogies with other unaided navigation techniques – both those recorded historically and some observed in recent times – which demonstrate far more impressive feats than those that will be attributed here to medieval sailors.

The reverse question might be even more relevant: how could those navigating the Mediterranean before the compass not have had their own mental maps? “There has probably always been a mapping impulse in human consciousness”, as J.B. Harley wrote on the first page of the first volume of The History of Cartography, “and the mapping experience – involving the cognitive mapping of space – undoubtedly existed long before the physical artifacts we now call maps”. 56 

This investigation into the proposed mental-map source for the origin of the portolan charts considers a number of issues: human mental capacity (i.e., the brain functions relating to spatial memory), how mental maps work, and the use of mental maps for navigation (particularly by indigenous peoples). That will be followed by consideration of the skill-sets required when dealing with the specific circumstances found in the Mediterranean.

This section leans heavily on M.R. O’Connor’s, Wayfinding: the science and mystery of how humans navigate the world (2019) [Powerpoint, Slide 7]. 57  The author, an American journalist, ranges widely and deeply over the subject of human wayfinding. She shares her first-hand experiences in the company of Inuit hunters in the white landscape of the Canadian Arctic, Aborigines wayfinding in the Australian desert, and Oceanic mariners travelling vast distances guided only by the stars and waves. All of that is interwoven with a survey of the fast-moving developments in brain function research, focusing on the neurological basis of spatial orientation, and buttressed by interviews with the leading figures in the field. The science is not always easy but she takes us patiently through it. Though it is not directly concerned with Mediterranean navigation, this overview is a useful way into the theory and practice of human wayfinding.


Table of Contents


For brief summaries see the Conclusions


 
B.2. THE BRAIN AND SPATIAL MEMORY

B.2a. The workings of spatial orientation

Recent research into spatial orientation, as summarised by M.R. O’Connor, identifies two types:

The first is route knowledge, an ability to construct a sequence of points, landmarks, and perspectives that make up a path from one place to another. The traveller uses a string of memories of landmarks or viewpoints to recognize the correct sequence for getting from one place to another … The second strategy is called survey knowledge: the traveller organizes space into a stable, maplike framework, in which every point or landmark has a two-dimensional relationship to every other point ... Route knowledge relies on the traveler’s point of view and relationship to objects around them, what’s called egocentric perspective … Survey knowledge depends on what is called an allocentric perspective, a point of view that is objective, maplike … 58 

Clearly, pre-chart Mediterranean navigation would have routinely involved a combination of the ‘route’ and ‘survey’ strategies. Following a remembered or prescribed course formed out of visible waymarks, on the one hand, and navigating ‘blind’ in the open sea aided only by a mental map of the inter-relationships of places and features aided by a mental wind compass, on the other.

As Anita Devineni points out, the spatial map identified in the hippocampus may serve “primarily to encode memories: events are always associated with a particular place, so linking the place to the event may be a handy way of ‘indexing’ your memories”. 59  Such an aptitude would have had great relevance for memorising a long sea voyage with its occasional sightings of land. 60 

B.2b. Is spatial cognition innate in humans?

Could we be born with spatial memory recall? There are those who have suggested this might be the case. “While languages and navigational strategies may vary from one culture to another”, wrote John Edward Huth, “the wiring of the brain to create languages, mental maps, and other skills appears to be an intrinsic feature that we’re born with. Navigational skill depends on the interplay between memory, perceptions, and the mental map”. 61  David Lubinski thought that spatial ability “may be the largest unknown, untapped source of human potential”, while Alfred Ardila noted that “for thousands of years, human survival depended on the correct interpretation of spatial signals, memory of places, calculation of distances, and so forth, and the human brain must have become adapted precisely to handle this kind of spatial information”. 62 

Given the origins of human evolution, it would be unwise to rule out the possibility that we have spatial navigation skills that have some equivalence to those being identified via tests on animals. Edward Tolman’s celebrated 1948 article, ‘Cognitive maps in rats and men’, 63 has been followed by other studies looking for parallels. Many animal abilities far exceed our own, whether in measuring time or maintaining direction over perhaps thousands of kilometers, but it is now thought likely that all species have some kind of a bio-compass that can respond to the earth’s geomagnetic field, even if, despite half a century looking for it, the evidence has not yet been found. 64  As the Inuit historian, Ken MacRury, explained about hunters in the Canadian Arctic: “They wouldn’t get lost. And the dogs never got lost, never. Fifteen or twenty years ago, the old Inuit couldn’t believe when people started getting lost. They couldn’t believe it was possible.” 65

The place in the brain where the mental map has to be looked for is the hippocampus.

B.2c. The hippocampus

The flurry of recent research into this area of the brain continues apace and doubtless in ten or twenty years’ time there will be far more certainty about the function of that and other areas associated with navigation and memory, for example the caudate nucleus. It is clear that the hippocampus is critical for both cognitive mapping and episodic memory. It can objectively represent the environment in three-dimensional space and allows spatial relationships to be inferred (e.g. by taking a short-cut).

The hippocampus is very malleable. It includes “head-direction cells, which discharge in relation to which way our head is pointed on the horizontal plane, and grid cells, which fire as we roam an environment and build a coordinate system for navigating”. 66  Essentially, the brain links its map of where things happened to memories of what happened. The key to the growth of its grey matter is experience, not time, and it responds particularly to complex environments. Growth can effectively start as early as six years old, and it can be observed to expand in response to formal memory exercises. The central relevance of the hippocampus to the conjectured mental map of the medieval mariner is obvious.


Table of Contents


For brief summaries see the Conclusions


 
B.3.   TYPES OF MENTAL MAPS

B.3a. Definition of a ’Mental map’

What is a ‘mental map’? The definition given in Wikipedia is as follows: “A cognitive map is a spatial representation of the outside world that is kept within the mind, until an actual manifestation (usually, a drawing) of this perceived knowledge is generated, a mental map. Cognitive mapping is the implicit, mental mapping the explicit part of the same process”. 67  Jeremy Black makes a similar distinction between ”'unmanifested mental maps' (those that exist only in the mind), 'manifested mental maps' (such as sand paintings and Australian aboriginals carvings), and printed maps". 68 

On the other hand, in 1987 one meaning of ‘mental map or mental cartography’ had been defined in The History of Cartography, as “an image of the environment held in the mind to aid wayfinding or spatial orientation … [which] groups apparently carry in their heads as mnemonic devices”. 69  A possible current term might be ‘virtual map’ but, in the light of modern usage, that would be confusing and will be resisted here. Since this essay will discuss both the hypothetical content of sailors’ minds and its later manifestation in portolan charts, it would be unhelpfully pedantic to alternate Wikipedia’s distinction between ‘cognitive’ and ‘mental’ maps in those different contexts. ‘Mental map’ will therefore be used throughout.

B.3b. Western examples of mental navigation maps

Much could probably be learnt from the modern Vendée Globe, a single-handed, non-stop yacht race, in which participants sail around the world without the navigational aids taken for granted today. Earlier entrants were denied GPS and today they have to rely solely on sextants, paper maps and the stars; the magnetic compass is banned. A rather different example of traditional navigation is the story of the Hokule’a, a double-hulled Polynesian voyaging canoe, which covered nearly 50,000 nautical miles over a period of forty years, without the use of Western instruments, maps, or charts. 70 

We no longer have access to medieval mariners but might it be possible to mount a research project that scanned the activity and physical development in the brains of these oceanic navigators undergoing the Vendée Globe challenge? [Although the all-important memories of past routes in the medieval instance would not apply there.] As a parallel exercise, the brains of the chart-less indigenous mariners of today (discussed below) could be studied, with non-sailing members of their respective communities acting as a control.

B.3b.1. London’s Black Cab drivers

The most obvious example of mental maps in action, albeit in an urban not marine context, is that of London’s Black Cab drivers. In what appears to those not involved to be an amazing feat, they create and then use a constantly updated, personalised mental map of 25,000 street names, 320 standard routes and 20,000 places of public interest, covering in all 20,000 miles [32,000 kilometres]. This process is aptly known as ‘The Knowledge’. Today’s drivers had learnt from an atlas, but they do not use GPS or carry paper maps. Their three- or four-year training is carried out when they are adults (usually supporting themselves with a job at the same time).

That needs to be contrasted with a medieval sailor’s focused experience, probably starting as a boy (when memories are more readily assimilated) and then spread out thereafter over perhaps half a century. Despite the fact that the majority of potential Black Cab drivers fail to complete the training, there are still 20,000 who have managed to pass and remain active today, keeping up with the steady stream of temporary or permanent changes in the London streetscape. In the light of that, it would be hard to contend that gaining a general (and in some parts detailed) mental picture of the Mediterranean would have been beyond the capability of a medieval navigator. 71 

Initial research in 2000, and other studies since, have revealed that not only was the grey matter in the hippocampus of the cab drivers greater than that of London bus drivers (emphasising the importance of the cabbies’ decision-making) but that “the amount of time spent in the profession correlated with greater volume, proving the growth was accumulated”. This continued enlargement in brain function throughout the driver’s career reflects the fact that the stored information involved was both growing and changing. The memorisation process had involved transferring an existing street plan in its entirety into a mental construct. Conversely, the fact that people today increasingly rely on GPS to provide them with a precise location is apparently leading to a reduced volume in that same part of the brain. 72 

For a comparison between the oral issues relating to the Black Cabs and the portolan charts, and specifically the need to keep their knowledge current, see L.2a. ‘Two modern usage comparisons: London’s Black Cab Drivers’.

B.3c. Indigenous examples of mental navigation maps

The wayfinding skill and confidence of indigenous hunters who have adapted to their very different environments with varied navigation strategies, is at times extraordinary. Some of the Aboriginal ‘songlines’ – routes across the landscape linking features marking the tracks of the ‘creator-beings’ – are related to star positions. Where a Western astronomer might be able to name 100 stars, Aborigines, who had been steadily learning from childhood, can sometimes name thousands. When making long journeys across the Australian desert, the Aborigines were found to “possess some of the most precise orienting abilities known to man”. Their wayfinding skill involved “some kind of dynamic image or mental ‘map’, which was continually updated in terms of time, distance and bearing, and more radically realigned at each change of direction, so that the hunters remained at all times aware of the precise direction of their base and/objective” (reported by David Lewis). A person interviewed said he knew the directions “not by the sun but by the map inside my head”. One Aboriginal group in Queensland (and some other indigenous communities elsewhere in the world) do not have relative, subjective terms, such as left and right. Instead, they have sufficient confidence in their own spatial ability to use fixed, objective terms: North, East, etc. 73 

In Oceania, the piloting techniques used by various island populations in the vast spaces of the Pacific Ocean, are ably covered by Ben Finney in The History of Cartography (Volume 2, Book Three). 74  In his introduction, on ‘Mental Cartography’, Finney summarises their attainments:

The navigational practices of Oceanians present somewhat of a puzzle to the student of the history of cartography. Here were superb navigators who sailed their canoes from island to island, spending days or sometimes many weeks out of sight of land, and who found their way without consulting any instruments or charts at sea. Instead, they carried in their head images of the spread of islands over the ocean and envisioned in the mind's eye the bearings from one to the other in terms of a conceptual compass whose points were typically delineated according to the rising and setting of key stars and constellations or the directions from which named winds blow. Within this mental framework of islands and bearings, to guide their canoes to destinations lying over the horizon these navigators applied vital information obtained by watching with the naked eye the stars, ocean swellsThe regular movement of rolling waves that do not break, steady winds, island-influenced cloud formations, land-nesting birds, fishing out at sea, and other cues provided by nature. 75 

For the Caroline Islands, Finney quotes from Thomas Gladwin:

Everything that really matters in the whole process goes on in his head or through his senses. All he can actually see or feel is the travel of the canoe through the water, the direction of the wind, and the direction of the stars. Everything else depends upon a cognitive map, a map which is both literally geographical and also logical. 76 

To Finney, the skills of the pioneering navigators, “must have included some competence in orienting and holding a course by reference to the stars, ocean swells, and winds, in dead reckoning, in sensing islands before they could be seen directly, and in incorporating newly found islands into some kind of cognitive chart”. 77  To test those methods, “since 1976 voyages over 2000 miles of open sea have been achieved”. 78 

As another example, this time from the Canadian Arctic, Robert Rundstrom concluded that “the historical record and modern cartographic research both agree that most Inuit maps, extensively tested through a century of use by non-Inuit explorers and field scientists, were extraordinarily accurate renderings of the landscape as sensually perceived”. 79 

We need to be careful about over-stressing possible direct parallels between the experience of Mediterranean sailors and indigenous mariners. For example, the Cook Islanders used a 32-point wind compass, as does the portolan chart, though those are presumably unconnected. 80  But neither should we deny the comparable demands made on all those who navigate over open seas seeking islands or distant shores. There must surely be some similarities in the solutions found and the mental capacity involved. There is no justification for assuming that the brains of indigenous navigators (whose skills have been observed up to recent times) worked in radically different ways to those of medieval Mediterranean sailors. It is always unwise to underestimate the ingenuity of those from a distant period, or a different culture, who either did not, or could not, leave a written record of their navigational practices.

B.3d. When mental maps are essential

One consideration that certainly links medieval navigation and indigenous wayfinding is that of necessity. In both instances, livelihood, safety, even life itself, depended on skill, memory, concentration, and careful observation when voyaging. In today’s world, “Navigation devices make vast reserves of distributed knowledge available to us in an instant. But, crucially, they never require us to possess information in our own memory in the way that successful navigators have been required to do till now”. 81 

As one indigenous hunter put it: “Whereas most people like to go places, the Inuit people have to go places”. Another Inuit tracker, Taukie, gave an insight into the paired skills of memorisation and recall: “When we’re taking in details in our head, we try to look at the little stuff. When we travel past something we look behind us because it looks different from that angle. Every detail we are trying to put into our heads.” 82 

Not all memorisation is intentional. In the Wikipedia entry for ‘Memory’ (seen 7 March 2020) there is the following statement about “the unconscious learning or retrieval of information by way of procedural memory, or a priming phenomenon”. Priming is explained as “the process of subliminally arousing specific responses from memory and shows that not all memory is consciously activated, whereas procedural memory is the slow and gradual learning of skills that often occurs without conscious attention to learning”. The Inuit tracker and medieval pilot alike would no doubt have committed material to memory both consciously and, at other times, without being aware of it.


Table of Contents


For brief summaries see the Conclusions


 

C. NAVIGATIONAL PRACTICE

 


 

C.1.  NAVIGATION IN THE ANCIENT WORLD

As Barry Cunliffe pointed out, “It was 9000–5000 BC that saw the beginning of seafaring in Europe … The Phoenicians were the first of the Mediterranean States to enter the Atlantic in the 10th century BC and their main home port was Gadir on the Atlantic”. 83  Another source locates the appearance of professional mariners and established routes in the Bronze Age,

the time where both archaeological records and texts confirm the beginning of the maritime specialization, that is, the appearance of sailors as distinctive professionals ... We can ascertain the existence at the IIIrd mill. BC, and especially for the IInd mill. BC, of established commercial waterways as it’s evidenced through the Ulu Burun and Cape Gelidonya wrecks. 84 

Thus, for centuries, indeed millennia, besides proceeding along a coastline (cabotage), ships had set sail across the Mediterranean (pelagic voyages), often out of sight of land, without the aid of navigational instruments, except perhaps a log line. 85 

Empires inexorably rise and fall, and maritime trade can be disrupted. But that was too vital for the parties concerned for it not to be continued, even if by indirect means. Hence there is no reason to suppose that seafaring practices – say those found effective by Roman pilots – would not have continued, possibly with improvement, up to the Middle Ages. Hence it is relevant to take note of what is known or conjectured about navigation in the ancient world.

We are fortunate that, with the highly literate classical world of Greece and Rome, we start to encounter written accounts, which are disappointingly missing for the medieval period. In his doctoral dissertation Danny Lee Davis made a thorough study of textual sources from the classical period. “In ancient literature”, as he explains in that major revisionist thesis:

“the oft-repeated themes of storm, shipwreck and death at sea led to the popular assumption among scholars that seafarers developed habits to minimize their exposure to this hostile element—hugging the shore to avoid the open sea, putting in at night, sailing only in summer, and using ‘seafaring manuals’ to help guide their way. While several recent studies have made some strides in overturning this overly simplistic view by highlighting aspects of navigation in certain areas and in certain periods, the ‘standard model’ lingers in both scholarly and popular imagination … My research concludes that both coastal and open-sea sailing were matters of routine in the commercial sector, that commercial seafarers did indeed sail at night and employ the stars to deduce navigational information, that winter sailing was a widespread practice, and that crews employed navigational strategies to weather storms, usually successfully.” 86 

When writing about navigation in the later Middle Ages, Renard Gluzman confirmed Davis’s account, noting that “crossing open water was an integral part of any long-distance voyage … Venetian vessels sailed greater distances and much farther from the coast than had previously been thought”. 87 

Among Davis’s many interesting conclusions is the following. “It is highly unlikely that any Greek or Roman seafarer used one of these works [periploi, the forerunners of the portolani (Singular ‘portolano’ and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes] … for the purposes of navigating from place to place”. 88  Davis’s views were supported by Carmen Obied in her 2016 doctoral thesis: “Regarding ancient knowledge of navigation, extant evidence points towards a practical knowledge of seaborne travel and orientation which developed through ‘mental-maps’ based on experience and practice, and was likely predominantly transmitted orally”. 89  Much of the above is corroborated by Pascal Arnaud whose point of departure was “the assumption that implicit or tacit knowledge structures have been used in ancient times to form cognitive maps for orientation”. He elaborated that, commenting that Classical Greek geography “was based upon durations rather than distances, and upon an original perception of orientations and directions. Thanks to that knowledge, based upon the repetition of experience through generations and apprenticeship, they were able to sail the blue sea without maps or instruments”. 89a 

Instead of enquiring whether the Greeks and Romans had marine charts, we should rather ask, did they produce graphic versions of the charts they apparently held in their heads, to which the answer is that there is no evidence of that.


Table of Contents


For brief summaries see the Conclusions


 

C.2.   MEDITERRANEAN NAVIGATION

C.2a. Pre-knowledge of the route

If landmarks were not going to be available as a guide, in the period before the portolan chart, pilots had to know beforehand, fairly precisely, in which direction(s) to head and roughly how long it would take to reach their destination. Another obvious point, which might be overlooked, is that for land to be recognised it had to have been anticipated. When planning a voyage, the pilot would need to take account of intervening islands, note where the voyage might be broken, or water and supplies shipped, and in particular, anticipate the dangers that were likely to be encountered en route. Any lesser assumption is surely untenable. Unless they had followed memorised courses, no routine trading, pilgrimage or military voyages could have taken place. 90  Indeed, these ‘sea roads’ are well documented from surviving texts and wrecks (which were more likely to have been caused by weather conditions than poor seamanship). The following pair of assertions that underpins this essay is therefore proposed:

Assertions:
Nobody would have routinely left port without knowing the direction to take, any islands or dangers likely to be met with on the way, and the approximate distance and time involved to reach the planned destination

Nor, in the period before the portolan chart and the magnetic compass, would they have done so unless they were confident of being able to determine at least one direction when in the open sea

So, lacking the information a chart could have provided, the medieval sailor had to depend on his own experience or on the instructions he could obtain orally from others. This might have been his shipmates or those he met in port. By definition, no-one travelled more widely in the Mediterranean than its sailors. And nowhere was there more international mingling than in its ports, for instance those on Italy's west coast, by common consent the birthplace of the portolan chart.

The mental abilities required for medieval navigation would fall into those two types described earlier in the discussion on mental maps: respectively, route knowledge and landmark orientation. 90a Because of the risks involved in open-sea journeys, navigators needed to acquire a packed memory of courses run and dangers avoided, backed up by the visual appearance of the numerous headlands, bays, river estuaries, coastal and island outlines, etc., they had seen. William Bourne, in his Regiment of the Sea (1574), noted that a shipmaster should “be a good coaster, that is to say … knowe every place by the sight thereof”. 91 

Cunliffe wrote that:

For any sea or stretch of coast, the accumulated sea lore would have been vast. It was essential to the well-being of maritime communities that it was kept up to date and passed on from one generation to the next. In preliterate times this would have been done by word of mouth, possibly in the form of chants or songs, or at least in rhythms that allowed the instructing to be committed to memory. 92 

The record of each newly completed voyage would need to be memorised, to join those from previous courses run, since remembering those details would be crucial when any came to be repeated.

Danny Lee Davis makes a number of interesting observations on routes actually taken as compared to those theoretically described, a distinction not generally recognised by historians:

Sailing vessels rarely traveled in straight lines. Instead of fixed routes sailing masters chose to sail within seasonal corridors of movement in which conditions were most favorable for efficient forward movement. 93 

He also pointed out that “No route, no matter how short or how often made, was ever repeated precisely. At odds with this notion, however, are the ubiquitous maps of finely delineated sea routes we find in studies of ancient seafaring, trade and economics”. 94  In other words, the focus on simplistic, generalised descriptions of pelagic routes may be misleading. Though his remarks derive from a detailed examination of Classical navigation (well supplied with textual sources), his elaboration of the argument is worth repeating for its likely application to the largely undescribed medieval context.

Based on our source material, and taking into account the multitude of variables involved in each voyage even in optimal conditions, we should instead envision ancient sea ‘routes,’ whether short- or long-haul, as wide maritime corridors of general movement between one place and another. These corridors were defined by environment and meteorological factors, by technological responses to the demands of sea travel and by the ever-shifting realignments of trade trajectories throughout the seasons, years and centuries. The aggregate effect was of loose bundles of overlapping lines connecting coastal and island nodes, and not of straight, single paths overlaced multiple times. 95 

C.2b. The skill-set required for navigation

We cannot hope to understand how medieval sailors navigated with a chart without knowing how they had managed without one. In other words, what did portolan charts offer pilots that they didn’t already have?

Prior to the chart and the magnetic compass, medieval pilots would have needed to interpret the sensory information they were receiving so as to answer three basic questions: where are we, where do we want to go, and how will we best get there? Navigating with a wind compass 96 might have been equivalent to a blind commuter today finding their way to work by means of remembered features and sensual clues, not available to their sighted colleagues. The focus needs to be more on those aspects, undescribed and almost entirely lost, rather than the well-documented, tangible mechanical aids.

Davis offers a relevant parallel from the Classical world:

Historical sources reveal an occupation of low social status that nonetheless required a prodigious set of complex skills and a practical knowledge earned from numerous hard years spent at sea—seamanship, crew leadership, maritime geography, winds, currents, weather prognostication and nautical astronomy, among others. Together these skills and knowledge constituted the “steersman’s art,” ta kybernetika, or the ars gubernatoris. 97 

When establishing the approximate position at sea, the 12th-century mariner would have used ‘dead reckoning’: the ability by long experience to estimate the direction and distance covered, by relating the ship’s apparent speed through the water to the elapsed time, with the use of astronomical and other indications. He would have had no instruments, apart from a log line. It seems likely that the magnetic compass was developed after the time of the first portolan charts 97a and the hourglass or sand clock somewhat later still. 97b  To determine the ship’s position, the calculations of distance and direction (using such things as the angle of the swellThe regular movement of rolling waves that do not break) were augmented by astronomical aids, and particularly the known bearing of the expected wind (which had provided sailors with a theoretical compass for centuries before they first saw a magnetic needle).

When estimating the ship’s speed, allowance would be made for a following or adverse wind, the swell, any current there might be, and the effect of tacking. As far as direction was concerned the mariner had to select the desired heading, maintain it, and, if forced off course, regain it. For this, the toleta de marteloio, ‘a trigonometric reduction table to aid navigation by dead reckoning’, 98 would have been relevant but it is not clear how widely it was used to calculate the actual course sailed when tacking into the wind. The oldest known textual reference to it is from 1295, though that does not mean it could not have been in existence earlier. 99 

C.2c. Sea signs

When cloudy conditions obscured the sun or the stars, navigators would have had to rely on their own senses. Even if, when calculating distance and determining direction, they may not have had the equivalent of perfect pitch in music, it must surely have been the case that those senses would have been heightened first in training and then through constant use. Medieval pilots would have been attuned to their surroundings far more acutely than those of us in the developed world today, even experienced mariners. The sophisticated layers of personal and very detailed information, which must often have been retained in visual form, would also have included a wide variety of sea sign. The following would be a probable, if incomplete, list of those:

Approaching land: signs such as orographic clouds (created by the topography of an island that might still be out of vision); sightings of birds, fish or aquatic mammals; 100 driftwood, seaweed or floating vegetation.

Coastal profiles: fixing location in relation to the appearance of a coastline would have depended on reference to what must have been a large part of a navigator’s visual memory

Currents: the portolan charts could have introduced a symbol for areas with strong, regular currents, for example between some islands and the mainland, but they did not. So there is no warning on the charts, for example, about the strong tidal currents in the Strait of Messina dividing Italy from Sicily with its Charybdis whirlpool, nor the Gibraltar and Dardanelles straits. The implications of those would have to be learned but, once experienced, would surely not have been forgotten

Depths: checked by soundings with a lead line, perhaps revealing the bottom deposit which might help to identify the area; measured soundings were only introduced to charts in later centuries, but the charts’ hazard symbols served a related purpose by highlighting dangerous shallows

Prominent natural features: when “viewed against the sky would have been fixed on the mental map carried by all successful mariners” 101

‘Set and drift’: a combination of wind and current that could be pushing the ship off its course

Speed: perhaps estimated by leaning over the side and watching the bow wake, or by using a log line

Swell: wind-generated waves which can continue to reflect a wind even when it has not blown for days 102 

Water: colour, appearance, even smell 103 

Weather: knowing what weather to expect and being able to anticipate dangerous conditions

Winds: which winds (both seasonal and diurnal) to expect; the trim of the sails from which the direction of a constant wind could be read

Wind compass: the mental wind compass is described in great detail in a separate essay – The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use – and summarised earlier in this one. 103a  Prior to the introduction of the magnetic compass, the ability to ascertain directions at sea, by relating observed astronomical and other phenomena to a memorised compass, was a pre-condition for navigating in the open sea

Even with a compass and other instruments, those senses and perceptions would still have been essential for safe and effective navigation right up to the time that radar, echo sounding and satellite navigation introduced the first fundamental changes into navigation. 104 


Table of Contents


For brief summaries see the Conclusions


 

C.3.  THE MENTAL MAP IN THE MEDITERRANEAN CONTEXT

Assertion: Details of pelagic courses in the Mediterranean must have been held in sailors’ memories for millennia, hence a 12th-century sailor would have been using some kind of mental map, in the absence of any textual or graphical guide

Compared to other indigenous navigation – in the Pacific, Arctic, Australian interior, North Atlantic, etc. 105 – the Mediterranean has a number of advantages. In the first place, its encircling coastlines provides a spatial framework, as Danny Lee Davis pointed out in the Classical context:

The intricate coastal rim served as the focus of navigation conceptualizations from an early date, functioning as the primary frame of reference in the ancient geographical tradition and reaching its most pragmatic expression as early as the sixth century BC. in the subliterary genre known as the periplus, or coasting voyage. 106 

The Mediterranean provides numerous islands to serve as waymarks or break longer journeys, and a shoreline of some sort would nearly always appear after a few days sailing. 107 

In some areas, coasts would have been constantly visible. Examples are the northern part of the Sea of Sardinia (taking in the Franco-Italian coastline); the western half of North Africa; Sicily and southern Italy; the Adriatic; Greece, Crete and the Aegean; Cyprus and the southern coast of Asia Minor and the Levant. However, “for over perhaps one third of the Mediterranean Sea there is no sight of land even in optimal meteorological conditions”. 108  That would also apply to most navigation across the Black Sea.

However, in other very different marine environments, such as Oceania, and particularly the Marshall Islands, navigators had to rely on the distinctive pattern of the waves (‘wave piloting’) to deduce where the islands are. Might areas of the Mediterranean have had their own navigational ‘signatures’ to aid in locating the ship’s position?

The Mediterranean mariner’s mental map coupled with memorised pelagic experience should have enabled any land-sighting to be recognised and identified, and what might lie over the horizon to be anticipated. To achieve that, he would probably have needed to memorise only a proportion of the 2,000 place-names found on a typical portolan chart. More important would have been the storing in memory of a number of long courses, as well as many other shorter ones within sight of land: for instance, sections of coastline or links involving islands. It is highly unlikely that medieval pilots had an encyclopaedic knowledge or had sailed all over the Mediterranean, although much of their understanding would doubtless have been acquired orally rather than through direct experience. As Grazioso Benincasa An ex-ship captain, he left us a range of clearly-drawn charts and atlases (1461-82) and a written portolano (1435-45) states in the introduction to his portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes of the Adriatic, Aegean and Black Sea (1435–45): “I will make mention of ports and places … according to my memory … These ports and the appearance of land features are not drawn from a chart but have been found out and viewed with my own eyes”. 109  The mental map thesis takes those individual limitations into account, positing an origin formed out of shared, rectified knowledge.

To put in context the mental effort required to learn and retain the details of each course, it may be relevant to mention comparable feats of memory. The Quran has 77,000 words (which are memorised by millions of Muslims, thus allowing them to use the title Hafiz, for as long as they continue to remember it). The Bible has around 750,000 words (though that seems to be beyond all except autistic savants). As mentioned earlier, the London Black Cab drivers have to memorise 25,000 streets, and much more besides. 110  Some examples from indigenous communities that continue to hold to their old ways, have already been described. 111  Had the mental load for medieval mariners been equivalent to that of London’s Black Cab drivers, devout Muslims or indigenous navigators, which is unlikely, then we could expect their hippocampus to have expanded in a similar way.

A medieval sailor may also have had one unnoticed advantage. It is justifiable to consider if a lack of literacy might have freed up mental capacity for memorised experience in place of book learning, or, perhaps more plausibly, the corollary of that which sees developing literacy as demanding its own part of a finite space. It is possible that what is known as the ‘Homer Simpson Effect’, where new information pushes out old, may have relevance, not only for neuroscience but also the mental map posited in these pages. 112

In 2009, the French cognitive neuroscientist, Stanislas Dehaene, advanced what he admitted was a speculative argument:

Reading invades the neuronal circuits destined for another use and probably brings about the loss of some of the cognitive abilities that were handed down to us by evolution... Thus, reading acquisition possibly reduces the cortical space available for our other mental activities. The neuronal recycling hypothesis makes us wonder if our illiterate ancestors had visual skills that we have now lost.

He also noted how traditional hunter-gatherers ‘read’ the natural world, in ways where we today are illiterate. “It is possible that reading animal tracks is the cortical precursor for reading.” 113 

Subsequent research by a team led by Maria Wimber reinforced the Homer Simpson effect, finding that “remembering induces forgetting by actively suppressing the brain activity encoding similar, interfering memories. They believe this is an adaptive mechanism that increases the likelihood that we will successfully encode and remember only the most relevant information”. In other words, to be fully effective the mental storehouse of medieval pilots would need to have been both carefully edited and refreshed. 114 


Table of Contents


For brief summaries see the Conclusions


 

C.4.  WAS SAILORS’ KNOWLEDGE THE SOURCE FOR THE PORTOLAN CHART?

On their own, a sequence of coastal observations would never have produced a coherent chart of the Mediterranean, since there would have been no way to relate opposite coastlines to one another. Only voyages – across both the narrower seas and the longer stretches out of sight of land, and with carefully recorded direction and duration – could have bound the extremities together and linked them, both to one another and to the intervening islands. That process would have created a nexus of nodal points (usually headlands) to bind the trigonometry into a plausible whole. In commenting on orally-transmitted pelagic descriptions, Cunliffe explained that this was the “way networks of knowledge were constructed”. 115  Numerous adjustments, when for example landfall was not where it was expected, and the infilling of the intervening detail via coastal observation, must also have played their part. But the notion that anybody sailed their way around the Mediterranean in an attempt to create a general chart, or indeed that they might have even thought of doing so, must surely be excluded as a wholly anachronistic concept.

Most historians of the Classical world take for granted that sailors used mental maps, backed up with oral transmission. As Cunliffe observed, a sailor “had to carry in his mind a cognitive map in which to position himself at all times”. 116  There is no reason to suppose that those traditions would not have continued, uninterrupted, into the Middle Ages. On the contrary, what could have caused a total break in the orally transmitted component of navigation lore, given that the trade in which most seamen were involved would have continued without extended interruption? In what significant ways would sailors’ needs or abilities, and the physical environment itself, have changed over a thousand years? It is being argued here, based on the premise of mental maps, that, in one very real sense, the portolan charts’ gestation period should be measured not in centuries or decades but in millennia, in other words from the time that ships started to follow repeated open-sea routes for trading purposes, and the records of those pelagic voyages began to be memorised.

Underlying this essay are two assertions: first that whenever information has been vital, there would have been a strong incentive to commit it to memory, and, as a result, that an experienced medieval mariner would have had a workable mental map of the Mediterranean. And second, as an extension to that, whoever first imagined the idea of a portolan chart, and anyone using the prototypes, would have already been skilled in navigating without one.

It is inconvenient for historians but, by its nature, a mental map leaves no physical trace. Nevertheless, previous commentators have already given serious consideration to the part that mental maps might have played in the origin of the portolan chart, even if only partially and certainly not as the sole source. For instance, Roel Nicolai suggested that “It is not improbable that Lo compasso de Navegare ’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) also contains some distances that were estimated from experience, notably Peleio [pelagic courses]”. 117  Ramon Pujades also considered the possibility of a mental map, although he does include caveats:

Nonetheless, in order to produce a reliable chart using no data other than those of distance and directions and the visual memory of experienced seamen, first it would have been necessary to compile the information culled from a substantial number of crossings, because perfection in terms of representation could increase only as the number of points grew that could be located in respect to each other with relative precision, which in turn was directly related both to precise calculation of distance and finely-tuned determination of direction. 118 

As a general comment, Joaquim Alves Gaspar and Henrique Leitão observe that pre-Mercator nautical charts:

carry inside their internal geometry the imprint of the activities of pilots on board, that is, a ‘signature’ of their artisanal origin and of the techniques used to navigate ... nautical charts were deeply influenced by the practices of the artisans who used them, but, simultaneously, such influence was almost invisible to contemporary scholars and present-day historians. 119 

To counter the argument that the precision of the sailors’ knowledge of pelagic courses would have been insufficient for effective navigation, recent research offers a contrasting view. In his study of the pelagic courses described in the early 13th-century LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v), Gaspar notes that “13 out of 18 directions are exact when expressed in terms of a wind rose of sixteen points … Furthermore, the 13 null-error directions include most of the tracks of 200 miles or more, as well as the two longest routes of all, those from Alexandria to Patera (650 miles) and from portus Bocchi to Bugea (700 miles)”. 120 

The only plausible sources of that pelagic knowledge would have been the following:

  • information passed on orally by others, perhaps an older relative or mentor, the sailor’s shipmates, or those in the port with local knowledge, and/or
  • the sailor’s own experience, i.e. the narrative and visual recollection of past voyages, committed to and retrieved from memory.

From which it surely follows that:

  1. A pelagic navigator – whose memorised store of the details of routes, hazards, etc. could, and often would, be all that kept him from mishap, disaster, even death – must have understood the vital importance of that information
  2. From his earliest time at sea, any youth who aspired to navigational responsibility would have needed to become proficient at committing such details to memory and preserving them in a coherent fashion (with each experience being supplied with its own mental label) so it could be recalled at will
  3. The skill and focused concentration required to create and maintain such specialised memory banks, equivalent in modern terms to a combined database and video record, might well have led to neurological changes. 121 


Table of Contents


For brief summaries see the Conclusions


 

D. DIRECTION-FINDING

 


 

D.1.  ASTRONOMICAL WAYFINDING

It was the stars and the sun that provided sailors with more precise and reliable confirmation of the direction they were sailing – as long as the skies were clear, and, as far as the sun was concerned, at the important times of the day. Not that extracting the required information was straightforward. At sunrise and sunset, for example, the sun only identifies east and west precisely twice a year, at the equinoxes. At other times, increasing with both latitude and the passing months, the rising and setting of the sun will indicate noticeably different directions. As a result, the sun in the northern hemisphere will rise and set further towards the north-east and north-west as it heads to the June and December solstices. A further consideration is that the sun’s meridian passage occurs up to 15 minutes before or after noon, but that refinement would probably not have been noticed by a medieval mariner.

Once a single direction had been determined, all the others could be interpolated by reference to the sailor’s mental compass (see the following section). Time could also have played a part in the direction-finding by determining when the mid-points were reached between dawn and midday, and between midday and sunset.

The disadvantages in measuring direction at those four times of the day, or by the North Star at night, when on a boat that was perhaps rolling or tilting, should not be minimised. Taking into account also the likely imprecision of the solar sightings, and the brief period those remained relevant, it seems likely that observing the direction of the swellThe regular movement of rolling waves that do not break, which might remain constant for long periods, along with other sea signs, 121a might have sometimes proved more effective direction-finding aids.

At night, the main guide was the North Star (also known as Polaris or stella maris), found in the asterism of the Big Dipper (or Plough) within the constellation of Ursa Major. All mariners would have known how to extend an imaginary line upwards through the asterism’s front two stars, continuing that line for five times the distance between those in order to find the bright Polaris star. Even though it provided a bearing for approximately half the time only, unlike the compass it had the great advantage that it did not vary with position nor change noticeably over time. For those reasons, it must have remained the ‘gold standard’ for some years after the magnetic compass was introduced.

Leaving aside such astronomical assistance, there is plenty of evidence that medieval mariners were skilled at dead reckoningEstimating the direction and distance travelled by relating the ship’s apparent speed through the water to the elapsed time, so as to find the position at sea, with an ability to hold a constant mental course on the open sea. 122 


Table of Contents


For brief summaries see the Conclusions


 

D.2.  THE MENTAL WIND COMPASS

When discussing the origin of the portolan chart, the mental wind compass is inseparable from the mental map that is being proposed as the chart’s ultimate source. As Ramon Pujades pointed out: “The question of the wind network thus becomes a fundamental aspect as regards the issue of the origins of nautical charts”. 123  It has already been asserted that mariners would never have set out on pelagic voyages without knowing what lay beyond the horizon, but neither would they have done that unless they were confident that they could recognise at least one direction once they lost sight of land. Put simply, without a mental compass there could have been no pelagic sailing. From time immemorial, open-sea pilots would have found ways of dividing and subdividing the horizon into equal-sized arcs, whose width would have matched the precision of their direction-finding abilities.

Determining direction is arguably the most important single aspect of open-sea navigation. Distance and time can be important, and forewarning of offshore dangers could never be ignored. But knowing where you are and where you need to go are crucial. If you are, unknowingly, heading in the wrong direction, other considerations have little relevance.

Since the Classical period, there had been alternative systems made up of eight or twelve winds. By around 1200, or probably earlier, a schema had been developed with eight named winds at its core. Unfortunately, the sparse evidence available about that wind compass is both conflicting and incomplete, and past attempts to interpret it unconvincing. It seems that the workings of the system were never written down; at least no relevant text has been found [Powerpoint, Slides 8 & 15].

Some months spent analysing the 1,287 directional statements found in the mid-13th century Lo compasso de navegare’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396), in partnership with Roel Nicolai, produced a report, which has been published separately online. 124  Roel’s analysis of the terms used in Lo compasso provided, for the first time, the full complement of directional instructions. This revealed that there must have been 128 directions (some as precise as 2.8 degrees). The rigid uniformity in those statements demonstrates a sophisticated, well-established mental compass. This could only have been derived, orally, from mariners. However elaborate that system appears to us, it is difficult to dispute that it must have been used (to varying levels of precision) by pelagic sailors. Why, otherwise, would it have been devised?

What has not been found, though, is the certain sequence of those subdivisions, and Roel and I had to settle, amicably, on different interpretations. Nevertheless, we were able to conclude that in the medieval Mediterranean there was a level of direction-finding ability sufficient to make pelagic voyaging acceptably safe. Furthermore, such proficiency must have been widely spread among pilots, and not the preserve of a select few.


Table of Contents


For brief summaries see the Conclusions


 

D.3.  THE MAGNETIC COMPASS

Historians have long been divided over the question of whether the magnetic compass was involved in developing the portolan chart – possibly even being a precondition for that – or if, alternatively, it played little or no part in that process at all. In the light of recent research, it makes more sense to review the evidence rather than spend time exhuming old arguments. 125 

The status of the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) in the discussion about the introduction of the compass is far from straightforward. The discovery by Joaquim Alves Gaspar that the pelagic statements in that work appear to comprise both those that had been determined astronomically and those deriving from a magnetic reading is of considerable significance for the charts' origin. In his estimate, the majority of the 159 pelagic tracks in the Liber’s summary reflect traditional astronomical methods, whereas deviations in other bearing statements betray a bias (unrecognised of course at the time) that resulted from the use of a magnetic needle. 126 

This glimpse into the crucial transition in navigation represented by the introduction of magnetic readings alongside those obtained by traditional methods carries with it further implications. Gaspar has also confirmed that the distances (which form one half of those pelagic statements) could only have been derived from a cartographic document because they are no more than straight-line measurements that do not reflect how those courses might have been sailed in practice. 127 

If the Liber's text and the hypothetical graphic predecessor of the portolan chart appeared at approximately the same time, there would then have been a gap of perhaps seven decades before the appearance of the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) around 1270. Analysis has shown that by that time all the directions had been determined magnetically.

D.3a. The introduction of the magnetic needle and magnetic compass

The earliest known reference to the use of a magnetised needle in the Mediterranean was made by Alexander Neckam in his De utensilibus and De naturis rerum, both supposedly written about 1190 (though possibly somewhat later), perhaps close to the moment of the portolan charts’ inception. From its original form, as a magnetised needle floating in a bowl, this would develop into a dry-pivot compass pointer, which would have moved freely over a circular diagram, probably calibrated by means of abbreviations for the wind names. The added convenience of this more reliable compass, fixed on the fore-and-aft line of the ship close to the helmsman, seems to have been signalled by Petrus Peregrinus in 1269. 128  However, there are differing accounts of the sequence and dating of the respective developments.

In Julian Smith’s view, “No twelfth- or thirteenth-century author considers the magnetic compass a novelty. Most refer to its use on board ships in a matter-of-fact way, leading historians to suggest that the instrument was already commonplace in Europe by the mid-twelfth century.” 129  This observation on the magnetic compass implies that the transition from astronomical to magnetic navigation was widespread, speedy and straightforward. But was that definitely the case? There is a need to differentiate between the first appearance of the magnetic needle and the general adoption of that device, while at the same time distinguishing the separate introductions of the needle and, later, the compass card that was required for its effective use (on which see later in this section).

Other estimates of the compass’s introduction were more cautious, such as Roel Nicolai’s conclusion “that the mariner’s compass only came into widespread use in the course of the fourteenth century”. 130  That was supported by Ramon Pujades, who found no mention of the compass as a unit in notarial documents involving mariners before 1349, although that first instance could well refer to an instrument that had been in the possession of the sailor concerned for some time. 131 

Separate from, and for the present purpose, of greater relevance, is the issue of the way in which the compass needle was used. Neckam had written about sailors touching the lodestone with a needle, adding significantly, “when in cloudy weather … [or] in darkness”. 132  He had learnt about the magnetised needle in Paris and seems to have had no direct experience of its use. However, the much travelled Guyot de Provins – who visited Constantinople and Jerusalem, and may have been on one or more crusades – included a number of passages describing its use in similar terms, when he wrote for example, around 1204:

When gloomy darkness hides the sea
And one no star and moon can see
They turn on the needle the light,
Then from the straying they have no fright
For the needle points to the star. 133 

From those references it might be inferred that, in that initial period, the magnetic needle was used only when there was no alternative. However, in 1219 Jacques de Vitry, who had arrived in Acre as its bishop three years earlier, included in his ‘History of Jerusalem’ a description of the iron needle (acus ferrea) as being “very necessary for those that sail on the sea”. 134  That seems to be the first instance in which there is no stated qualification about the occasions on which it was used.

If in 1190 and 1204 the magnetised needle was regarded as a fall-back option, but by 1219 it was being referred to as an essential navigation aid, that suggests – albeit on that very limited evidence – that there was a step-change in the early 13th century in the way that the device was viewed and used. This is of considerable relevance for the origin debate, since that is also close to the period in which both the portolan chart’s progenitor and the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) , which evidently took its directions from a marine chart, are thought to have appeared.

It is natural to assume that the magnetic needle must have given more confidence to the process of direction-finding. Once someone had sailed with a compass, perhaps on an overcast day or at night, it might be wondered how readily they would have reverted to what could have seemed the cumbersome assessment of natural phenomena. But the early compass did have considerable drawbacks. In the first place there was more involved than just reading off the divisions on a circle (assuming it had one). During the first years, before the dry-pivot form was developed, the needle would have had to be retrieved from where it was stored, placed on a straw or sliver of wood, and floated on a bowl of water. Only then could the direction be read off.

That was just an inconvenience but there were larger difficulties. The astronomical markers sailors used are, broadly, unchanging. The North Magnetic Pole, on the other hand, will deviate in various ways from true north (the Geographic North Pole), depending on location (declination) and the passing of the years (variation).

It is therefore likely, in the early period, that the compass needle was a supplementary aid, rather than an entire replacement for the astronomical observations used for direction-fixing. This meant that mariners could, unknowingly, have been using two separate ‘norths’. The difference between those might often have been minimal but around the year 1200 the magnetic declination in the central Mediterranean was as much as 10 degrees east, with lower figures to either side of that: six for Portugal and four for the Levant 135  For generations, navigators had managed with the sun and stars, but now they were asked to transfer their trust to a device whose incomprehensible working must have seemed quasi-magical. 136   Unless it is contended that a discrepancy of up to 10 degrees would not have been noticeable within the limited accuracy some might assume could have been achieved at the time, 137 it needs to be accepted that medieval mariners would have been at least partially aware of the differing results from the alternative direction-finding methods, even if the reasons for those would not become clear until long afterwards.

It also has to be remembered that the addition of a circular card to provide visual recognition for some of the major directions seems to have been a significantly later invention. There are conflicting accounts of when the compass card first appeared, but the earliest mention seems to be the attribution of the invention to Flavio Gioja around 1300. Another reference is found in Francesco da Barberino’s, Documenti d’amore (1306–13), in which he described the lodestone and needle as indispensable, without specifically referring to the compass card. 138 

By contrast, Wallis and Robinson concluded that the first reliable reference was “by Francesco de Buti in 1380, and the first illustration in Gregorio Dati’s manuscript ‘La Sfera,’ c.1422”. 139  Even then the card is unlikely to have included much detail, perhaps no more than the quarter winds, as in a version of a 32-point system with no lettering in the c.1475 version of Dati’s ‘La sfera’ in the Library of Congress. It would be centuries before the compass card provided more than just a framework, to which the further subdivisions of a mental wind compass would need to have been mentally added.

D.3b. Adjusting from astronomical to magnetic bearings

For the compass proper to have gained a degree of trust equivalent to that of the earlier tried and tested mental methods, users would have needed first to recognise those discrepancies and then to compensate for them. It seems that that is indeed what they did, even if only selectively.

Discussion about the introduction of the compass has tacitly assumed that that development was not only a major benefit for navigators but a turning-point for the history of navigation, perhaps making the creation of the portolan chart possible in the first place. For navigation, it clearly had obvious advantages, for example in maintaining a constant direction (providing allowance was made for wind and current) or to confirm a bearing when it was possible to look back at a receding coastline. But the advantages should not be overstated. The compass could confirm the relative positions of features, provided they were intervisible. However, it alone would not have told the helmsman where he was when in the open sea, since that relied just as much on estimates of the distance travelled and the bearing previously followed, or the position of what was known to lie ahead over the horizon.

Nor should we necessarily start with the assumption that the infallible accuracy of the magnetic compass – putting to one side its initially unrecognised variation – would have swiftly replaced the direction-finding abilities of even the most experienced mariner. Unless the theoretical 2.8° precision seemingly revealed by Lo compasso’s’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) pelagic descriptions is interpreted differently 140  surely the pendulum has swung, at least partly, in the other direction, as an endorsement of the wind compass, and the relevance of the refined navigational skills required for its use. Set against the pole star (whose progression is sufficiently slow as to be undetectable during a sailor’s lifetime) and the predictable movements of the sun and other stars, combined with what the smallest of the wind direction divisions seem to tell us about the precision achievable by at least some of the pilots of the time, it can reasonably be asked: why would they have wanted to throw away that hard-gained mental and sensorial knowledge?

Thus, instead of altering the directions tied to the venerable mental wind compass, it seems that at some point in the 13th century a once-only decision was taken to swing the cartographic image 9 degrees clockwise, thereby re-aligning the entire chart in a single move. That is why an east-west line on the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) runs from Gibraltar almost precisely through Alexandria, whereas in reality Gibraltar shares its latitude with alexandretta (Iskenderun) about 500 km to the north, close to the point where the Levant coast turns to the west along Asia Minor.

Is there any other way such an alteration to the charts’ orientation could have plausibly occurred? Assuming – and this seems more than likely – that the earliest trial chart had already been laid down over radiating direction lines, the implementation of that change would have been simple. It is clear from surviving charts that the drafting of the compass lines [Powerpoint, Slides 8 & 15] and the hydrographic outlines was done independently from one another. It would therefore have been easy to rotate the coastlines against the north-pointing compass line if required. Once it was realised that the magnetic changes were continuous and unpredictable, and that a chart might last for a number of years, the chartmakers’ failure to track the changing position of magnetic north makes sense. If they had made adjustments, that would have led to unacceptable confusion because the user would be involved in a double calculation: first considering the ‘magnetic’ date of the chart and then having to calculate the intervening change. It would have been far easier simply to work on the understanding that, for the year they were currently in, they needed to make a particular correction to the chart’s unchanging orientation.

This one-size-fits-all re-alignment took no note of regional variation across the Mediterranean, even if mariners might have started to become aware of it by that time. However, once made, that change became permanently fixed on the charts. 141  Regional declination that resulted in different readings across the Mediterranean, as well as the progressive annual variations, were equally ignored. The close imitation enforced in the portolan chart replication process lies at the heart of their long history, and that conservativism provides a further explanation for the lack of any updating to the overall orientation.

However, we can perhaps learn, if indirectly, from the experience of later pilots. Even at the end of the 16th century, mariners were persisting with charts whose conformity with their compasses must have seemed erratic, sometimes increasingly so with the passing years. 142  It is fair to assume that they must have found a workaround. Perhaps they pragmatically rotated the compass card so as to keep it in alignment with the chart, or tested the accuracy of their needle against a sighting of Polaris.

Sticking with the 16th century, Henrique Leitão highlighted a different explanation. Even though pilots were aware of magnetic variation and declination, they did not usually correct for it. This was because the apparently erratic behaviour of the magnetic needle left pilots uncertain, and so they found it easier just to follow the uncorrected needle even though they knew that it would not point to true North. In addition, as he further points out, when a portolan chart based on uncorrected bearings was being used, it was logical to leave the compass equally uncorrected so as to match the chart. 143 

D.3c. Where does the magnetic compass fit into the origins debate?

The slender evidence available to us about the possibly interrelated, and perhaps contemporary, developments of the magnetic compass and portolan chart is insufficient to permit a confident account of the relationship between the two. The Carte Pisane’sAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) magnetic tilt tells us that a compensatory adjustment had occurred by then (c.1270), but no more than that. We do not know when and how the transition between astronomical and magnetic bearings was effected. Did those who drew the early versions of the portolan chart decide to make the switch, or, far less likely, did the conjectural urchart already show that magnetic bias?

Joaquim Alves Gaspar has identified the pelagic statements in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) as a mixture of directions obtained, respectively, by astronomical and magnetic methods. The latter could be distinguished because only those reflected declination. 144   Since it is clear that a graphic medium – the putative geometric pelagic diagram on which the charts were based – could not have accommodated directions obtained from two incompatible sources, Gaspar’s suggestion that “several sources were used in the compilation of his book”, seems likely. 145 

Even if the compass might not have been a pre-requisite for the chart, it could have played a major role in tightening up the geometry during the suggested ‘testing’ phase. If that is accepted, it could follow that the charts’ forerunner was based exclusively on astronomical observations, whereas by the time of the Carte Pisane the directions had become entirely magnetic, with variation treated, simply and incorrectly, as a single, uniform figure. However, the mixed message emerging from the discovery that the Liber’s list of pelagic courses includes examples of each type might imply that the transition was already under way at the beginning of the century.


Table of Contents


For brief summaries see the Conclusions


 

E. PELAGIC COURSES ACROSS THE MEDITERRANEAN

The existence of memorised open-sea routes in the brains of medieval Mediterranean sailors is fundamental to the argument being expounded here, namely that the downloading of those memories provides a large part of the answer to the long-disputed issue of portolan-chart origin. Roel Nicolai’s conclusion that pelagic observations formed part of the charts’ source material can be viewed as providing at least partial support for the mental-map theory set out in this essay. 146 

While much that follows in this section must, by definition, be speculative, there is a considerable amount of supporting evidence, which logically needs to be examined in some detail before considering any imagined prototype of the oldest surviving chart, the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . Attention will be directed in particular to the termini of the pelagic courses – i.e., the places where cargo was first shipped and where it was finally delivered. How might details about their location have been gathered?

It must first be understood that a statement in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) – for example, that to sail from Patera (in southern Asia Minor) to Alexandria (lines 762-4) involved a course of 650 milliara going due south – is not describing an actual pelagic course (even though the term per transfretum pelagi was used). What must be assumed instead is that the message it is conveying is no more than a straight-line distance, following a constant direction, between two pelagic termini. If that had been a real sailing voyage it would almost certainly have involved a number of changes of direction, because of the wind, intervening islands, etc. Furthermore, and particularly in that instance, it would often need to be different in the reverse direction.


Table of Contents


For brief summaries see the Conclusions


 

E.1.  13TH-CENTURY TEXTUAL SOURCES: THE LIBER AND LO COMPASSO

Two 13th-century manuscript texts survive, each in a single example. They are early survivors of a type of navigation guide known as a portolan or portolano (plural portolani). The later one, Lo compasso, clearly fits that description, the oldest, the Liber only partly so. These, and particularly the Liber, have already been referred to cursorily and they will recur regularly throughout the rest of this essay. So they need introductions.

E.1a. The Liber de existencia riveriarum et forma maris nostril mediterranei

The Liber de existencia riveriarum, preserved in the British Library, (Cotton MS Domitian A XIII, ff. 114r–129v) is arranged on two-column pages spread over 16 vellum folios measuring 19.6 x 14 cm. It contains a description of the Mediterranean and Black seas by means of a listing of consecutive localities with the distances between them. In addition, and of most concern for this essay, it also includes ‘pelagic’ (open-sea) tracks with the direction and distance between the terminal points.

This important work was rediscovered and studied in detail by Patrick Gautier Dalché and published with an extensive scholarly commentary in 1995 [Powerpoint, Slide 9]. 147 

[I make here a belated apology for having initially failed to appreciate the crucial importance of the Liber in this origins discussion and wish now to record my admiration for the breadth and depth of Professor Gautier Dalché’s scholarship. Modifications may need to be made to a few of his judgements in the light of fresh evidence but they will in no way diminish the fundamental importance of his Liber edition.]

Gautier Dalché had suggested a date of 1160–1200 for the Liber (p.9) but Ramon Pujades noted that the information about the Black Sea must post-date 1204, when it was opened up for trade. 147a  David Jacoby went further, noting that "there is good reason to believe that the compiler of the Pisan nautical guide upon which the Pisan compiler of the Liber relied obtained information on the Black Sea from Pisans operating in that region or involved in its trade after the Latin conquest of Constantinople in 1204." On that basis, he suggests that the Liber "should be ascribed to the first three decades of the thirteenth century”. 148  No compelling evidence has yet been identified in the toponymic data to help resolve this dating uncertainty. However, a recent examination of the Liber’s section about the Black Sea has proposed c.1210 for the compilation of that text. 149 

Noting that no earlier textual source has been identified, Joaquim Alves Gaspar used a new translation of the work’s ‘Prologue’ to show that “the author states clearly that he is about to describe the Mediterranean in writing and not, it is thereby understood, graphically. The likely reason for him to call attention to this detail is that the Mediterranean had already been described in a drawing.” 150  Gaspar goes on to state:

The author then gives his methodology; in order to represent those coasts on a cartula mappe mundi, he has prepared a little work (opusculum) containing the names of places with the distances between them, as well as the distances that separate Europe from Africa. For this, he has made use of data collected from mariners and travellers to supplement his own researches and studies, which had been conducted with the encouragement of a Pisan cleric critical of the way that the Mediterranean’s forma had been described in previous writings. 151 

Gaspar continues: “Although the main purpose of the work, as expressed in the prologue, had nothing to do with navigation, most of its information is of a navigational nature and reflects an origin connected to maritime matters”. 152 

Although the name of the Liber’s author is not known, he does leave us some clues to his identity. From his evident connections with Pisa Cathedral, and hence the likelihood that he was himself a cleric, it is not surprising to read, in the translation used by Gaspar, that he had “inserted the ancient [names] and their reason, according to the information of the books [the Bible], so that those who know the books may understand more easily”. 153  Building on that supposed identification, Pujades had suggested that “In all probability, the author of the Liber was one of the numerous clerics who acted as notaries and chaplains on the naval convoys ... Similarly, the first navigational chart makers would have belonged to this same socio-professional group”. 154 

The Liber’s author claims to have traversed the Mediterranean between Alexandria and Morocco 155 and certainly some of his descriptions must have been first-hand; however, neither he nor anybody else would have sailed systematically round the Mediterranean (and Black Sea) in order to put together such a handbook. Hence, he acknowledges the information provided to him, by “mariners and travellers”. 156  That mixture of experience and report is also reflected in the phrases he uses: “I have been able to know and discover”; “as I have seen and travelled”; “on the basis of calculation”; “that I could learn”. 157  Certainly more than just literacy was needed by the (apparently) first compiler of such a maritime guide. He must have had a methodical mind allied to a coherent plan for achieving a complete or at least broad coverage.

E.1b. Lo compasso de navegare

The second text in the spotlight, Lo compasso de navegare, is preserved in the Staatsbibliothek, Berlin (MS Hamilton 396), and is laid out on 107 vellum folios, measuring 21 x 14 cm. Considerably more detailed than the Liber, it likewise covers the Mediterranean and Black seas but has a full coverage of the latter compared to the Liber’s sparse toponymy. Lo compasso provides more precise bearings between neighbouring coastal localities than the Liber and includes many times as many ‘pelagic’ (open-sea) tracks.

The surviving manuscript has the stated date of 1296, but contradictory suggestions have been made: that the extant text may be both a revision of an earlier version around 1260 and at the same time a 14th-century copy, perhaps from as late as the 1320s. 158  The work’s first editor, Bacchisio Motzo (1947), had proposed that the surviving text of Lo compasso is an updated version of a work composed in the mid-13th century (probably before 1256 since it does not include Manfredonia, founded in that year); this is not disputed by its most recent editor, Alessandra Debanne (2011) [Powerpoint, Slide 10]. Pujades pointed out that its text refers to Palamos, founded by Peter II of Aragon in 1279, which would move forward the earliest possible date. 159  However, as Debanne notes, the description for Brindisi does not mention significant changes to its harbour that took place in 1276, which would imply a date prior to that. 160 

In a review article, Andrea Bocchi suggests that the stated date of the surviving manuscript should probably be read as January 1295 not 1296, which would have bearing on the noted absence of Villefranche, founded in 1295 on the site of Olivoli. 161  He also found evidence of scribal confusion that could indicate later interpolations. While these different indications warn against confident dating statements, it seems likely that the original version of Lo compasso was created at some point around the mid-13th century and that additions – although nobody has yet identified which those might be – were introduced up to and perhaps beyond 1295.


It needs to be emphasised that there is little similarity between the two portolani. That Lo compasso is not an imitation of the Liber is underscored by their itineraries proceeding in opposite directions. 162  The Liber’s author had ecclesiastical connections and, as he states, part of his motivation was to foster what might be termed biblical tourism. In contrast, Lo compasso should be considered as probably the oldest (and certainly the fullest) example of a true portolano: a descriptive itinerary around the Mediterranean’s periphery and between its islands. Navigation was central to the work’s concern and it appears have been aimed at mariners, providing basic information that would help them to navigate safely. To that end, it offers short evaluative and descriptive comments about entering a harbour, nearby navigational hazards, the appearance of the coastline, and so on. 163 

We owe our knowledge of these two unique manuscripts to the scholars who identified and interpreted them, without which there would be no textual material from before the likely date of the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . Those documents are crucial witnesses to the charts’ prehistory.


Table of Contents


For brief summaries see the Conclusions


 

E.2.   COULD THERE HAVE BEEN TEXTUAL ANTECEDENTS FOR THE PILOT BOOKS
AS OPPOSED TO MENTAL ONES?

We cannot rule out that the oldest survivor of the genre, the Liber, The ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) might have had antecedents (although its first-person narrative might argue against that). However, even if there are lost predecessors, the central question remains, where would their navigational information have come from: previous – even ancient – texts, or, as is argued here, sailors’ memories? Danny Lee Davis poses the same question about mental map or text in the Classical world, without being able to give a definitive answer:

From these observations and general conclusions are we to gather that seafarers completely shunned written aids and instead relied on their cognitive abilities alone to store and call up the important navigational information they learned from experience? Or did they use written materials that simply have not survived in any form. 164 

The improbability that such a precursor text ever existed can be best demonstrated by contrasting the likely content of such a hypothetical document with what was required for navigation. Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) was at least partly aimed at mariners, since it contains impressively detailed information for use by cabotage sailors. But what had appeared to be pelagic instructions for the open-sea transits have turned out to be no more than measurements from a chart. As Peregrine Horden and Nicholas Purcell emphasize, “the myriad possible combinations of port, shelter, detour and accident comprised by even short journeys could hardly be mapped or set in writing”. 165 

If instead we look in the other direction, at later portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes – in case archaic elements were resurrected there – we find a continuation over several centuries of what are primarily lists of distances and directions, mostly involving adjacent coastal points. Little extraneous information was added, apart from depth figures, such as those in Grazioso Benincasa An ex-ship captain, he left us a range of clearly-drawn charts and atlases (1461-82) and a written portolano (1435-45)’s portolano of 1435–45. 166 

At no stage did the pilot books introduce detailed sailing notes; even in the 16th century when printing would have made it easier to circulate information of that type. If 14th-, or more particularly 15th-century portolani, which survive in significant numbers, had included information that was clearly directed at mariners, there might have been some justification for claiming that those details could have existed prior to Lo compasso. But that was not the case. As for sailing directions as generally understood, these only appeared, in printed form, in fairly recent times and, rather than relying on written description alone, they supplied recognition views of coastal profiles.

That is not to deny that, in the Islamic world, written sailing directions, of some kind, do indeed pre-date the portolan chart. We learn, for example, from the 11th-century Book of CuriositiesAn Arabic manuscript of the 11th century including maps and descriptions of the Mediterranean, but not related to the portolan chart – see Section A.3a, and Rapoport & Savage-Smith, 2018 that its nautical information had been provided by “sailors, merchants and ships’ captains”. Furthermore, from a 10th-century Islamic source, al-Muqaddasi, it appears that, for the Indian Ocean at least, sailors followed instructions in unillustrated ledgers. 167  Tarek Kahlaoui describes how the text accompanying al-Idrīsī’s large world map provided a wide range of information from mariners, among which was “a list of sites, with the distances between them and their neighboring coastal sites”, along with “notes about the kind of goods (food and water) available at each location” as well as “tools to aid in the visualization of the outline of the coastline.” 168 

Hence, in the Islamic world at least, texts were certainly provided for use by mariners. But, crucially, this seems to have involved coastal sailing only, not the more challenging pelagic courses. Nor were those Arabic sailing directions imitated in the Christian West.

The authors of the ground-breaking study of The Book of Curiosities conclude, in words that have strong echoes for the primacy of the early portolan charts over text, that the author of that work “has unprecedented confidence in the ability of maps and diagrams to convey information. Unlike any other geographical treatise before this, the maps are stand-alone artifacts, unsupported by any accompanying text”. 169 

Furthermore, the very limited practical use of the written portolano for navigation 170 – confirmed by the lack of their presence alongside portolan charts in the inventories of sailors who died abroad 171 – makes it unlikely that most 13th-century sailors would even have been aware of their existence, let alone have used them, or probably been able to read them anyway. Not only can the use of pilot-books at sea be questioned, but there does not seem to be any trace of early logs of individual voyages written by mariners rather than passengers. That convention may perhaps have started with the voyages of discovery in the 15th or 16th century, becoming thereafter a routine requirement on long voyages, especially to the East.

There is no reason to suppose that medieval mariners would have had the equivalent of a trade manual, or indeed that any specialist craft at that time would have been supplied with written instructions. Nor was apprenticeship focused on book learning, since most artisanal skills were learnt through imitation and oral instruction alone. 172 

Three specific arguments against conjectural antecedents to the surviving portolani would be these:

  • What would such navigation notes have been written on? Paper was rare and expensive, and would not have fared well in the damp conditions at sea. They could have used vellum (as in the case of the Liber), but the high cost would also have increased the likelihood of its being recycled later, and hence surviving in book bindings in the way fragments of charts were preserved. That seems not to have happened
  • If such texts had existed, who would have done the copying and how would they have been paid for that work? What mechanism would there have been for circulating those nautical notes, since they would have existed in a milieu quite different from that of a monastic scriptorium or a scholar’s library? If there were few copies of those hypothetical texts, they would have had no impact; if they were widely distributed, we would surely have seen some examples (or references to them)
  • And what is the nature of the information such notes are likely to have contained? Perhaps instructions for avoiding reefs and shoals or tips on entering harbour (though a local pilot might have been used in those cases), but most of the relevant information would have depended on visual memory, and practical experience at sea would usually have involved responding to what was seen. 173 

We need to avoid the anachronism of trying to insert into the medieval period the content of much later navigational guides. 174 


Table of Contents


For brief summaries see the Conclusions


 

E.3.   THE TERMINI SELECTED FOR THE PELAGIC STATEMENTS IN THE TWO PORTOLANI

The pelagic courses tend to be interspersed throughout the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v), whereas in Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) they are either included in the general narrative or given their own ‘Peleio’ sections. Such courses usually, but not always, cover a considerable distance. Their essential characteristic is that they involve the ship setting out to sea, rather than just following the coast. In some instances, the journeys would be short enough to involve land that was always in sight, such as an offshore island. The network of courses mentioned in the Liber have been drawn out in the form of a diagram by the work’s editor, placed at the end of the volume. A necessarily more elaborate equivalent has been provided by Roel Nicolai for the far more extensive network described in Lo compasso . 175 

The pelagic statements are presented in forms like these:

'Liber': a Maluascia ad caput Malee Sancti Angeli inter eurum et austrum ml. .xx [From Monemvasia to cape Malée following a direction between south-east and south, 20 miles]

'Lo compasso': Acque morte all’isola de San Piero CCCCLXXXX millara per sirocco ver lo meczo di poco [Aigues-Mortes to Isle S. Piero, 490 miles following a direction between south-east and a little towards south] 176 

Unsurprisingly, the pelagic termini mentioned in those two early portolani include headlands, islands, commercially prominent ports, and occasionally mountains close to shore. 177  Promontories feature strongly among the termini. They were broadly of two types. First, those projecting out from the coast and therefore useful for marking the progress of a voyage. Second, a cape (whether on the mainland or protruding from an island) that indicated a change in the direction of the coast. A helmsman would have aimed for one of those after it had been sighted and recognised. He would then use it to re-align his bearing for the next stage of the voyage. Some of those capes and islands represented crucial turning-points. Good instances are Cape St Vincent which marks the point where ships turn towards the east for the entrance to the Mediterranean, and those that mark out the broad overall shape of Italy’s foot, Spartivento and Santa Maria di Leuca. As is argued below 178 they could also have provided the key locations used to construct a tightly interlinked network of direction lines and nodal points to form the geometric outline of a portolan chart.

Islands, both large and small, played a major role in Mediterranean navigation. Whether or not they were visited, they could serve as intermediate destinations. As might be expected, many of the islands’ outer promontories are named in the list of pelagic courses. 179 


Table of Contents


For brief summaries see the Conclusions


 
E.4.   THE PELAGIC STATEMENTS LISTED IN THE LIBER

Besides the main body of the Liber, which comprises a coastal itinerary linking one port or feature to the next, there are three additional summary lists:

  1. 159 adjacent places around the Mediterranean are paired in the ‘Prologue’, though the Black Sea is not included. These extended hops along the coast, akin to express stops on the New York subway, are additional to the detailed itinerary for which only distances are provided. 180 
  2. The ‘Prologue’ also includes a list of 22 longer-distance (transfretusLong-distance, or pelagic, courses usually out of sight of land) routes, where both the mileage and the direction involved are given. These are all repeated in the body of the text. 181 
  3. The text itself describes 196 transfretus routes, ranging across the Mediterranean, again with both distance and direction stated. 182 

Patrick Gautier Dalché supplied a pair of maps to reproduce the so-called ‘pelagic’ (transfretus) statements in the Liber (but see later for their reinterpretation as straight lines). 183  Recently, Joaquim Alves Gaspar has produced a single pelagic diagram, with additional tracks 184 [Powerpoint, Slide 11].

In his Appendix 3 Gautier Dalché provides a side-by-side comparison between the transfretus pelagi statements in the text of the Liber and their equivalents in Lo compasso, where they are referred to as peleio or pileggio. 185  However, few of the Liber’s pelagic courses could be linked by Gautier Dalché to those in Lo compasso (despite the latter describing about six times as many, 1,287) 186 and several of those matches involved a different nearby terminus at one end. This lack of overlap in the paired termini selected for the respective portolani demonstrates the absence of a standardised list of such pairings in the 13th century. Instead the authors of the two works presumably made their own selections of linked termini. In general, the independence of their sources was already evident from major differences in their respective toponymic lists. 187 

The aspect that remains of primary concern is the identity of the places at the beginning and end of each of those statements. The positioning of those termini, as argued throughout this essay, formed the basis for the fully-fledged portolan chart. Clearly, not all the possible termini would have been included among the Liber’s 196. But we can be fairly sure of the converse, that all those which were included had been placed, in an identifiable manner, on the cartographic document from which that information was copied.

The most important point about the Liber’s pelagic statements is the light that they may throw on the hypothetical document that had provided the author with that information. Because of the Liber’s incompleteness and the author’s occasional references to personal experience, it is unlikely that he was merely copying an earlier text. Indeed, it is not impossible that it was the sight of a (presumably rare) chart-like object which had provided the spur for the Liber’s compilation in the first place.


Table of Contents


For brief summaries see the Conclusions


 

E.5.   THE REAL MEANING OF THE LIBER’S ‘PELAGIC’ STATEMENTS


E.5a. How do we know that the statements could not describe actual pelagic courses?

The LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v)’s supposed pelagic statements comprise two elements: distance (in milliara) and direction (using a simplified mental wind compass). These link 196 pairs of places or natural features, usually positioned far enough apart to have required an open-sea voyage. The past assumption, which I had endorsed, was that the pairs of named places were pelagic termini and hence descriptions of actual sailing routes . But is there any real evidence that they had a direct connection to pelagic voyaging – despite the unambiguous use of the Latin term for open-sea (pelagic) voyaging, ‘transfretus’, a convention that continued for centuries 188 – rather than just citing the points that book-ended a theoretical journey? We need to re-evaluate the nature and function of those statements, and consider afresh where they came from, since understanding that point is essential for any coherent explanation of the portolan charts’ origin. It will be argued that those statements do not literally describe pelagic courses at all, whether directly experienced or conjectural.

It is not hard to demonstrate that whatever the purpose behind the Liber’s list of pelagic statements, it could not have been intended as a record of real voyages. A hint of this is revealed in the maps accompanying Joaquim Alves Gaspar’s 2019 Imago Mundi article 189 which create a pattern reminiscent of early-20th-century world maps with their straight, or elegantly curving lines denoting steamship routes. Long, open-sea journeys in the Middle Ages were neither straight-line or direct, nor without intentional deviations for victualling, etc. 190  Furthermore, as was pointed out by Patrick Gautier Dalché and others, a few of the Liber’s statements describe passages that are physically impossible because they pass over land. 191 

But even without those ‘smoking guns’, if the Liber’s author had been attempting a simple summary of what wind was needed to get from A to B, and how many miles might be involved, he would, in a number of cases, have had to show paired versions of that route, one perhaps with a favourable wind and – if it was feasible at all – another in the return direction involving a sequence of zig-zag tacking moves (or beating). Indeed, that could sometimes entail taking a different route altogether (for example in the eastern Mediterranean). Additionally, some routes were suitable only at certain seasons. Thus, any functional listing of pelagic courses would need to have been bi-directional and backed up with explanation.

E.5b. Why the Liber’s pelagic statements must have been copied from a cartographic document

Despite the fact that the Liber’s statements do not describe literal courses, the places named would almost certainly have served as the termini or staging posts of genuine voyages. Further, one of the important conclusions that emerged from Gaspar’s recent cartometric analysis of the Liber’s statements was that they were broadly realistic, not as a record of real routes but in terms of their positions relative to one another. 192  In other words, they must be reflecting the experience of mariners, because no landsman would have been able to imagine the shape of the Mediterranean or the interrelationship of its islands and mainland coasts, and no prior map would have supplied that information. From which it can only follow that the source for those statements was a cartographic document.

This is not, however, a wholly new interpretation. Patrick Gautier Dalché had emphasised the probability that the pelagic data must have come from a chart, 193 and Roel Nicolai concluded that “The bearing and distance data in the Compasso de Navegare’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) and, by implication, in other extant medieval Mediterranean portolans, have been scaled from one or more existing charts.” 194  Gaspar explained how “the author states clearly that he is about to describe the Mediterranean in writing and not, it is thereby understood, graphically. The likely reason for him to call attention to this detail is that the Mediterranean had already been described in a drawing.” 195  From this it is fair to conclude that, to some extent, a pointer to the portolan chart’s origin has been ‘hiding in plain sight’ in the Liber’s ‘pelagic’ statements. Gaspar’s confirmation of the meaning of those statements is a crucial finding for the origins debate.

In considering the content of that putative source map, the list of termini noted in the Liber 196 seems, at first sight, to be a relatively sparse and uneven selection. Some omissions are surprising – Genoa, Pisa, Naples, Barcelona, Algiers, Corfu and Ragusa, for example – and there is just a single pelagic route shown out of Alexandria, whereas Tripoli (Libya) is the terminus for four transits [Powerpoint, Slide 12]. This appears to emphasise that the author’s source(s) were mariners who favoured navigational relevance (mostly capes) over mercantile importance (harbours). When ports are included, for example in the Levant and along the north coast of Africa, those tend to be in areas lacking prominent headlands. But, does the limited number of entries mean that the Liber’s list should be interpreted as only a partial copy of a longer one?

A close look at the distribution of the termini on Gaspar’s map 197  indicates that it is certainly not random. Broadly speaking, it provides an overall coverage. Nor can it be said that the Liber’s list of termini is lacking in detail. Cyprus, key to navigation in the eastern Mediterranean, is the terminus for no fewer than seven transfretusLong-distance, or pelagic, courses usually out of sight of land tracks. That the Adriatic and Aegean are largely ignored fits in with the reality that navigating in both seas was probably never out of sight of land, hence pelagic directions would not have been needed. More surprising, perhaps, is the paucity of names down the west coast of Italy, the very region assumed to be the charts’ birthplace. Yet it was from Corsica and Sardinia rather than the mainland, and by using the Strait of Bonifacio that divides them, that those pelagic voyages to Spain and beyond would have effectively started. To emphasise that point, Sardinia’s south-west point, the Isle of S. Petri, features in five of the Liber’s statements, 198 whereas all that island’s ports are ignored.

Once it is accepted that the Liber’s pelagic data could have derived only from some kind of cartographic document, it is hard to conceive how that could be other than a very primitive portolan chart, or the geometric diagram being proposed in this essay as the ultimate source for that. Crucially, if it is agreed that a hypothetical cartographic document supplied the Liber’s information, that must push back the charts’ origin to a period earlier than the current estimate of the date of the Liber’s content (no later than 1210). This corroborates Nicolai’s statement, based on a study of Lo compasso, that “Portolans of the Mediterranean and Black Sea were scaled from portolan charts. Therefore portolan charts must have existed before the extant portolans of the Mediterranean were compiled”. 199 

However, the significance of Gaspar’s revelations goes further because his cartometric analysis found that the majority of the Liber’s directions had seemingly been determined by traditional astronomical methods rather than the use of a compass (because they were “not affected by any systematic error caused by magnetic declination”). 200  Hence, the Liber’s 196 pelagic statements could prove to be the key that helps unlock the long mystery of the portolan chart’s origins. And it is fitting that what seems to be our first reference to a prototype marine chart helps to confirm the existence of a body of knowledge derived from open-sea sailing based on the relative positions of pelagic termini, corroborating, simultaneously, both the charts’ origin and their purpose.

The identifications of the places mentioned in the Liber’s pelagic statements have been supplied by Gaspar 201 but the locations of the termini are naturally taken from an accurate modern map. Plotting out the Liber’s straight-line direction and distance formulae (with adjustments for those that exhibit magnetic variation) against, first, a modern map and, second, the Carte Pisane Accepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) might be a way to test the interpretation of the origin and meaning of the Liber’s statements. Would there be sufficient conformity between the plotted positions of the Liber’s pelagic termini and the equivalent ones on the Carte Pisane, and likewise between their respective choices of those terminal points? If such an exercise was feasible we might then be allowed a partial and indirect glimpse into a very early stage in the chart’s development, and thus come closer to the actual origin than we are likely to achieve by any other means.

E.5c. How were the Liber’s pelagic statements constructed?

In the absence of evidence, how those pelagic statements were formulated has to be left to conjecture. Logic suggests the following stages.

The relevant information would have had to be retrieved and then ‘translated’ from a graphic document into text. The procedure would not necessarily have been straightforward. First, the places at either end of the line would need to be identified (presumably by a process of authorial selection) and then the distance between them measured. That would have required a ruler whose scale was calibrated for the portolan mile. Ideally the ruler would have been long enough to reach across the chart so as to avoid having to add up figures. Unless such a ruler already existed at that very early stage, which seems unlikely, the author would have had to know (or find out) the length of a portolan mile before he could create a relevant tool. 202  Once the measurement had been made, the figure would then be rounded up or down, according to a pre-agreed principle. 203 

The most demanding stage would have involved deciding how to describe the bearing in the appropriate coded form. Furthermore, directions could not just be measured off; they had to be estimated. Any pelagic diagram would, of necessity, have had bearings at its core. Indeed, it seems highly likely that the hypothetical diagram would have been constructed over those directions, making it probable that a network of direction lines was already present. If so, the logical arrangement would have comprised a central point with lines radiating out systematically in (perhaps) 16 directions (the half winds) as seen on the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . The Liber’s direction expressions do not stop at the half wind (although quarter winds are not named) because the author uses a variety of refining expressions to convey extra precision beyond what could be read off a map with an underlying 16-point compass network. 204 

Since the Carte Pisane gives us our first indirect glimpse of a portolan chart, it is worth noting how its clumsy attempt at providing full directional coverage for its compass lines meant that some areas remained outside it. Had the Liber’s author been working from a chart of a similar design that would have made extracting directions more complicated. However, it was the use of two large compass circles that had created the Carte Pisane’s difficulty. Perhaps, in the earlier period, the supposed geometric diagram might have had just a single circle and thus largely avoided that problem. 205 

We need to remember that although the pelagic statements in the Liber are of immense historical importance for the origins debate, they can be relied upon only for the names of the chosen termini. The other information, the distance and direction of each of those theoretical courses, comes down to us mediated by that unknown, non-nautical writer or any copyist who might have been involved.

E.5d. The discrepancies between the stated pelagic distances in the Liber and Lo compasso

An issue that seems not to have been previously discussed concerns the discrepancies between the mileage figures given in the Liber and those in Lo compasso. Patrick Gautier Dalché's edition of the Liber includes a list of the pelagic 'courses', paired, in a surprisingly small number of cases, with the equivalents in Lo compasso. 206 

A few of the most striking disparities follow. The figures are preceded by the relevant line number in the Liber:

337. C. Maone (Majorca)-Bugea/Bejaya (Algeria) – 400 ml. (Liber), 320 mil. (Lo compasso)
412. Tripoli (Libya)-Lampedusa island – 250 (L), 400 (Lo c)
432. Bonandrea-Rasausen (both in Libya) – 60 (L), 100 (Lo c)
1146. Bocca d’Avedo (Dardanelles)-C. de Sirofa (Euboea, Greece) – 400 (L), 200 (Lo c)
1235. Mallea Mattapane (Greece)-C. Spade (Crete) – 70 (L), 110 (Lo c)
2165. Gozo-Resautino 400 (L), 200 (Lo c) [both say north-south, i.e. not confused with Godi (off south-west Crete), another common terminus]
2266. C. Taolato (Sardinia)-I. Maremma (I. Egadi, Sicily) – 400 (L), 280 (Lo c)
2352. S. Pietro (Sardinia)-Bugea/Bejaya (Libya) – 210 (L), 320 (Lo c)

Besides the surprising disparity – double in one of the longest cases – the larger figures might have been provided by either. In other words, it was not simply a question of the use of different scales. Furthermore, two of the longer tracks are given equivalent figures (taking into account the Liber's less precise rounding of the figures):

2137. C. Baffe-C. Salmonis – both 400
2214. C. Passereis-C. Spade – 700 (L), 720 (Lo c)

To explain those discrepancies would require the testing of all the examples identified by Gautier Dalché against true distances. There is a further, related question. The authors of the Liber (almost certainly) and Lo compasso (probably) derived their distances by measuring from a cartographic document. One outstanding question for future research would be to ask when the mileage figures in the portolani started to be repeated by scribes rather than being measured off a chart, presumably with differing results. Another would test whether subsequent copying introduced corruption in the mileage figures, and, if so, whether those could be used to help trace the lineages of later portolani.


Table of Contents


For brief summaries see the Conclusions


 

F. SOURCING THE PELAGIC DATA

 


 

F.1.  HOW WERE DISTANCES MEASURED?

It is not until the 15th century that detailed references are made to distances and speed at sea. 207  Nevertheless, it would not have been possible to have created a portolan chart without agreement about measurement. References to statements in terms of ‘miles’ or measured mileages recur regularly through the various sections of this essay and, for convenience, are brought together here.

As a result of Joaquim Alves Gaspar’s confirmation that the pelagic statements in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) must have been measured off a chart-like object rather than being copied from a text or passed on orally 208 it is necessary to consider two important issues which do not seem to have been previously addressed in the literature on portolan charts: first, how did the medieval pelagic sailor measure and describe distance and, second, was the primary measure miles or, alternatively, hours/days? Those alternatives will be examined shortly in section F.1b ‘Measuring distance in terms of time or miles’.

As already mentioned, each of the Liber’s transfretusLong-distance, or pelagic, courses usually out of sight of land entries includes the distance involved. These are stated in milliara: ‘ml.’ or ‘mil.’ (or just assumed), and in ‘mil’ (for millara ) in Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396). It is evident that those crude statements would have been of little use for mariners, who would either have held the real courses in their memories, along with the necessary accompanying details, or, alternatively, would have needed a graphic image that placed the two termini for a planned voyage, and the intermediate waymarks, into the wider context.

First of all, the rounding up of the mileage figures in both of the portolani, and especially the Liber, reveals approximation on the part of the person extracting them from the conjectured chart or diagram. The smaller figures in the Liber are rounded to the nearest 10 miles, the medium links to 50, and the longer courses to the closest 100. For that reason, Lo compasso’s measurements of 7 miles for the distance between Trapena and Evinza compared to the Liber’s 10; the figure of 190 rather than 200 for Porta d’Evinza – C. de Pali; or 720 for C. Passaro – C. de Spata instead of the Liber’s 700 – to give three examples – may merely point to a little more precision on the part of Lo compasso’s compiler. 209 

F.1a. Arabic numerals

It has been generally assumed that carrying out calculations in Roman numerals must have been inefficient; the Arabic decimal system, with its all-important zero, would surely have been far more practical. Ramon Pujades made that point forcefully, stressing the significance for the portolan-chart origin debate of the introduction of Arabic numerals into the Christian world by Leonardo Fibonacci from Pisa. Even if Pujades’s view was accepted, that aid would probably not have been available to the portolan charts’ creators in the suggested period, namely the latter 12th century. Fibonacci’s explanatory text dates from 1202 but, even if Pisan merchants were the earliest to adopt those numerals (and the Liber’s author was also Pisan), their widespread use – as plotted by Pujades – did not occur until the late 13th century. 210  The Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) already reflects that revolution in its scale markings, although its system contains five smaller divisions rather than ten.

Although it might be hard to see how a mathematical device such as the toleta de marteloio‘A trigonometric reduction table to aid navigation by dead reckoning’, used to calculate the actual course sailed when tacking into the wind could have been fully effective without Arabic numerals, it has been argued that those assumptions are misplaced, and that “Roman numerals are not only informationally equivalent to Arabic ones but also computationally similar”. 211 

F.1b. Measuring distance in terms of time or miles

Calculating distance could have been done in various ways. Among the likely methods would have been keeping an account of elapsed time, estimating the ship’s speed, observing the passing coastline and relating that to known distances, as well as other personal yardsticks.

It seems clear that during the classical and medieval periods short hops along the coast were usually expressed in terms of miles, but that did not apply to the longer stretches and particularly those that took the ship out of sight of land. As Barry Cunliffe pointed out, “The ancients thought in terms of a day’s sail in a fair wind”. 212  This was also the practice with the earliest Arabic itineraries in the 10th–12th centuries, where 'miles' were used only for distances along a coast, whereas in the 11th-century Book of Curiosities An Arabic manuscript of the 11th century including maps and descriptions of the Mediterranean, but not related to the portolan chart – see Section A.3a, and Rapoport & Savage-Smith, 2018 , for example, longer distances are measured in the number of days and nights required for sailing. 213  Likewise, Pliny’s 935 nautical mile journey from Rome to Gibraltar was reported to have taken took him seven days, at what must have been a rapid 5.6 knots [a knot, or marine mile, is 1.15 standard miles]. But, as might be expected, this was described using the inexact measure of whole days, rather than miles. 214 

In today’s world, measurement of time is ever-present, sometimes with a precision far greater than most people need. But medieval sailors would have had to rely on dead reckoningEstimating the direction and distance travelled by relating the ship’s apparent speed through the water to the elapsed time, so as to find the position at sea and their mental clock. The other important factor, the speed through the water, could have been partly measured with a log line, or perhaps the mariner simply sensed it. A valuable aid would have been the hourglass (or sand clock) but that invention came too late for the portolan charts’ creators. The device is not recorded until a Barberino manuscript of 1306–11 and it is first depicted on a Sienese fresco of the 1330s. 215  Even if the hourglass had been known a century earlier, it was an inexact device and easily disrupted by moisture or the roll of the ship. In addition, its usefulness would have depended on constant checking, perhaps every half-hour.

It would obviously have been easier to measure distance in terms of days’ sailing rather than calculating the mileage covered at sea. If so, one of the charts’ functions might have been to enable the navigator to compare a stretch of known duration from a previous voyage with the new course on which he was embarking. It is also possible, following that suggestion, that the initial estimates that went into the construction of the conjectured pelagic diagram might have had to be based on elapsed time rather than calculated distance.

Although it is unlikely that the regular measurement of the ship’s progress would initially have been envisaged in terms of miles rather than passing time, there could have been occasions when the temporal measure did need to be converted into estimated miles. Periodic totals would presumably have been calculated (whether hourly, for a whole day’s sailing, or a full 24 hours) so as to plot the progress across the chart (if only visually) or against memory. If those sub-totals were retained and added up, the result at the end of the voyage would have been an estimated overall pelagic reckoning in miles. But that would only have been realistic if each recorded figure represented the helmsman’s best estimate of the distance gained along the straight line of the planned route, rather than what would usually be the considerably longer mileage that included the zigzags when tacking. To have obtained the shorter, direct figure, the navigator would have had to use the toleta de marteloio‘A trigonometric reduction table to aid navigation by dead reckoning’, used to calculate the actual course sailed when tacking into the wind or its mental equivalent, which presumably depended on mileage figures.

The other overwhelming need for mathematical rather than temporal mensuration would have been in connection with the creation of the portolan charts themselves. The diagram needed to underpin the chart’s construction could not have been built up around measurements expressed in terms of days’ sailing. That does not undercut the new understanding that the use of mileage figures for the long courses in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) cannot be interpreted as reports of actual measured voyages. 216  Indeed, once the Liber’s pelagic distances are reinterpreted as straight lines instead of actual voyaging routes, the use of miles rather than time makes complete sense. As is argued in this essay, whereas the pre-chart mariner might have carried in his memory rough estimates of overall distance, their refinement would only have become possible once the hypothetical rectification process had taken place during the initial development of the portolan chart.

Thus the mileage figures between the Mediterranean’s numerous pelagic termini should be seen as deriving from a process of mental triangulation, followed up by adjustments – both ’inadvertent’, in the sense that no conscious mathematics was involved – rather than coming directly from sailors’ memories. 217  Generally speaking, long-distance measurements in miles would have been purely cartographic statements, with limited navigational relevance. It is unlikely that those were ever shared orally or had a life outside the marine chart or the written page.

F.1c. Scale(s) of the portolan charts

Scale (i.e. literally relative distance, or, in practice, probably measures of elapsed time, as discussed in the previous section) was not a luxury for the portolan charts. It was fundamental to both their creation and use. For pelagic courses to have defined the coastal shape of the Mediterranean, distances would not only have to be expressed numerically but also according to an agreed length for the ‘portolan mile’.

‘Scale’ in this discussion can have different meanings:

1. The representative fraction

That is the ratio of the distance between two features on the chart and the equivalent in reality. Today, the way we express the scale of the average portolan chart is as a representative fraction, ranging between 1:5.5 million and 1:6.5 million. 218 

2. Scale bar

The length represented in the real world by a measurement on the portolan chart is normally shown – though without explanation – by means of a graduated scale bar, as can be seen on the oldest chart, the Carte PisaneAccepted as the oldest surviving portolan chart, c .1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) [Powerpoint, Slide 13].

The measurements on the two portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes are stated in ‘miles’. This is likely to relate to the medieval Italian miglia, itself based on the Roman mile of 1,000 paces, each of five feet (Agrippa’s own). The precise length of a portolan mile expressed in modern measurements remains elusive. 219  It seems more likely that most sailors would have ignored actual measurement and instead developed their own yardstick based on a section of coastline well known to them, which, by using their fingers, was transferred to the chart and the requisite number of the scale’s divisions read off.

3. Regional scales

In order for the single scale measure indicated on a portolan chart to have had any usefulness there had to have been some means of achieving an initial general agreement as to the length of the ’portolan mile’. This would have been particularly important in the period during which the underlying geometric structure, posited here as the source of the portolan chart, was being formed and corrected. The Carte Pisane’s relative precision (and presumably that of its forerunners as well) could not have been achieved had local or personalised versions of a mile been used. The Mediterranean’s shoreline presents one continuous boundary between sea and land, created by nature and ignoring human divisions; the unit of measure that was being used must have done likewise.

Despite that, although the Carte Pisane (and those that followed) display a single graphic scale to cover the whole chart, we know that some areas were actually drawn at different scales. It had been thought that there was a simple tripartite division: smaller scale in the Atlantic, ‘normal’ scale for the Mediterranean, and an enlarged scale for the Black Sea. 220  This disparity was refined by Gregory McIntosh and Gonçalo Dias in a 2018 paper which showed, via cartometric analysis, that there were five different scales, respectively, for the Atlantic, the main body of the Mediterranean, and, separately for the Adriatic, Aegean and Black seas. 221  However, Roel Nicolai describes a still more extensive division into six sub-regions (the north and south Atlantic coasts, the western, central and eastern Mediterranean, and the Black Sea) each with its own coherent scale and orientation. But, surprisingly, he finds that those do not coincide with the recognisable boundaries of the sub-basins in the Mediterranean. 222 

The presence of these regional variations was not apparently recognised by contemporaries until Francesco BeccariFrancesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library, Art Object 1980.158) included a remark on his chart of 1403 to the effect that he had corrected the understated Atlantic scale. That can probably be explained by the fact that the Atlantic outlines were evidently omitted from the earliest charts, since they appear in very rudimentary (essentially hearsay) form on the oldest survivor, the Carte Pisane. The other scale variation – increased in that case – concerned the Black Sea, which already appears on the Carte Pisane. However, as is argued later 223 the Black Sea outlines were added during the 13th century to an already existing chart. Thus the separate scales for the three main regions, point to the earliest (lost) charts having initially focused on the Mediterranean, and that the later addition of the two neighbouring regions was done without adequate coordination in either case. 224  These variations in scale are fully understandable, if the portolan charts’ geometry is accepted as being based on remembered pelagic courses rather than measured survey. Likewise the two main basins within the Mediterranean, the Adriatic and Aegean, with scales of their own, could not have been easily incorporated into the hypothetical rectification process we are proposing because there would have been too few overlapping courses. 225 

When latitude scales were introduced onto marine charts after 1500, and various European maritime powers spread their sphere of influence beyond the Mediterranean, the value of the leagues used by different countries diverged, and sometimes multiple scale bars were provided. But the portolan charts did not include such a device. 226 

F.1d. The conceptual issues involved

Who was likely to have been interested in the theoretical consideration of measured distance rather than the practical one of duration? A simple statement of distance and direction like those in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) could have been of little practical use on a journey, over several days, and involving a sequence of dog-leg changes of direction, whether for navigational reasons or in order to obtain provisions. Perhaps Pliny’s crew on his journey from Ostia to Gibraltar might have been interested to have learnt that 935 miles was going to be involved rather than a rough measure of about seven days. But how would they, or their medieval successors, have been able to recognise or measure those miles?

There is a new consensus growing around the conviction that the measurements in the Liber’s pelagic statements would have been copied off a cartographic document, which ipso facto must have preceded it. But despite the use of miles in those statements it does not follow that navigators were already talking about measured distances and holding mileage figures in their heads. Only at a certain stage in the combining of the shared pelagic memories would there presumably have been enough trust in the positional accuracy for that to have happened. However, the further inference would be that the precursor portolan chart, seen and used by the Liber’s author, had already achieved sufficient sophistication to provide those fairly realistic measurements which could then be reproduced in textual form. In other words, it can now be further claimed that distance statements in terms of miles rather than time would have only become meaningful once there was a realistic outline for the Mediterranean and its islands – based on pelagic termini – so as to provide the necessary authority .

Once that document – even if it was no more than a pelagic diagram – had been drawn and distributed, it would have permitted any user, however unskilled, to take measurements between two points in actual ‘miles’, which could then be translated into estimates of days’ sailing. For all its merits, the Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text, 227 with its distorted coastal outlines, could never have been used in that way.

To use ‘miles’ – regardless of what their actual length was thought to be – whether to calculate the distance involved in a projected voyage or measure what had already been covered in the present one, is a far more sophisticated concept than using hours or days as the yardstick. It requires computation. Anyone looking at the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) (or its lost predecessors) would have had to understand that the unexplained scale diagram – formed of a circle containing a horizontal line bisected by a group of 20 small vertical lines, alternatively in red and black – represented ‘portolan mile’ divisions, with a pair of widely spaced dots beyond that denoting wider extents. To have made use of that ruler, the mariner would have additionally needed to know that this was a partially decimal system, with the smallest divisions representing five miles, and hence the group of ten covering 50 miles 228 [Powerpoint, Slide 13]. If the sailor was computing distance from the scale bar, it might be supposed that he could have picked up the 50, 100 or 200 mile stretches with his fingers and then used those, or multiples of them, for planning a pelagic voyage. But it is reasonable to question whether the earliest users of portolan charts actually thought in terms of measured ‘miles’ at all, rather than extracting their own personal baseline measurement by spreading thumb and index finger (or a whole hand span) along a well-known section of the coast.

The foregoing throws up an interesting, but possibly unanswerable question: did a generally accepted portolan mile exist prior to the charts or did it emerge as part of the rectification process that gave the charts their geometric underpinning? If the former, how does that fit in with the origin theory (to be discussed shortly) that posits ‘separate basins’ (and not just for the Adriatic and Aegean), 229 given that those would have inevitably involved local customary scales? As was pointed out in the previous section, there are indeed several different scale units, co-existing, unrecognised, on the early portolan charts. Even if, as is often assumed, the classical unit for a marine mile was preserved through all the intervening centuries, it is surely likely that it was the portolan chart that introduced that common measure, the ‘portolan mile’, at least to the open areas of the Mediterranean, as a visible standard instead of being just a mental concept.

.

Table of Contents


For brief summaries see the Conclusions


 

F.2.  THE IMPORTANCE OF LANDWARD VISIBILITY

A diagrammatic chart recently devised by Joaquim Alves Gaspar showing the areas of the Mediterranean and Black seas where land might be visible (in grey), or would certainly not be (in black), 230 [Powerpoint, Slide 14], invites a fresh interpretation of the ways in which the positioning of the defining features of the coasts might have been captured. Within the considerable expanse of grey shading some (if not most) of the coastline would have been visible to the mariner in an average-sized ship. When coastal mountains were involved, the effective range would be significantly increased. 231  In some cases, such as the Adriatic and Aegean, and offshore islands elsewhere, land might be viewed in more than one direction, perhaps in several. Those cases, where land was constantly in sight, could have readily supplied a partial framework. However, no land at all would be seen in the black-shaded areas. As Gaspar explains:

“For over perhaps one third of the Mediterranean Sea land is out of sight even in optimal atmospheric conditions. The area involving the greatest problems for early long-range navigation was the eastern Mediterranean, especially for routes linking southern Europe and its islands with the African coast.” 232

It is those black zones, where no land would have been in sight, which held the key to any attempt at charting those seas as a whole. 233  Positioning the termini of those truly pelagic routes was the essential element that made a sufficiently realistic portolan chart both possible and necessary.

I am not aware of any previous categorisation of areas of the Mediterranean and Black seas, into, respectively, those with many simultaneous land sightings, others with limited or possibly no more than a single view, and those where the crew had no land in sight at all, sometimes for days on end. I may well have missed any such tripartite classification, effectively a refinement of Gaspar’s schema.

Might these alternative levels of visibility have translated into different ways of recording what had been seen or surmised? For instance, running along a coast with no land visible on the seaward side of the vessel (the eastern half of the North African coast is a good example) would have favoured a simple coastal survey, although there would have been nothing to test its distances against. For those parts of the grey zones where two or more land features were in view, this could have led to a partial and intuitive type of what is being suggested here as ’inadvertent triangulation’An invented term for the hypothetical process by which pilots, before there was a marine chart, could have built up a mental network of the interrelationships between Mediterranean headlands, by means of observed directions and estimated distances. No mathematical calculations would have been involved. To document the black zones – i.e. define their limits, since there would be nothing within those that could be recorded on the featureless sea – I am contending that the only plausible source for that would have been the sailors’ mental maps and estimations of distance, formed from personal and second-hand experience. 234 


Table of Contents


For brief summaries see the Conclusions


 

F.3.   THE ‘SUB-CHARTS’ HYPOTHESES

Among the theories arguing against the portolan charts having arrived fully formed, 235 has been the repeated assertion that they were created by combining pre-existing regional charts, whether defined by specific Mediterranean basins or in other ways. A few proponents of this theory can be cited; no doubt others have been overlooked.

The first instance seems to have been Hermann Wagner’s statement in 1895 that the “creative achievement of the Italian cartographers may be seen first of all in the correcting and assembling of older charts of the different basins so as to form a complete picture”. 236  Two years later, Adolf Erik Nordenskiöld elaborated on that idea 237 and it was further promoted by Konrad Kretschmer in 1909. 238  Then, in 1987, David Woodward set out a new theory (which, as he explained, had still to be tested) based on a line between Tunisia and Sicily, which divides the Mediterranean into western and eastern halves, each with their own distinct basins:

The cumulative experience of several centuries of coastal and other shipping in each of these basins could have led to the independent recording of traditionally known distances. It is probable that navigators in the Mediterranean during the late medieval and Renaissance periods used both coastal traverses and cross-basin routes. The average distances derived from these sailings between pairs of ports – both along the coast and across the sea – could then have been used in the construction of a series of separate charts of the individual basins. If these routes were plotted to form networks in each of the basins listed above, each network might have assumed the form of a self-correcting closed traverse approximating the shape of each basin [my italics]. The rigidity of this structure would, however, have depended on the availability of the cross-basin distances, acting as braces to the framework. It is thus postulated that some system of empirical or stepwise graphic method of correcting these frameworks was used to achieve a ‘least-squares’ result. These discrete compilations could then have been amalgamated into charts of the entire Mediterranean. 239 

Since 1987, cartometric analysis has developed considerably and it has been applied to the portolan charts by a number of investigators. 240  The most thorough study was that by Roel Nicolai in 2014. He identified the composition of the portolan charts as forming a mosaic of separate sub-charts, comprising six sub-regions (respectively, the north and south Atlantic coasts, the western, central, and eastern Mediterranean, and the Black Sea). He found that each had a coherent scale and orientation, even though the “Sub-charts appear to have been fitted together based on overlapping stretches of coastline”. 241  By overlaying those proposed divisions over a 1466 Petrus Roselli chart he demonstrated their extent. 242 

Most recently, Joaquim Alves Gaspar’s cartometric analysis identified the portolan chart as compiled from the assembling of at least three separate regional outlines. These covered the Atlantic; the western Mediterranean (west of about 20° E) [compare that to Woodward’s division at around 12° E]; and the eastern Mediterranean and Black Sea. He discerned ‘stitching errors’ in the north Aegean Sea and in the eastern part of the Gulf of Sirte. 243 

We first need to clarify the terms used above: namely, ‘basin’ employed by both Wagner and Woodward, and ‘regions’ and ‘sub-regions’ used by Gaspar, as well as Nicolai, who distinguished two of the terms, noting that the “joins between the sub-charts do not always coincide with the natural boundaries of sub-basins in the Mediterranean”. 244  Two of the sub-divisions, the Adriatic and Aegean, are clearly defined, discrete seas, as, likewise, are the Black Sea and the Sea of Azov. But what of Woodward’s other ‘basins’: the Alboran, Balearic and Tyrrhenian seas in the western portion of the Mediterranean and, in the eastern half, the “basin surrounded by Asia Minor, Syria, the Holy Land, and Egypt”? 245 

When considering the Woodward/Loomer, Nicolai and Gaspar analyses some obvious questions arise:

The different sub-charts theories are united in asking us to unite behind the contention that there was an ability among medieval mariners to ‘survey’ discrete sections of the sea – even though they would have sailed unknowingly across those proposed divisions – and then interlace those to form a comprehensive whole. But you cannot divide up the open sea in a meaningful way, any more than you can partition a sandy desert, unless you have instruments of the kind unavailable in the Middle Ages.

In essence, the sub-charts hypothesis (or hypotheses, since there does not seem to be unanimity about the details) depends on arbitrary divisions of the open Mediterranean. It is not made clear who might have decided where to draw the boundaries, and how, realistically, they could have done that. Nor why anybody would have wanted to perform that operation anyway. We can reasonably assume that a medieval pilot was concerned with courses, leaving the identification of regions, areas or zones to the geographers. It is worth noting that the names of the seas – which in some cases have had varied forms, whether at any one time or through the centuries – are not included on the portolan charts. Indeed, it is unlikely that the medieval mariner would have been concerned about those subsidiary seas anyway. 246  More specifically, there is the issue of how any theoretical slicing up of the Mediterranean can be squared with the extent of the complex, comprehensive coverage revealed in Nicolai’s diagrams of the pelagic statements in Lo compasso. 247 

That process of creating sub-divisions of the Mediterranean pre-supposes having a conception of the whole sea. Otherwise, it is akin to trying to complete a jigsaw, made up largely of blank pieces representing the open sea, without a formal, containing border of any kind to show the sea’s extent, and with the key picture for the puzzle having been lost. Since it is always difficult to imagine what it was like before we became aware of something, try attempting mentally to complete a jigsaw featuring a section of the far side of the Moon for which no image was made available, without having any idea of the puzzle’s size, shape or how to recognise its edges. We must never lose sight of the fact that nobody could have known the realistic shape of the Mediterranean or the way its parts connected until the geometric underlay for the portolan chart had been drawn out. Unless, in perhaps a few cases, a highly experienced pilot held a sufficiently complex overall chart in his memory.

The sub-charts thesis, in the way it is being presented, is a theoretical, quasi-mathematical and surely anachronistic solution to what appears to be an imaginary problem. It imposes arbitrary boundaries across the featureless sea, in wilful dismissal of the routes sailors were routinely taking. Those proposed open-sea sub-divisions would have been invisible to sailors and irrelevant for navigation. By promoting these (putative) sub-divisions – in other words regionalising this issue – the integrative, co-operative, holistic approach, which unites rather than divides, and which alone could have resulted in a coherent overall marine chart, is cast to one side.

The arguments put forward in support of the sub-chart explanation for the portolan charts’ origin rest on (sometimes differing) cartometric analysis, but lack historical backing. Mathematical reckoning, with its ability to manipulate data and suggest patterns may say one thing; human judgements based on deliberative thought another. Even if those findings were not challenged, their continued acceptance would require a plausible explanation of how such sub-charts might have been created and how the medieval pilots could have fashioned a sea-wide chart out of them. That also leaves unresolved two further questions: first, how that information might have been gathered, since it deals with geographical divisions rather than the areas that would have coincided with sailed experience; and second how those regional maps might have been disseminated away from the usual monastic and scholarly routes.

Ramon Pujades has been the most assiduous among contemporary students of portolan charts in chasing down material in the archives. His refutation of the sub-charts theory is worth repeating in full:

So that medieval mariners might have put together the partial maps of the different basins that comprised the Mediterranean – which it is assumed they did on board the vessels that sailed each sector of the coast – this type of map would have had to circulate with relative frequency, thereby making it possible to copy, purchase or exchange maps of the different sections until a picture of at least a substantial part of the Mediterranean coastline could be drawn. However, no reliable traces, either direct or indirect, exist that would support the arguments of those who defend the theory… Not even a fragment of this kind of partial map that is assumed to have preceded the creation of complete charts has come down to us, nor do we have any indirect references in documents or chronicles of their existence. 248 

The preceding can be endorsed with the observation that whereas the lack of traces of the hypothetical mental map was of course inevitable, the parallel absence of the conjectured regional charts, as graphic artefacts, or of any written references to those, is harder to defend.

But, more to the point, the idea of different groups of sailors, spread out across the Mediterranean, simultaneously working up regional charts around the year 1200 is clearly fanciful. The portolan chart was primarily of use to pelagic sailors and must logically have been prepared for them. 249  It had little to offer those plying the cabotage trade, who would already have a far more detailed knowledge of the coasts and toponyms than any chart could have provided – people like Chaucer’s shipman. 250  It is hard to envisage such localised surveying activity. Was there a separate group to match each of the projected sub-divisions of the Mediterranean? If their activities would only have made sense once all those surveys had been joined up, somebody would have had to supply the overall vision in the first place, and then coordinate the process of distribution. Furthermore, there can certainly be no justification for dividing out the portolan charts’ extraordinary innovations 251 among such imagined local groups.

The main weakness of the sub-charts theory – and there are several – is that it posits a number of regionally focused efforts, presumably aimed at local needs, somehow morphing into what was totally different, and wholly unprecedented, namely a universal picture of – to a medieval sailor – their entire world.

F.3a. The Adriatic and Aegean

On the other hand it is logical to consider two of the Mediterranean’s basins separately from the other bodies of water (which are partly or fully open), namely the Adriatic and Aegean Seas. These are clearly defined sub-basins, which, as a result have their own distinctive characteristics and hydrographic history.

As deep gulfs, the outlines and internal details of those two seas must have been gathered independently from the rest of the Mediterranean. In the first place, the narrowness of the Adriatic provided continuous intervisibility, aided by the complexity of its eastern shores, where there are 1,300 islands and islets. The Aegean Sea is likewise cluttered with islands. 252  This would have made it very difficult if not impossible, either to relate the prominent features of those two basins to the open seas to the south of them, or to achieve the internal locational precision that was managed elsewhere.

This interpretation would fit in with the contention here that, in terms of the pelagic network, those two basins would have effectively constituted cartographic backwaters, with little opportunity to benefit from the mutual reinforcements of the main network. It is not coincidental therefore that the overall structure for the Mediterranean as a whole on the Carte Pisane Accepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) was largely unaffected by the distortions caused by its narrowed Adriatic and elongated Aegean. Those would have fallen outside the unified system that bound together the rest of the Mediterranean, and particularly the large areas lacking any land visibility. The drafting errors involving the Adriatic and Aegean might seem to offer support for the separate basins hypothesis, but as genuine ‘basins’, they should instead be considered as exclusions from what is proposed here for the rest of the open Mediterranean.


Table of Contents


For brief summaries see the Conclusions


 

G. WHAT CAME FIRST?

 


 

G.1.  THE ‘CHICKEN AND EGG’ QUESTION OF PRIORITY: PORTOLANO OR CHART

Konrad Kretschmer was an early advocate of the ‘portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes first’ thesis, 253 and the idea was elaborated by Jonathan Lanman in his study of Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396). 254  We do not have any chart from the likely period of the compilation of the earlier Liber The ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) (c.1210) although its existence has been logically extrapolated. 255 

It is conceivable that there might have been an even earlier portolano with similar pelagic information, perhaps even preceding the first attempt at a graphical chart. Nevertheless, there are at least three investigatory routes that can usefully be followed, to test Joaquim Alves Gaspar’s assertion that: ”The idea that the earliest portolan charts were created from portolans, whether these were specifically for use by pilots or for the wider benefit of literati and patrons, has been long dismissed”. 256  The first approach establishes the separate development of text and chart, the second looks specifically at the parenting of the portolan charts, and the third considers the direction and distance statements in the coastal itineraries that comprise the bulk of the portolani texts.

G.1a. Separate development

As a rebuttal of a simplistic ‘chicken and egg’ debate, there is strong evidence that neither the portolan chart nor the portolano could have been largely created from the other. These are the main grounds for that assertion:

In addition, given the divergence between the place-name lists in, respectively, the Liber, Lo compasso and Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , and the separate developments those demonstrate, the Liber’s names could not have been copied from a chart, unless, and this seems unlikely, the Carte Pisane fails to reflect, in general terms, the toponymic content of any prototype chart that might have been seen by the Liber’s author some decades earlier.

There might well have been some interchange between those who compiled the texts and those who drew the chart but no direct connection is likely, apart from the partial sharing of toponyms.

G.1b. The parenting of the portolan charts

Like humans, it would appear that the portolan chart had two parents. Some previous historians considered that the charts were the result of a single creative process, even if sections might have been produced independently and then joined up. 258  But the contention in this essay is rather different. One ‘parent’, experienced pelagic mariners who provided the mental maps of long-distance courses, supplied the charts’ geometry; whereas the other parent provided the coastal outlines (and the toponyms ranged along them) which would have come from records made during coast-hugging journeys. The placement of the headlands and ports that served as the departure and destination termini for the pelagic courses must have been memorised without either textual or graphic forbears. But the recollection of those voyages could not have supplied the detailed local information gained by close observation of the coastline.

How (and when) might those two distinct elements have become conjugally united: first, fixing the nodal points which defined the geometric structure of the entire Mediterranean and Black seas, and, second, adding the littoral itinerary around their perimeters, which could have simultaneously supplied the coastal outlines and toponymy? A portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes without a chart would still have been useful for coastal navigation but the information it contains could not, on its own, have been used to draft a chart. 259  However, a diagram of the termini of the interlinked pelagic courses 259a could certainly have served as a framework into which the coastlines and place-names would then be inserted.

There is too much disparity between the two early portolani, and then again between them and the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , as well as too much uncertainty about their respective dates, to plot with any confidence just how these distinct elements came together to form the portolan chart as we know it. But why is there an assumption that writing (apart of course from the charts’ toponymy) would have played a part in the origin of a graphic document, particularly one like the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) , written in Latin by someone with religious connections and interests? 260 

G.1c. The coastal itineraries

The largest parts of both the early portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes comprise sequences of stated distances from one coastal place or feature to the next. All sailors would have known sections of the shoreline from their own experience. Many might have found that sufficient if they were merely repeating previous voyages. But some pelagic sailors would have needed to know the sequence of headlands and ports for the occasions when they reached a little-known coastline some distance from the place they were aiming at. Which way should they turn and how far or how long would the correction take? However, that is not likely to have provided sufficient impetus, on its own, for any systematic and comprehensive itemisation of the entire Mediterranean coastline.

Lacking evidence, we do not know how the different itineraries in the two early portolani were gathered, except that the process must have been carried out independently since, beside the major differences in their selections, they proceed in the opposite direction. Each could well have been a collaborative pooling of sailors’ memories. Additionally, textual itineraries, in the form of simple lists, certainly preceded the portolan chart. For example, there is a reference to Phoenician ships sent by Darius (c.550-486 BCE)) to Greece to undertake a reconnaissance mission during which, according to Herodotus, they were to compile “a written record of the results of a careful study of the most notable features of the coast”. 261 

We are left with a number of questions about the relevance of possible alternative, or complementary, sources for the coastal itinerary statements in the portolani:

G.1d. Settling the priority question

The realisation that the details in the Liber’s pelagic statements must have been obtained from a prototype chart of some kind was a major discovery. 264  Each of the single directions, followed by a mileage figure – neither of which would have reflected the realities of a long voyage – could have been obtained only by reading the bearing off the wind compass network of a marine chart and scaling the distance from the same source. But that on its own does not wholly answer the ‘chicken and egg’ question about the primacy of text or chart. Even more convincing is the parallel evidence from the portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes’s coastal itineraries.

It would have been easy to list the sequence of places along a coast. Additionally, in some cases, neighbouring ports would even have been visible, so that recording the direction and distance from one to the next would have been straightforward. But citing the bearing and mileage between successive places along an irregular shoreline, perhaps formed out of a series of bays and promontories, would have been a different matter. What sense could be made of a single bearing if, in order to get from that place to the next, the helmsman had first to steer a course that would take him safely out of port, then put out to sea for a while, having next to turn in order to round a headland, and finally change course once more to enter the new harbour?

In the same way, a mileage figure could have been readily provided, but what would it have meant in those circumstances? Was it merely a measured straight line, relevant only as a cartographic abstraction? Or did it attempt to convey the amount of time actually required. This point is more than a trivial one. Before any effective test could be carried out as to the accuracy of the coastal distances stated in the portolani, the method used to obtain the sequence of distances and how they were intended to be interpreted would first have to be resolved. The toponyms on the portolan charts were not carefully positioned anyway, so an equivalent exercise could not be carried out there.

The debate as to the priority of the portolani or the portolan chart is clearly in favour of the latter. Joaquim Alves Gaspar’s assertion, quoted above, 265 is fully vindicated. The stated directions in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) and Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) must have been straight lines calculated by eye from a chart’s network of compass lines [Powerpoint, Slide 15], and the distances would have been measured with a ruler. In other words, not only must a marine chart have preceded the oldest portolano that included direction and distance statements, but, since the chart was the source for those, it must have partially enabled the development of such texts.


Table of Contents


For brief summaries see the Conclusions


 

PART 2

THE CHART EMERGES

 


 

Introduction

Having explored at some length the various aspects of the environment out of which the portolan chart seems to have emerged – probably somewhere around the year 1200 – it is time to turn to the charts themselves. The best available evidence is of course the earliest survivor, the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118>.

For uncountable centuries before the advent of the portolan chart, sailors must have gone through a similar, but very personal, never-ending learning process during which they constructed an approximate picture of the Mediterranean as a whole, and the specific placement of its many islands within that. No pelagic sailor who had responsibility for navigation could have done otherwise. And no landsman – at least judging by the maps that survive from before 1200 – could have had access to outlines remotely equivalent to those memorised by pilots. Compiled in very different ways, al-Idrīsī’s Charta Rogeriana 266 and the maps based on Ptolemy’s Geographia demonstrate the constraints facing those viewing from the land when trying to plot the circumference of that sea (or, to put it another way, the continents’ landward limits).

It seems that the overall mental map of the Mediterranean, which this essay identifies as the sole geometric source for the portolan chart, was effectively, if unintentionally, a trade secret, commonplace (if incomplete) for open-sea sailors but beyond the reach of those not directly involved in navigation. Each mental map must have been unique, comprising a dossier, made up, first, of oral knowledge and, second, personal experience. It would have been built up over time, and used in much the same way as a goldsmith or a boat-builder would have regularly consulted his memory rather than a text. Such knowledge represented a pilot’s personal capital, much of which would still have been required even after the portolan chart became available.

But, until those pelagic details had been set down graphically – after mental maps had been shared, in order for the discrepancies to be ironed out – nobody could possibly have had the full realistic overview, as displayed, for example, on the Carte Pisane, which, for the most part, is fully recognisable today when placed alongside a satellite image. Unlike us, who take for granted that the pictures we see from space are unquestionably true, the medieval sailor and land-based merchant alike, had to depend for reassurance on the experience of those who must have described, for instance, how they had found a particular feature where the chart said it would be. No other verification method would have been possible until the scientific hydrographic surveys of later centuries. Contrast that with what would have happened if the Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text or Ptolemaic maps had been used as a sailing guide.

One of the challenges facing a cartographic historian is to see the world through the eyes of the past. For us, the question ‘what does the Mediterranean really look like’ is redundant. We start with a single possible answer, particularly after our planet was photographed from space. It is almost impossible for older people to forget that image, and remember how previously we had to rely on maps taken on trust. But how would a savant in 1200 have been able to adjudicate between, say, Ptolemy’s maps (had they been available), the mappaemundi’World maps’ in Latin (singular, mappamundi). Used to distinguish medieval maps of the world from those of Ptolemy and the portolan charts or the Islamic depictions? Which was better? Which was ‘right’? 267  The navigator, on the other hand, with his systematically gathered and carefully stored memories, regularly reinforced by further voyages, was in the unique position of being able to answer those questions with confidence. Not, of course, because he had ‘seen’ the Mediterranean in its entirety but because he had mapped out or learned much of it, piece by piece, and stored the results in his head.

It is also worth asking the further fundamental question: why would anybody not directly involved in maritime trade (whether carrying goods or passengers, as a navigator or a merchant) have had any need for a precise overall map? What moral, theoretical, doctrinal, even geographical questions, would it have resolved? The responsibility for mapping coastlines was shared between hydrographers and land surveyors, working in opposite directions, but only for the former was geometric accuracy a necessity. This is what makes the portolan chart, the oldest marine chart of which we have certain knowledge, an unprecedented development, matching a highly ingenious format to sailors’ spatial needs.

Leaving aside the now discredited notion that most medieval voyages kept close to shore 267a – where, ironically, more of the dangers threatening a ship are to be found – it is transits made out of sight of land, the ‘pelagic courses’, that are the main concern of this essay. The Mediterranean is not a single open ocean but instead made up of separate seas. These are dotted with a wide assortment of islands, large and small, isolated or clustered into archipelagos. Though some of those certainly threatened shipwreck, they also allowed a long-distance course to be broken down into manageable segments, while simultaneously offering food and water [clearly an even bigger consideration when carrying pilgrims or other passengers, compared to undemanding cargoes]. Crucially, as is argued here, the islands would have provided much of the underpinning for the portolan charts’ geometric structure.

Knowledge of those pelagic courses would have come, variously, from retained oral instructions or the carefully observed and remembered details of past voyages. Along with the navigational instructions resolved upon before leaving harbour, this would mean that the pilot set out well prepared to follow a specific bearing (or a sequence of those if the course was divided into several legs), insofar as the winds would allow. How such tracks could have been joined up, first, into a mental diagram and then as the basis of a marine chart, will be discussed later.


Table of Contents


For brief summaries see the Conclusions


 

H. INDICATIONS ABOUT THE DATE AND PLACE OF ORIGIN

 


 

H.1.  POINTERS TO THE LIKELY PERIOD OF THE PORTOLAN CHARTS’ CREATION

In attempting to narrow down the most likely period for the appearance of the hypothetical prototype of a portolan chart we can call upon a number of types of ‘evidence’, or, more realistically, ‘circumstantial indications’.

It is necessary to consider first the claim that is occasionally made of a supposed reference to a marine chart a century earlier than any other. There is a mention in the Alexiad by the Byzantine princess Anna Comnena (written about 1148) that, her father, Emperor Alexis I, had drawn a marine chart in 1107 or 1108. However this does not point to an early date for the portolan chart. Indeed, since the map (“of the coast of Lombardy and of Illyria, putting in the harbours on either side”), concerned a potential crossing of the Adriatic from ‘Lombardy’ to Durrës (Albania) it is better interpreted as a freshly-drawn sketch map, no doubt based on sailors’ knowledge. There is no suggestion that a chart of the Mediterranean was involved. Indeed, if the Emperor had access to a portolan chart he would not have needed to create his own map. 268 

H.1a. The confirmed terminus ante quem

If we begin at the end, seeking to establish when a marine chart was certainly in existence, the first clear reference starts with the chronicler Guillaume de Nangis’s account of an incident on Louis IX's voyage of 1270 when, after four days of violent storm, a document of some kind (decribed as a mappa mundi but it is hard to see what it could have been other than a marine chart) was produced to help determine the fleet’s position. Ten years later, in 1279, Egidio Colonna (Giles of Rome), in his De Regimine Principum, referred to the value of a chart for denoting nautical dangers, thereby demonstrating its established status. 269  The next consideration might be the ambiguous evidence concerning the dating of the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . Despite a controversial re-dating to the later 14th or even 15th century by Ramon Pujades in 2012, 270  I argued, in an extended online essay of 2015, 271 that the Carte Pisane should be confirmed, on various grounds, as being clearly the oldest survivor. I proposed a likely date of around 1290. Then, in 2016, the Carte Pisane's vellum was submitted to Carbon-14 testing, which gave a possible date between 1170 and 1270, with 95% certainty. Such analysis gives equal weight to each one of the hundred years involved, so, on the basis of that finding, the Carte Pisane could have been drawn as late as 1270 or, because it was the substrate (the vellum) that was tested rather than the map itself, perhaps even a little later. It is reasonable therefore to return the Carte Pisane to the latter 13th-century period it had previously occupied, perhaps 1270. Or even conceivably a little earlier than that. 272 However, the Carte Pisane does not look like a prototype and the next section describes a series of logical steps that place a usable marine chart some decades earlier than 1270.


Table of Contents


For brief summaries see the Conclusions


 

H.2a. The Liber’s Black Sea toponyms

The triangular investigation that follows involves a single text, the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v), the lost forerunner of the portolan chart of the Mediterranean, and a hypothetical extension of that into the Black Sea. All the textual evidence is concentrated into just one of the 47 sections in the Liber. The argument that follows may appear tortuous in places, but it cannot be avoided if this central aspect of the portolan-chart origin story is to be unscrambled. The Liber’s Black Sea information may be our best guide to the likely date of that work itself. Simultaneously, it can be used to help define the portolan chart’s terminus ante quem. If the dating of one changes, so does the other.

The Liber’s listing of the mileages between pairs of distant Mediterranean termini, is now understood as pointing to measurements taken from a marine chart. 273  However, the section of its text that describes the Black Sea is handled differently. This raises related questions: was that passage part of the original work or a later addition; would the Mediterranean chart have already extended eastwards to embrace the Black Sea; or did that information stem from one or more non-cartographic sources?

The limited textual evidence will be examined first, in an attempt to understand the significance of the scattered toponyms. The likely sources will then be considered, including a possible eastwards extension to the marine chart of the Mediterranean. Finally, the focus turns to the dating of three closely interrelated elements: the Liber, the Mediterranean chart (and, hence, the portolan chart in general), and the topicality of the information provided about the Black Sea.

Out of the Liber’s total of 2,356 lines, the relevant section covers no more than 55 of those, with the entire Black Sea toponymy squeezed into less than half that number. 274  Furthermore, the details offered in the Liber are fragmentary. However, despite the absence of any mention in the work’s Prologue that the Black Sea was to be included, 275 that section (16th out of 47) shows no sign of being a later addition. That contrasts with the equivalent portion of Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396), which was placed at the end of the volume, as an acknowledged supplement.

In the first place, the toponymy is very limited. When compared to Lo compasso (c.1260-96), which has 104 Black Sea toponyms, the Liber musters only 13. These are listed below, following the Liber’s counter-clockwise sequence. The number preceding each entry indicates the respective line in the Liber, whereas the terminal number refers to the present author’s comprehensive Excel listing of portolan chart toponyms. 276  That includes, inter alia, all the mainland names in both the Liber and Lo compasso, thus providing a sense of the wider context.

983: ins. phynosia (Finoxia) – 1312
984. eraclea (Penderarchia = Eregli) – 1306
985. caput samastri (Amasra) – 1297
986. caput cithero (Kytoros, Gideros,or Kidros) – 1293
987: tribisonda (Trabzon) – 1254
988: matric (Matrega) – 1204
993: comania (?) – 1175 [this appears to refer to the local people, but the toponym is regularly noted elsewhere]
996: soldadia (Sudak) – 1157
998: cersona (Sevastopol) – 1146 (‘where Ovid was exiled’)
1003: costancia (Costanza) – 1097
1004: castrum vernia (Varna) – 1089
1005: mimsenbro (Mesembria) – 1082
1006: oscelon (?) – 1077b
[various numbers]: ostano (Ostanum, at the entrance to the Bosphorus), on which see below. 277 

As confirmed by the terminal numbers above, the Liber’s list is in the correct coastal sequence (as shown in the Excel spreadsheet), implying a degree of geographical knowledge. However, comparing the gaps between consecutive numbers highlights their uneven distribution. Essentially those 13 toponyms break down into three groups and one isolated name. Heading east from the sea’s entrance at the Bosphorus, the first group comprises four toponyms clustered around Amasra; then a single name, tribisonda (Trabzon), representing the remainder of the south and the east coast; next Matrega (close to the Kerch Strait) along with a pair of names in nearby Crimea; and finally four ranged south along the Bulgarian coast from the Danube estuary, heading back towards the Bosphorus once more. The possible explanation for this apparently random distribution of toponyms around the Black Sea, and the reason that those names were chosen rather than others, will be considered later.

Referred to no less than eight times, ostano (Ostanum) features near the beginning, and again at the end, of the sea’s circular toponymic sequence [lines 981 & 1007]. Although this ‘locus’ [lines 647-8] has not been reliably identified, 278 it was presumably a port situated close to the mouth of the Bosphorus. 279  Indeed it may be the ost… that was partially legible just to the north of Constantinople at the time the facsimile was made of the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) in 1852. ostano, standing in for the entrance to the Bosphorus, is individually linked to the first name along the south coast (phinosia) and the first- and last-named places on the west coast (oscelon and costanza).

Two of those toponyms seem not to have been recorded in any other chart or portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes: cape cithero (although the town was known) and oscelon. 280  Of the remainder, almost all are found in Lo compasso and again on the first dated chart, (by Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated in 1311) where they are coloured red to denote significance. In other words, they were among those names likely to have been chosen if a selection of notable places was being made.

Today, ‘Bosphorus’ means just one thing: the strait that divides Istanbul and the Sea of Marmara from the Black Sea. In the Liber, though, following contemporary usage, the word is applied also to the Kerch Strait (formerly Cimmerian Bosporus), leading from the Black Sea into the Sea of Azov. Of the nine instances of the term ’Bosphorus’ picked up in Patrick Gautier Dalché’s indispensable index, nearly all refer to that north-eastern instance. 281 

H.2b. Black Sea distances

Most of the mileage figures are missing from the Liber’s Black Sea statements but the space for them was indicated. From that it seems fair to assume that the author intended to return to fill them in, either from information he already held or that he anticipated receiving. 282  Those omissions are frustrating because the mileages would have allowed the quality of that geographical information to be tested.

Viewed in that light, it is significant that there was also an intention to include the Black Sea’s overall dimensions in the introduction to that section, and likewise those of the Sea of Azov (meotide paludes) [line 964]. Estimates of the Black Sea’s extent could have been obtained from Classical sources, for instance Ptolemy’s Geographia, but there is no evidence of the circulation of that work in the Latin world of 1200. Kiril Nenov, whose focus was on the geographic and toponymic aspects, proposes that the Liber’s author wanted to demonstrate his command of both Classical and recent geographical authorities, as evidenced for instance by the alternative names he supplies for the Black Sea and its two straits. 283  Among the paired coastal places described, several were far apart; however, what must have been open-sea tracks are disguised here through the omission of the bearings habitually provided by the Liber for the Mediterranean instances, in conjunction with mileage figures. A direct voyage between tribisonda (Trabzon) and Matrega [lines 987-9], for example, would have covered around 500 km, and cersona (Savastopol) to the Danube estuary [998-1000] in the region of 420 km. As a contrast to those, there are the usual, much shorter, coastal hops noted between neighbouring places.

H.2c. How likely is it that the Black Sea information was taken from a marine chart?

There seem to be three alternative (or combined) sources for the information in the Liber’s Black Sea section: a marine chart, a pre-existing geographical account, or orally-conveyed information. A marine chart might seem the obvious candidate because it has recently been established by Joaquim Alves Gaspar that the Liber’s author, as far as the rest of his text was concerned, would have copied the direction and distance information from a marine chart of some kind. 284  It is not unreasonable to consider applying that precedent to the Black Sea as well, because of the evident maritime bias in the choice of the toponyms. Two of them are capes (samastri and cithero), vital for pilots, two denote islands (finoxia, now Kefken), which sits off a third headland, while the name cersona was applied to both a town and an island. In this respect, the statement that 3 ml. separated soldadia from its harbour is a significant detail. Furthermore, nearly all the other toponyms can be found in the mid-13th century pilot guide, Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396), and on the early portolan charts, thus confirming their relevance for navigation.

It is also possible that mariners could have built up a mental picture of the interrelationships of the Black Sea’s prominent trading centres, comparable to that which is being proposed in this essay for the Mediterranean. But the Black Sea had a turbulent history, which makes it less likely that such knowledge – if it even existed – would have been inherited and shared in the way that must have occurred in the Mediterranean. Successive rulers in Constantinople controlled access via the Bosphorus, barring entry to the ships of rivals, while sections of the coastline were under the control of shifting regional powers.

Moreover, there is no justification for assuming that those maritime details would have come from a cartographic document, let alone that the Liber’s author would have been reading off his distances for the Black Sea from a precursor portolan chart in the way he had evidently done for the Mediterranean. If he had had access to a marine chart, even a rudimentary one, it would presumably have had broadly complete outlines, and have been defined by the placement of at least a representative selection of toponyms. Although our approach and interpretations are different, I concur with Nenov’s judgement that “The author of the Pisan geography tried to make as thorough description of the Black Sea region as the data he disposed of would allow him to”. The Prologue acknowledges the author’s “ignorance or imperfect memory" 285 but nothing we know of his stated purpose suggests that he would have intentionally omitted relevant information. As examples of Classical texts that must have been unknown to the Liber’s author, Benet Salway refers to the Roman Governor Arrian’s ‘Circumnavigation of the Black Sea’ (130s CE) and the Dura parchment (mid-3rd century CE), reproducing their littoral toponymies. 286 

Classical geographers could have been responsible for the error of a north-south trending Sea of Azov (instead of north-east then turning to the south) but such a source would have included many names. If the author was aware of toponyms left unused, such as Tana[is], that might indicate his wish to avoid including obsolete information. As will be shown, those of his toponyms that can be reliably identified had current relevance.

On balance, therefore, it seems more likely that he depended for his Black Sea information on what he had learnt in discussion with pilots (perhaps his former shipmates). For example, the toponyms that he does note could have reflected the personal experience of one or more sailors. The details of each short sequence might have been gathered by a single individual, based in just one port, from where he could have learnt about neighbouring places. Likewise the promised mileage figures, such as that for the long pelagic crossing from Trabzon to Matrega, rather than being measured off a marine chart, could have come from somebody who, having done that particular voyage, translated the duration into miles. 287 

That scenario would make sense only in the absence of an existing marine chart, focused on or including the Black Sea.

H.2d. Establishing a terminus ante quem for the portolan chart

The crucial development, which helps explain the various anomalies described above, was the sack of Constantinople in 1204 and the opening up of the only route into the Black Sea, via the Bosphorus. 287a  This would have been ‘stop press’ news and merchants, predominantly Venetian, must have lost no time in taking advantage of this lucrative access to trade goods from the East.

Unless there are dating clues hiding in the Liber’s scattered toponyms, none seems to indicate an event later than 1206. The main developments after 1204 would have been mercantile ones and each of the toponym groups includes a well-established trading centre. One of them contains soldadia (Sudak) in Crimea, a Silk Road terminal, settled by Venetian merchants as early as 1206. The isolated name, Trabzon, was another Silk Road port, the centre of the eponymous Empire of Trebisond, into which both Sevastopol (Crimea) and Amasra (in the south-west group) – formerly under Byzantine rule – were incorporated at the foundation of the Empire in 1204.

Whereas the geographical details presented by the Liber were mostly historical, the toponymy and sailing routes were apparently up to date, and the strong contemporary mercantile and nautical flavour of the names points to mariners as the informants. There is no readily available evidence about further mercantile developments in that decade which the Liber’s author might have been expected to register (because of their direct relevance for trading vessels). Since both the limited and dispersed toponymy, as well as the pelagic tracks, fit in with the early stage of post-1204 development, it seems reasonable to suggest that the Black Sea section was being composed not long after 1204, and at the outside, perhaps 1210. 288 

In relation to dating the appearance of the first marine chart, this investigation has shown that it is highly unlikely that an extension to the Mediterranean outlines or any kind of independent survey of the Black Sea was available to the Liber’s author. From that it would follow that the marine chart in circulation prior to 1204, would have been solely focused on the Mediterranean, with its eastern terminus at Constantinople. Likewise, at the western end, the Carte Pisane’s pre-cartographic representation of the Atlantic coasts indicates that the earliest charts are likely to have started at the entrance to the Mediterranean, and have been exclusively concerned with that.

[This section has dealt with aspects of the opening up of the Black Sea after 1204 and the implications for dating both the Liber and the portolan charts. See J.1. ‘The charting of the Black Sea’ for a tentative account of the process whereby its coastal outlines and toponymy were documented later in that century.]

H.2e. The Charta Rogeriana establishes the portolan chart’s terminus post quem

Considering instead the other end of the dating envelope for the portolan chart, the terminus post quem – a time when it was not in existence – the focus shifts away from the Black Sea to the Islamic world. The absence in Muhammad al-Idrīsī’s very large world map (the Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text ) of any trace of the portolan charts’ unique outlines and characteristic conventions provides near certainty that no marine chart was yet in circulation at the time it was completed (in or shortly after 1154). The justification for that statement (based, on what would normally be shunned, namely negative evidence) relates to al-Idrīsī’s exhaustive fifteen-year geographical survey. Master-minded from Sicily with its pivotal location at the centre of the Mediterranean – both physically and with respect to its mixture of learning from different cultural traditions – that exercise involved numerous interviews with travellers and sailors. As a result, al-Idrīsī could not have failed to take note of the realistic coastlines of a marine chart if one had existed. When mariners visited Palermo, and were questioned by al-Idrīsī, they would undoubtedly have endorsed the accuracy of any chart they had in their possession. 289 

It is the contention of this essay that the portolan chart did not develop over a long period but must have arrived in the form of a recognisable geometric network for the entire Mediterranean. Hence it would not have made sense for al-Idrīsī to have borrowed selective elements, had he seen a chart. What he might have done, as the 14th-century authors of mappaemundi’World maps’ in Latin (singular, mappamundi). Used to distinguish medieval maps of the world from those of Ptolemy and the portolan charts did, was to use a portolan chart for the Mediterranean (including the signature feature of the Gulf of Sirte), turning to other sources for what lay beyond to the east. The Catalan AtlasActually a sequence of six panels, two of which cover the area of the usual portolan chart and two others extend east to make this a world chart, c.1375 (Paris, Bibliothèque nationale de France, Manuscrits, MS. Esp. 30) is the earliest instance of that, though that is unsurprising since its author was a portolan-chartmaker.

It is unusual, when trying to pinpoint a medieval development, to be able to relate that to a known event. For there to be two attested dates defining a window of possibility is exceptional. In the case of the portolan chart, if the pieces of the jigsaw have been correctly assembled, the period concerned can now be narrowed to a conveniently neat 50-year range, 1154-1204, replacing previous estimates that had spread over centuries.

H.2f. Palaeomagnetism

Since magnetic minerals in rocks provide a record of the direction of the magnetic field at the period they formed, the growing body of palaeomagnetic data may have evidential value for the question of portolan chart origin. The long understood tilt of the Mediterranean axis displayed on the charts is assumed to represent the magnetic declination at the time of their creation. On the basis of data gathered by Korte & Constable (2005). 290  Joaquim Alves Gaspar has pointed out that “the comparison between the average tilt of the Mediterranean axis in the charts and the variation of the magnetic declination in the area, from 1200 to 1600, suggests that the first prototypes were probably developed between 1200 and 1250”. 291  The difference between those two dates is of considerable importance for the origin argument and further refinement of the palaeomagnetic data is awaited with interest.

However, as discussed in a previous section, 292 the relevance of this evidence depends on whether or not the magnetic compass played a direct part in the origin of the portolan chart, rather than – as is argued here – it being more likely that the chart preceded the magnetic compass.


Table of Contents


For brief summaries see the Conclusions


 

H.3.   WHERE MIGHT THE PORTOLAN CHART HAVE ORIGINATED?

Among the litany of fundamental questions facing anybody seeking to unravel the long-standing mystery about portolan chart origin – who, when, where, why, and how – the ‘where’ has been ignored in this essay until now. This is not due to negligence but rather from a lack of convincing evidence.

Leaving aside the long-abandoned nationalistic claims for Italian or Catalan primacy, it is now generally accepted that the portolan chart was probably born in one of the ports along Italy’s west coast. Genoa and Pisa are most frequently suggested, on the grounds of their maritime power. Those are the most obvious candidates but is there real evidence in favour of either?

The most promising pointers to the charts' port of origin (albeit indirect ones) may be found in that disparate group of six anonymous charts that followed the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) [to be discussed later under N.1b. ‘Not a single lineage’.] As will be argued there, those were probably produced in different locations in the first decades after 1270. Certainly some of that group can be treated as Genoese, and Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his atlases and charts survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest signed and dated charts seems to have had a monopoly in Venice. So, where might the Carte Pisane, Cortona chartBased on its archaic appearance, this is considered to be the second oldest surviving portolan chart after the Carte Pisane, dating from the beginning of the 14th century or even earlier. It was first described in 1957 (Biblioteca dell'Accademia Etrusca di Cortona, Port. 105), Avignon chartA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html and Lucca chartDiscovered in 2000 in the city archives, this is visually very different from other charts from the 1st quarter of the 14th century (Archivio di Stato, Lucca, Fragmenta Codicum, Sala 40, Cornice 194/1) have originated? Evidently neither Genoa nor Venice. If it is accepted that the earliest surviving charts were being produced in different ports (perhaps minor ones), there is no justification for the assumption that the birthplace, some decades earlier than 1270, must have been one of the major centres. It makes better sense to leave all options open about the ‘where’ issue until some solid evidence emerges.

Considering the question of the Carte Pisane’s place of production, Ramon Pujades favoured somewhere in the Kingdom of Naples, perhaps Gaeta, although that was in the context of an argument that relegated the Carte Pisane to a date no earlier than the late 14th century. 293  However, even now that it has been restored to its former position as the oldest survivor, the Carte Pisane is likely to have been preceded by over half a century of prior development. Thus, there is no reason to suppose, even if the Italian port out of which the Carte Pisane emerged could be identified, that this would have relevance for the location from which the first chart emanated. 294 

Perhaps the whole ‘where’ discussion is misplaced. On the basis of the claim that the portolan chart was not born in a cathedral precinct or a scholar’s study but in a quayside tavern – and likely through the collaboration of pilots from different regions – the hunt for a specific location for the urchart may be a chimaera.


Table of Contents


For brief summaries see the Conclusions


 

I. FIRST THE PELAGIC DIAGRAM AND THEN THE CHART

 


 

I.1.  ‘INADVERTENT TRIANGULATION’

From the time a young sailor made his first voyage he must have begun to commit each separate course to memory. The big conceptual leap would have come when a mariner’s memory store moved from retaining just a single course, or a number of unrelated ones, to building up the beginnings of a coordinated picture. With this would surely have come the realisation that the inter-connecting courses, and particularly those converging at a particular terminus, created a network of triangles, even if they would not have conceived of those in Pythagorean terms [Powerpoint, Slide 16 – an analogous diagram of the Pigeon Post in Moscow, 1941].

By moving from a simple linear view to a multi-linear network, an experienced sailor would have started to visualise the pelagic courses in the form of a simplified proto-cartographic diagram. As Joaquim Alves Gaspar has commented:

When trying to assess the accuracy of the information about pelagic tracks (that is, of courses and distances) we should take into account the fact that some of those tracks had been practised for a very long time (hundreds of years, in some cases). This long experience must have been reflected in the quality of the information. This may explain why the longest non-magnetic pelagic tracks listed in the Liber are exact (in a 16-winds rose), for example, Massilia to Bugea or Patera to Alexandria. In other words, we should not mistake the accuracy of a specific transit with the accuracy obtained on the basis of many. 295 

Triangulation is a classical technique lost to the West before the later Middle Ages (and hence an anachronism in this context), which is why the alternative term ‘inadvertent triangulation’ has been suggested. There may, perhaps, be a useful analogy in the experience of Molière’s ‘Monsieur Jourdain’ when he suddenly realised that “these forty years now I’ve been speaking in prose without knowing it!”

In the context of his theory about the sub-basins, David Woodward put a comparable view of the likely process involved, even if our explanations differ:

It must be stressed, however, that this theory does not require that modern methods or instruments of trilateration or triangulation be available in the thirteenth century. Indeed, there is no evidence that such techniques were available until the fifteenth century. The terms are simply used as an analogy for the natural structure that may have underlain the charts. 296 

How might that ‘inadvertent triangulation’ have come about? 297  For navigation purposes, it was often islands that were of the greatest use, for example if an island came into view when still within sight of the disappearing land. Such intervisibility would double the number of reference points available to the observer, while simultaneously confirming the direction and distance between a pair of landmarks. Thus the positions of intervisible features could have provided a solid basis for any diagram that had been built up by working out from the shore.

For instance, in some parts of the Tyrrhenian Sea (probably close to where the portolan chart was born) the navigator would have had a view of sections of the Italian coastline and, at the same time, been able to see one or more of the islands, particularly Corsica and Sardinia. Even without a formal understanding of Euclidian geometry, the properties of the ensuing triangles could have been worked out intuitively.

It would have been habitual for mariners to have noted the bearing and direction between intervisible points and subsequently checked that information for accuracy when sailing the return course. For example, take two sightlines, AB and AC, from a hypothetical position A. Those would have created a clear angle at A, and if the navigator drew those two lines out according to observed direction and estimated (or remembered) distance, that would have enabled him to connect the termini of those lines by drawing in line BC. The scale, whether it was an internal one or ruled off from a measured scale bar, would then have allowed him to estimate the length of BC. In the process, a triangle would have been accidentally created. No formal mathematical knowledge, as we understand it, would have been involved. However, if the toleta de marteloio‘A trigonometric reduction table to aid navigation by dead reckoning’, used to calculate the actual course sailed when tacking into the wind was indeed used at sea, the fundamental principles described above must presumably have been involved in its operation.

Such a hypothetical ‘triangulation’ could have found corroboration when overlapping sightings were added later. Depending on how widely such a process extended, it could, in principle, have resulted in a recognisable chart covering much of the grey zones on Joaquim Alves Gaspar’s diagram, 298 where land would be visible for sailors. There is no clear evidence that something like that happened, but the archival silence applies equally to the conjectures about a running survey of the entire Mediterranean and Black sea coastlines, or that the eventual portolan chart was the product of joined-up surveys of the separate basins. 299 

However extensive the ‘grey area’ triangulation might have been, that alone would have remained partial and without any overall coherence. There would still have been no means, for example, to link the eastern half of the North African coast to the European islands to the north, while relating the opposing sides of the Black Sea would have been equally challenging. The stitching together of the grey zones could only have come about by incorporating the pelagic tracks across the landless sectors, Gaspar’s black zones.


Table of Contents


For brief summaries see the Conclusions


 

I.2.   THE MENTAL CHART TAKES GRAPHIC FORM

It was at one time suggested (in an earlier draft of this essay) that a single word in the Prologue of the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) might have been interpreted as a reference to a graphic diagram containing pelagic courses. If so, it could have supplied direct evidence for the origin of the portolan chart. This claim (now abandoned in the light of a new translation) is here briefly summarised for the record.

I.2a. gradiens

The main matter of the Liber is preceded by a ‘Prologue’, spread over two sides of a single leaf. 300  The transcription and translation of that text has proved challenging. Here we focus on a short passage, and indeed on a single word gradients. Because this is the only statement the unidentified author makes about the sources of his information, it is of obvious importance.

The Latin text reads: Ubi longitudo et latitudo et angustum eorum inter utrasque partes riueriarum Libie et Europe, iuxta quod a nautis et gradientibus illorum… [Powerpoint, Slide 17]. The translation which Joaquim Alves Gaspar commissioned from a group of Latinists for his 2019 Imago Mundi article is as follows: “As for the length and breadth and narrowness between one and the other parts of the coastlines of Africa and Europe, I have shown [them] in accordance with what I have been able to know and discover from mariners and travellers of those [places]…”. 301  Much hangs on the translation, within its context, of gradientibus. For that word, Patrick Gautier Dalché had tentatively offered as translation guides nautiques, although it seemed strange that an unknown term would have been applied to a work similar to the Liber itself. My own delving had found various cited meanings for the singular form gradiens, such as ‘port’, ‘position’, ‘degree’, ‘travelling’, and words expressing forward motion. That had seemed to offer the possibility that this unusual word might have referred to the diagram of pelagic courses that is being proposed in this essay. 302 

As a non-Latinist I must defer to those scholars named at the end of Gaspar’s article. However, it is appropriate to observe that, if the only sources cited by the Liber’s author are ‘mariners and travellers’, we might wonder what that second group (the gradientes) could usefully have added. They could certainly not have provided the navigational information and, in particular, the Liber’s pelagic data – though those details were probably measured from a cartographic image anyway. 303  Furthermore, it is highly unlikely that such ‘travellers’ would have contributed usefully to the coastal itinerary either. Why would passengers have observed and noted the direction in which they were sailing between ports, or have been sufficiently concerned with the mileage to have recorded that? They would have remembered, perhaps, the sequence of places, their name, appearance, any peculiarities, or their own experiences, but probably little else. Even on the assumption that gradientibus has been satisfactorily translated, its meaning in that context remains obscure.


Table of Contents


For brief summaries see the Conclusions


 

I.3.   WHAT MIGHT SUCH A PELAGIC DIAGRAM HAVE LOOKED LIKE?

Assertions:
The charts’ geometry could plausibly have come from one source only: pelagic courses memorised by pilots.

The numerous courses sailed by an experienced navigator would probably have been memorised as an interconnected network, instead of or in addition to being stored in the brain as separate routes.

It is hard to visualise how a very early, rough, ‘amateur’ outline of the Mediterranean could have been of any practical use for mariners. However, the putative geometric diagram, by recording the embarkation, destination and intermediary points of pelagic voyages, would also (perhaps accidentally) have defined the sea’s outer limits.

The visual appearance of such a hypothetical diagram is open to conjecture. Perhaps it would have been a network of straight lines (perhaps, for the longer courses, in the form of dog-legs). The reference points might have been named or provided with just an initial. If so would that undermine the illiteracy argument? 304  Or would writing have been unnecessary if, as is contended here, such a diagram mirrored what was in the sailor’s head anyway so that he would have readily identified a place in relation to what was around it? For the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v)’s author to be able to cite distances from all around the Mediterranean, at least the rudimentary outlines of the portolan chart we recognise today must have been completed. Inevitably, few of the longer open-sea measurements mentioned in the Liber involve the Adriatic or Aegean seas. 305  But that should not surprise us since sailing in those waters was never out of sight of land and such pelagic information was therefore not needed. Indeed, it is perfectly possible that the first attempt at an overall chart of the Mediterranean omitted those two seas altogether.

I.3a. The sailors’ viewpoint

It is worth going back to basics and asking the question: how might a medieval mariner have envisaged the Mediterranean? The sailors’ viewpoint is both horizontal (across the waves) and vertical (when examining in profile an island they were passing or the coastline appearing over the horizon). By contrast, a portolan chart is, in effect, the coastal outline extracted from an aerial view: in other words what we take for granted in a planimetric map. The charts of Lucas Jansz. Waghenaer, in his printed Spieghel der Zeevaerdt (1584) combined two of those viewpoints, with rough profiles of cliffs placed beside the coastal outline.

For a traveller on land, the roads and rivers provide a horizontal network that can be readily imagined as a map, but there was no equivalent aid for a sailor. How would the charts’ creators have been able to translate what they were seeing into cartographic form, particularly, as is suggested elsewhere, if they might never have seen a map of any kind before? 306 

The way that the putative mariner(s) who devised the portolan chart (probably at the end of the 12th century) arrived at that aerial view, extrapolated from the profiles they had observed, is one of their major achievements. Even in the 15th century, as Matthew Boyd Goldie pointed out: “An unlimited and an overhead aerial perspective and understanding of space was possible for people at this time, but it was not how people customarily thought about or presented the areas around them”. 307 

I.3b. The charts’ projection?

Underlying this essay is the thesis that portolan charts owe their structure to the memorised pelagic courses, which had placed the features of navigational significance in the Mediterranean and Black seas in realistic relationship to one another. From that, it follows that the charts are projectionless, as others have previously suggested. 308  What intermediate mathematical calculations could have intervened between mariners’ memories and the graphic record of those? 309 

Joaquim Alves Gaspar elaborates further on the portolan charts’ lack of a formal projection:

Specifically, it made it possible to demonstrate that the main geometric features of portolan charts are explained by assuming that the navigational data—compass courses and estimated distances—used in their construction were transferred directly onto the plane of the chart irrespective of the fact that the measurements had originally been made on the earth’s spherical surface. While no medieval text confirms this hypothesis, early modern texts explicitly refer to charts of the Mediterranean being constructed by using compass courses and estimated distances collected by pilots. 310 

On the question of the portolan charts’ projection, or lack of one, Roel Nicolai’s is a dissenting voice. The issue is much discussed in his 2014 thesis and was summed up thus at the end:

The map projection found in portolan charts cannot be the unintentional result of a simple chart construction method or an accidental by-product of any cartometric analysis process. The follow-on conclusion is therefore that, in the absence of any convincing alternative explanation, the map projection is not accidental, but must have been intentionally designed into the charts as part of their construction. 311 

That needs to be considered alongside another statement by Nicolai that: “The construction of a chart with an a priori intended map projection would definitely be well beyond the capabilities of medieval sailors, cartographers and even the intellectual elite of that period”. 312  Nicolai’s repudiation of the possibility of a medieval origin for the portolan charts has been challenged throughout this essay.

I.3c. The missing link

This brings us close to the crux of the portolan chart enigma: the missing link between, on the one hand, an imagined prehistory containing a number of logical but largely uncorroborated developmental phases and, on the other, by the oldest surviving example of the genre, as well as two texts, each unique, each of uncertain dating, and each open to differing interpretations. Additionally, the novelty visible in a series of extraordinary conceptual leaps, which might have involved more than one person at more than one time, and the total absence of the expected ties to a previous cartographic tradition, means the range of options is a large one.

Here I immediately diverge from some other commentators. Whereas it is argued here that pelagic memory was the ultimate source, Ramon Pujades (and others) argue that the charts had a textual paternity. In his contention he refers to “data transposed from the written to the graphic format, which constituted a genuine revolution from the intellectual viewpoint”, which he refers to elsewhere as “the major exercise in mental abstraction involved in the transposition of a written compilation of data on distance and direction to the graphic format of a scale map endowed with a wind network”. 313 

Pujades makes a specific conjecture that it was the clergy who played this crucial linking role, since as a sector they were “directly involved in the task of compiling and organising information which, amassed by sailors from their experiences at sea, would initially have been restricted to the oral realm”. He goes on to suggest that “in all probability, the author of the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) was one of the numerous clerics who acted as notaries and chaplains on the naval convoys”, and he finally makes a specific proposal that “the first navigational chart makers would have belonged to this same socio-professional group.” 314 

Nevertheless, no fragment of any text or diagram has survived, or at least been recognised as such, neither has a working record of a calculation using a toleta de marteloio‘A trigonometric reduction table to aid navigation by dead reckoning’, used to calculate the actual course sailed when tacking into the wind. Proposed theoretically by Gregory McIntosh (at the 2016 Lisbon workshop) this would have been “a piece of parchment for drawing the sides of triangles for recovering the course” when tacking.

Expressing a strictly artisanal view in a recent article, Joaquim Alves Gaspar and Henrique Leitão observe:

Pre-Mercator nautical charts are complex objects whose inner geometrical properties are only now starting to be understood. Rather than attempts at a faithful geographical depiction of the world, they were tools aimed to accomplish a specific purpose – to support marine navigation – a fact that is often mentioned in contemporary sources. Thus, they carry inside their internal geometry the imprint of the activities of pilots on board, that is, a ‘signature’ of their artisanal origin and of the techniques used to navigate ... nautical charts were deeply influenced by the practices of the artisans who used them, but, simultaneously, such influence was almost invisible to contemporary scholars and present-day historians … first, that historically, nautical charts can only be understood in the context of the specific navigational methods they were intended to support; and second, that a nautical chart should not be considered as a true geographical map but as an instrument for navigation. 315 

Support for the notion that the missing link might have been a diagram rather than a marine chart, can be found in the Liber’s puzzling descriptions of the Tuscan island of Pianosa as quadrangular and Cyprus as a double quadrangle; those terms are more suggestive of classical textual sources. Similar instances are the triangular Sicily and square Cyprus found in some mappaemundi ’World maps’ in Latin (singular, mappamundi). Used to distinguish medieval maps of the world from those of Ptolemy and the portolan charts. 316  Those would not have been helpful characterisations for a sailor. 317  But descriptions of that kind would make more sense if somebody was looking at a simple pelagic diagram emphasising the capes that defined an island’s overall shape, but before any attempt had been made to delineate the coastlines.


Table of Contents


For brief summaries see the Conclusions


 

I.4.   WAYS IN WHICH THE MENTAL MAP MIGHT HAVE BEEN ‘DOWNLOADED’

I.4a. What medium might have been used?

Even if the hypothesis that navigators had been able to build up a comprehensive mental map could be proved, that would, on its own, have little relevance for the origin question. Not until the information had been ‘downloaded’ into graphic form could it have served its conjectured purpose as the foundation for a simple cartographic diagram that could develop into a marine chart.

We might conjure up the germ of the portolan chart in a fanciful exchange between an enquiring passenger (perhaps a pilgrim) and an experienced navigator, in an incident akin (though reversed) to that of an explorer asking an indigenous guide to sketch out a map on the ground. In this instance the questioner might have asked: “Please tell me how far we have come, what places we will be going to, and how long you think it will take?” Drawing out the course, assuming the necessary materials were available, would have surely been the easiest way to answer those questions. As a possibly comparable example, the 10th-century member of the Balkhi School, al-Muqaddasī described how an Arab merchant in Aden, when he was asked for information on the Indian Ocean, “rubbed the sand with his palm and drew the sea on it”. Although the image was ephemeral, it did demonstrate the process of downloading a mental chart. 318 

If such a pelagic diagram existed it would have been logical for it to have been sketched over a circular wind network, where each of the eight or sixteen wind directions ran through the centre of the circle. If so, that would prefigure the network which underlies all surviving portolan charts. 319  It would also mean that the same directional pattern that sailors would later use to lay off their course had previously helped to create those charts in the first place.

How such a diagram might have been drawn is a matter of pure speculation. Vellum was an expensive material (hence its routine reuse as a palimpsest) and it is unlikely that a prepared skin would have been employed for a preparatory pelagic diagram. Nor would paper have been readily available to European sailors around 1200. 320  al-Muqaddasī again provides an interesting 10th-century parallel, when he reported seeing two maps of the Indian Ocean, drawn respectively on paper and cloth. 321 

A more plausible material on which to lay down a geometric diagram of the Mediterranean might have been some kind of textile although the coarseness of sailcloth could mean we have to look elsewhere for the most likely medium, perhaps discarded clothing. On the basis that the diagram would have been constructed from plotted-out courses drawn or described by mariners, it could have been created just as well at sea as in a port. Sailors, whether literate or not, are unlikely to have had access to a quill pen and ink but among the crew there might well have been clerks or others who could have provided those. 322 

I.4b. The downloading process

The main, and most challenging question has always been to provide an even semi-plausible explanation as to how the components for a complete and reliable chart managed to be thought out and laid down cartographically. As a partial recapitulation of what has already been said above, the process of transferring information held in memory into some kind of graphic form, and then elaborating on that, is likely to have had a number of distinct stages, each representing a significant conceptual leap:

  1. It might have started with a single long-distance course, though that could have taken one of two forms: either a simple straight line (perhaps conveyed orally), or a more elaborate record of the stages of an actual journey.
  2. That would need to have been followed by the addition of further courses sharing the same pelagic terminus, which would have allowed the possibility, in time, for the design to grow, incrementally, into an extended network. At that point those involved would have presumably noticed that some repeated termini had been located in slightly different positions. This would have alerted them for the first time to the existence of those errors, thus allowing them to be corrected, whether by moving the terminus along the coast or by adjusting the pelagic distance. It is open to speculation as to how much of that hypothetical network of pelagic courses could have been constructed mentally and how much would have become apparent only once it was in graphic form.
  3. At that stage there might have been the crucial insight that, by setting down those details on a flat surface, the overall pattern would become clear (along with the lacunae) and new routes could be extrapolated from the existing data. Thus a diagram created from memorised pelagic courses could later be used to plot future ones.
  4. Presumably that would have triggered the realisation that coastal outlines could now be sketched in between the already-placed headlands.
  5. That, in turn, would have allowed the addition of the sequence of place-names, a large proportion of which would presumably have formed part of the sailors’ mental store anyway. The imprecise positioning of the toponyms on a portolan chart might endorse the contention here that the names had merely been memorised in the form of a sequential list rather than, as in a portolano (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open- sea (pelagic) routes, being placed in relation to the size of the intervening distances between them.
  6. To be fully functional, the chart also needed to be furnished with a range of conventions, most of which were then apparently unknown to cartography. Among the most obvious of these are an underlying network of 32 wind or compass directions; an indicated map scale; the absence of colouring for the seas; toponyms consistently placed at right-angles to the coast (the more prominent of those written in red), giving the chart a flexible orientation that matched the way it would be turned during use at sea; and the beginnings of a coded symbology for navigational dangers. 323 
  7. In addition to the post-Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) adjustment of the Adriatic, and refinement to the hazard symbols, the other feature which still required development was the handling of the spandrels on the twin-circle networks (the area above and below the point of tangency). This was left un-provided with compass lines on the earliest charts. The Carte Pisane and Avignon chartA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html chart filled in that space awkwardly with supplementary grids, while the Cortona chart’sBased on its archaic appearance, this is considered to be the second oldest surviving portolan chart after the Carte Pisane, dating from the beginning of the 14th century or even earlier. It was first described in 1957 (Biblioteca dell'Accademia Etrusca di Cortona, Port. 105) network ignored the Adriatic entirely. Later charts experimented with a variety of ingenious geometric arrangements for the junction of the twin circles, demonstrating both the still relatively undeveloped nature of the Carte Pisane and the continuing creativity of those unknown early practitioners.
  8. Finally it must have been appreciated that an animal skin, largely untrimmed, might be used to carry a reproducible map of the Mediterranean. [Is there any evidence that entire, unevenly-edged skins had been used by scribes before?] The holes in the neck of the Carte Pisane may indicate a further reason for not trimming the skin down to a neat rectangle. Once it was rolled up, it could then be secured with a strip of leather anchored in that hole.

When the chart first came to be drawn out it is likely that east or south would have been prioritised in its orientation, since dawn and the midday position-sighting are likely to have been the main daytime events for the navigator. However, the shape of the Mediterranean invites a ‘landscape’ presentation (coincidentally matching the animal skin on which the completed charts would later be drawn). 324  There are some indications that, when choosing whether to put north or south at the top, the early charts favoured a southward orientation.

Following on from the above we can speculate that the collaborative input on which this thesis is based could have resulted in further significant advantages in the period during which the portolan chart was being devised and then improved:

This transition from a privately-stored mental network of pelagic courses to a drawn-out diagram is crucial to the thesis of portolan-chart origin set out in these pages. “Like any technical object”, Patrick Gautier Dalché observed, “the marine chart represents an object de pensée (a materialized thought-object)”. 325  As we are contending, it would not logically have been possible for the portolan chart to have developed from any other source than the memorised knowledge of pilots – at least before, say, the 16th century, when adequate navigational instruments had become available. 326  Such a metamorphosis from mental construct to graphic reality can also best explain the “sudden emergence of nautical cartography”, remarked upon by Ramon Pujades. 327 

Until the portolan chart (or its antecedents) emerged, maritime lore must have been broadly static, equally likely to deteriorate as to improve, with the hard-won spatial knowledge of an individual mariner disappearing at his death. Instead, with a graphic alternative, a shared knowledge could be enriched by subsequent generations, in a way similar to that experienced in a literate environment. The change from virtual to tangible allowed information to be first shared, then refined, and subsequently augmented. In that way, the medieval pilots were able to break free from the need for the constant re-invention of the mental map. Once provided with a portolan chart, a ship’s boy might have started with considerably more information about the hydrography of the Mediterranean than a 50-year-old mariner would previously have had locked in his head.

I.4c. The rectification procedure

A single remembered course could never have been more than approximate but, once combined with others originating or concluding at the same points, errors could have been steadily cancelled out. Lo compasso’s’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) pelagic statements include a number of multiple instances of such duplication. About twenty instances, for example, start or end at Malta [or Gozo] 328 as can be seen graphically in Roel Nicolai’s diagram. 329  When faced with conflicting placements of the pelagic termini involved in multiple incoming and outgoing transits, a graphical optimization process could have averaged them out. 329a  Subsequently, the common position could have been tested on later voyages and, where necessary, rectified further. Hence the reliability of the proposed pelagic diagram would not have depended entirely on the ability of medieval mariners to measure distance precisely.

This hypothetical process of positional refinement, although not yet generally accepted, has been stated before, in this case by Ramon Pujades: “It would have been necessary to compile the information culled from a substantial number of crossings, because perfection in terms of representation could increase only as the number of points grew that could be located in respect to each other with relative precision”. 330  Since each pelagic course is in fact two (outward and inward), this would have doubled the possibilities for comparison with an earlier estimate, and as a result lead to possible rectification – part of the necessary process of collective endorsement.

Some of those revisions could have already taken place mentally, although there must have been limits to the complexity of what pilots would have been able to retain in that form. Most would probably have been subsequent additions and refinements, which could have been made only once there was an initial graphic diagram on which to record them. Writing in 1279, near the time that the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) was probably drawn, Egidio Colonna commended the realistic geometry of the portolan chart, writing that sailors “draw a map of the sea on which sea ports, hazards and other such things are described in proportion”. 331 

Because of the lack of intervisibility it would have been natural for there to have been separate mental maps for the different Mediterranean basins: in other words those that were discrete entities in terms of sailing. 332  There would no doubt have been gaps and many inconsistencies – but that could actually have provided part of the impetus for a shared effort to record the network, complete it, and then iron out the mismatched positions. 333 

While the Nicolai thesis (logically if not explicitly) denies the possibility that the medieval mariner could have improved what he was unable to create, we can actually see that process of rectification taking place on the charts that followed the Carte Pisane – most notably in the width of Italy and the Adriatic. 334  Although the broadened shape of Italy is what catches the eye, the error actually concerned the relative position of the unconnected coastlines that frame it. In other words, it was not the result of faulty observation from the seas either side of Italy, nor could the error have been readily appreciated or amended by navigators.

Long after the development stage, in 1403, Francesco BeccariFrancesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library) was to explain that he had been informed about the incorrect positioning of Sardinia. 335  The way in which that error (if it was indeed one) was identified by informants is likely to have mirrored the earlier rectification process when mariners’ experience must have challenged the positions of pelagic termini on the emerging chart.

I.4d. The role of the scribe

Moving on to the replication stage, we might assume that the charts would initially have been copied by the same individuals who were involved in developing them. As the demand grew, a stage must have been reached when the nascent charts were considered sufficiently accurate and complete to be worth wider circulation. The fine and varied detail required by the charts called on special drafting and scribal skills for what was essentially several different documents in one: an underlying mathematical structure formed of compass lines; coastal outlines; navigation danger markings and written toponymy, requiring experience at using inks of different colours; and, as time went on, colour washes. 335a  To preserve the charts’ main purpose, namely its geometric accuracy, only strict workshop discipline could have avoided progressive distortion. This was the main key to the charts’ longevity.

Among the charts produced in 15th-century Venice were some whose creators were also sailors, but it is unlikely that a mariner from two centuries earlier would have possessed the required scribal skills. Pietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated displays a neat and very confident hand, 336 and he had clearly been trained as a scribe. However, there is no indication that he had served at sea; indeed, that seems improbable.

Creativity and imitation need always to be distinguished when dealing with the portolan charts. True ‘chartmakers’ were in a small minority among the generality of artisan ‘chartcopyists’. It is also important to appreciate the contributions that must have been made, at different times, by various classes of individuals to the creation and then replication of the charts. A suggested list might look like this:


Table of Contents


For brief summaries see the Conclusions


 

J. COMPLETING THE PORTOLAN CHART COVERAGE

 


 

J.1.  THE CHARTING OF THE BLACK SEA

It is highly unlikely that anyone would have taken the trouble to describe, let alone chart, an inaccessible sea, hence it was only with the 1204 renewal of access via the Bosphorus that the Black Sea became relevant once more to most Mediterranean mariners. A previous section 338 analysed the description given in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v), and concluded that its author was not taking his information from a marine chart, in the way he had apparently done for the Mediterranean. In other words, the chart that was available to him in 1204 would have terminated at Constantinople. That meant that extending those earlier outlines to include the Black Sea was an entirely new development, evidently starting at some point after 1204. On that interpretation, the Fourth Crusade could have opened up – initially to the Venetians, then later to others – a sea whose hydrography was largely unknown to Mediterranean mariners. This is comparable to the way that the Atlantic coasts would start to emerge on the charts at the beginning of the 14th century.

The sparse details relayed by the Liber referred to small groups of neighbouring places coupled with the intervening distances (albeit mostly lacking the mileage figures) as well as one or two open-sea tracks. That dispersed information might indeed point to the tentative start of the marine survey of the Black Sea. Because there is nothing in that section of the Liber’s text that has been recognised as indicating events later than 1206 – and taking account of the rush that there must surely have been of Venetian merchants taking advantage of long-denied access to eastern goods – the Liber’s text has therefore been given an approximate date here of no later than 1210.

It is surprising that there seems to be no evidence documenting the cartographic development of the Black Sea between the time of the Liber and the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . One point is clear, however, namely the enlarged scale at which the Black Sea was drawn, namely about 3% compared to the Mediterranean. 339  Likewise, the scale later used for the Atlantic coasts was smaller than that for the Mediterranean. Those two deviations from the central norm, possibly occurring at either end of the 13th century, point to the work of successors to the original progenitors of the portolan charts, who were starting from different premises. Although the Atlantic scale would be corrected by Francesco BeccariFrancesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library) in 1403, the overstated size of the Black Sea continued for centuries, perhaps a reflection of contrasting priorities or because the navigating conditions there were different from those elsewhere.

Given this evidential silence, there is no means of testing the hypothesis that the Black Sea’s outlines could have been formed by joining up coastal sections. Those might have focused on, and worked out from, the major trading ports, as scan be seen in the placement of the scattered toponyms reported in the Liber. 340 

To assess the sophistication of the coastal outlines and the density of the toponymy, it is therefore necessary to turn to other sources from that general period. It has also to be pointed out that none of the documents involved can be dated with any confidence. Nevertheless, the limited details that can be retrieved from the Carte Pisane in its present state seems to indicate similarity with the coeval sources, to be discussed shortly.

After a brief look at how the Black Sea differed in fundamental ways from the areas covered by that earlier (Mediterranean-only) chart, a conjectural attempt will be made to reconstruct the likely processes involved in defining the Black Sea’s outlines. If such an exercise has already been carried out, I have missed it.

J.1a. The peculiarities of the Black Sea

As argued throughout this ‘Origins’ essay, the Mediterranean heart of the portolan chart was not built up piecemeal but should instead be seen as a visible manifestation of a mental chart formed out of a geometric grid of numerous remembered open-sea courses across that sea. It is assumed to have appeared, almost fully formed, and needing only a period of rectification to turn it into a reliable navigation aid. What had assisted that process – perhaps even prompted it – was the presence of a range of islands, large or small, which could supply innumerable bearings, for use in a process here dubbed ’inadvertent triangulation’An invented term for the hypothetical process by which pilots, before there was a marine chart, could have built up a mental network of the interrelationships between Mediterranean headlands, by means of observed directions and estimated distances. No mathematical calculations would have been involved. It was that which would have provided a reliable framework for a marine chart.

In contrast to the enclosed Mediterranean, those attempting to chart the North Sea Atlantic coasts – at around the time that the Black Sea exercise was being completed, perhaps a little after 1300 – were faced with a lack of corroborative bearings from convenient islands, which helps explain the hydrographic problems they encountered and the lasting deficiencies in the coastal outlines that resulted.

In other words, mapping the Black Sea presented difficulties and opportunities not experienced in either the Mediterranean or Atlantic instances. At 1,175 km in width, the Black Sea was far smaller than the Mediterranean and, in contrast to the complexities in the northern half of that sea, offered a broadly uncomplicated coastline. Unlike the Mediterranean, all ships had to enter the sea at a single point, the narrow Bosphorus strait, and then head off to their destination – directly, if in a galley. Based on that, it might have been expected that the initial charting would have created a network of pelagic courses spanning out from that single entry point, in contrast to the Mediterranean’s large choice of pelagic termini. For the Black Sea, unhindered by islands, bearings could have been readily memorised and used to create a reliable geometric framework that would define the sea’s perimeter. The few pelagic courses reported in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v), some from ostano at the mouth of the Bosphorus and others with a focus on the Kerch Strait that leads into the Sea of Azov, might be the start of that process. But, if so, it could never have been completed, as demonstrated by the continued geometric distortion to the south-eastern coastline.

When considering any sources for the Black Sea’s outlines and toponymy which might have provided building blocks for those who were working to extend the portolan chart to the east, the obvious candidates would be the second century CE, Alexandrian geographer, Ptolemy, and al-Idrīsī, the creator of a vast world map in 1154, the Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text.

Coverage of the Black Sea in Ptolemy’s Geographia is split between several sheets: Prima Asiae (southern coast), Prima & Tertia Asiae (east coast), Secunda Asiae & Octava Europe (Crimea and the north coast), and Nona Europe (west coast). 341  Unless the sections are joined up, this means that only the world map provides the whole sea in a single view, necessarily at a small scale. Overall, Ptolemy’s version is surprisingly plausible, and certainly superior to the earliest attempts by the portolan-chartmakers, avoiding the distorted shape of the south-east section, as described below. This supplies evidence that even if Ptolemy’s work was being used it was not yet being imitated. 342 

Like some other Islamic geographers, al-Idrīsī is thought to have made use of the Ptolemaic outlines, but that could not have applied to the Black Sea. The unrecognisable shape he gives to that sea, with its imaginary islands, some treated as equivalent in size to Corsica, could not have borrowed anything from Ptolemy.

J.1b. 13th-century developments

It might have been hoped that 13th-century records would have helped to reveal how the Black Sea’s outlines were captured. Unfortunately, the available sources fall between the slender and the non-existent, and what there is comes without secure dating. There is nothing between the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) , with its meagre 13 toponyms, and a more detailed pilot guide, Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) with 104. Besides those two witnesses are a small group of early, unsigned and undated, charts which might date to the period between the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) and the first dated chart, Pietro Vesconte’sPietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated of 1311. 342a  Whereas the process of defining the Atlantic coasts of the North Sea can be progressively documented in charts that followed the Carte Pisane, in the Black Sea instance. because of a lack of written evidence, we have no witnesses to the early years of its surveying history.

Lo compasso, whose text (incorporating amendments) is thought to date within the period 1260-1296, includes a section on the Black Sea. 343  However, that comes at the end of the volume and in Alessandra Debanne’s opinion was ‘probably’ missing from the original form of that work, only being added for the surviving example. 344  Since the volume bears the date 1296, it is hard to argue that the Black Sea section is any earlier than that, thus placing it, in this context, later than the Carte Pisane. On that basis, this leaves the period 1210-70 without visual or textual evidence about the cartography of the Black Sea. 345  Investigation is further hampered by the Carte Pisane’s twin limitations: that its eastern third was (intentionally) omitted, and that serious damage to the vellum in the Black Sea area means that some outlines and a number of place-names have been lost.

J.1c. Toponymy

The resulting omission from the Carte Pisane of Tana, Savastopoli, Trapesonda, etc., might seem to imply a lack of awareness of their significance. However it is more likely that the author, with restricted space available, kept to the dimensions of earlier charts, whose eastern edge followed the longitude of the Levant coastline, while making sure, at the western end, to include all of the Iberian Peninsula. 346  As a result, it is no longer possible to get a sense of the sea’s overall shape on the Carte Pisane, and much of our knowledge of its toponymy derives from tentative readings on a facsimile made in 1852, before some of the damage had occurred. 347 

Toponyms are easier to compare than coastal outlines but in this case they are an imprecise guide to the cartographic development of the Black Sea. No more than 25 Black Sea names can now be retrieved from the Carte Pisane. Yet, of that small number, ten do not appear on Lo compasso and eight are absent from the (supposedly) second oldest survivor, the Cortona chart,Based on its archaic appearance, this is considered to be the second oldest surviving portolan chart after the Carte Pisane, dating from the beginning of the 14th century or even earlier. It was first described in 1957 (Biblioteca dell'Accademia Etrusca di Cortona, Port. 105) while seven are not repeated on either. Lo compasso and the Cortona chart have an identical number of Black Sea toponyms (104), which might point to conformity. However, in each case half of their total is not found on the other. In other words, there was a marked lack of uniformity in the second half of the 13th century about the selection of names around the perimeter of the Black Sea. As happened elsewhere, the Vesconte chart of 1311 and his atlas of 1313 mark the beginning of what would become a stable toponymic sequence, increasing steadily afterwards. 348 

J. 1d. The shape of the Black Sea

The predictable way to have surveyed the Black Sea would have been as a two-pronged effort, by documenting the coastal locations and their intervening distances, on the one hand, and building up a geometric network of pelagic courses so as to fix the sea’s perimeter, on the other. Lo compasso ’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) , which includes over 1,200 open-sea pelagic courses (Peleio) for the Mediterranean, omits those entirely for the Black Sea. As, indeed, do later portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes, which further argues against there having been any systematic documentation of pelagic tracks in that sea. Since the coastal outlines on the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) are now largely illegible, this means that the first available marine chart of the Black Sea is represented by the Cortona chartBased on its archaic appearance, this is considered to be the second oldest surviving portolan chart after the Carte Pisane, dating from the beginning of the 14th century or even earlier. It was first described in 1957 (Biblioteca dell'Accademia Etrusca di Cortona, Port. 105).

The lack of geometric underpinning is confirmed by distortions to the overall shape on the Cortona chart, particularly in the eastern half, which is noticeably misaligned. The other undated charts that followed the Carte Pisane are not relevant: the Avignon chartA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html fragment does not extend east beyond Italy, and the Lucca chartDiscovered in 2000 in the city archives, this is visually very different from other charts from the 1st quarter of the 14th century (Archivio di Stato, Lucca, Fragmenta Codicum, Sala 40, Cornice 194/1) includes only the south-west portion of the Black Sea.

Hence the focus must turn to the 1311 Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated chart and that in the Riccardiana LibraryThe oldest Genoese chart, probably dating from the second decade of the 14th century (Biblioteca Riccardiana, Florence, 3827), perhaps of roughly the same date. Those show similar improvements to the shapes of Crimea, the Sea of Azov and the south-east, but there is still no appreciation that the lowest points along the south coast (near to either end) are on the same latitude, or that the moving up of that coastline has caused the east coast to be compressed. Nevertheless, that imperfect outline must have been thought acceptable, since it was left uncorrected and can still be seen in the work of Grazioso Benincasa An ex-ship captain, he left us a range of clearly-drawn charts and atlases (1461-82) and a written portolano (1435-45) in the 1460s, and on subsequent charts. As a result, after being worked on for up to a century – with a magnetic compass certainly available for much of that time and a relatively uncomplicated coastline – the outline of the Black Sea ended up as less realistic than those that had been achieved across the entire Mediterranean (and particularly the Adriatic and Aegean seas) prior to 1204.

The likely explanation for what might not perhaps have been considered as a shortcoming by the charts’ users, focuses on the nature of that sea and the navigational procedures within it. Islands dominate the Mediterranean, and hence the sailing practices in its waters, but the Black Sea has none of any significance. So without islands that needed to be skirted round or that could serve as waypoints, Black Sea navigation is likely to have involved, for the most part, a voyage, starting at the sole entrance point, the Bosphorus, and heading more or less directly to the destination. Most of the termini would have been in the north, along the Crimean coastline or on to Tana[is] at the head of the Sea of Azov. The dangers facing pilots were also concentrated in the north, in the form of extended shoals, which the portolan charts took good care to illustrate. Nevertheless, for those heading east, say to savastopoli (Sukhumi) or trebisond (Trabzon), a dog-leg would be involved. Whether they stuck to the coast or set out to sea and changed direction at a certain point, they could not have followed a single bearing into that large, misplaced south-eastern bay. Instead, they would presumably have memorised the successive bearings involved.

Given that the reason for Mediterranean sailors venturing into the Black Sea was primarily, if not entirely, related to the various colonies and trading posts, it is likely that a correct sequence of coastal toponyms would have had more significance for the portolan-chart users than distortions in the placement of the coastlines in the south-east. That interpretation would fit in with the wider assertion that the portolan charts were strictly pragmatic navigational tools, adaptable to changing purposes and supplying precision only where it was needed.


Table of Contents


For brief summaries see the Conclusions


 

J.2.   CHARTING THE ATLANTIC COASTS AND THE FINAL MEDITERRANEAN IMPROVEMENTS

The last major development concerned the Atlantic coasts. Seen schematically on the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) in a pre-cartographic form that must have been based merely on hearsay, Europe’s Atlantic shores would gradually take shape thereafter. The steadily growing appreciation of the coastal outlines, particularly for the British Isles, along with the region’s littoral toponymy, can conveniently be observed in the twenty years of productions from the atelier of Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated . There would be little amendment thereafter. That is the earliest occasion – followed by the addition of the Canary Islands in the 14th century and the Portuguese charting of Africa’s west coast in the 15th century – where we are able to observe significant chart improvements.

To avoid repetition, the reader is referred for the details about the Atlantic coasts to the relevant section of the 2015 essay on the Carte Pisane. As an update to the comments there about the British Isles see Jacques Mille’s interpretation of the coverage of that area on the Avignon chartA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html. Occasional extensions into the Baltic, an area where few Mediterranean vessels ventured, provided more variety in the cartographic coverage than refinement. 349 

As regards the Mediterranean, the broad conclusion would be that few of the outlines seen on the Carte Pisane were corrected until the earliest productions of Pietro Vesconte (1311-13). After some additional improvements by Angelino DulcetiAngelino Dalorto or Dulceti was a Genoese who worked in Palma, Majorca, leaving us dated charts of 1330 and 1339. His were the first to introduce inland and illustrative details in the 1330s, no significant attempts at further refinement have been noted. As a result, the 1330s outline would remain in place for centuries afterwards. Each of the small modifications made to coastal and insular outlines between the Carte Pisane (c.1270) and 1311, and then those observed in the charts of Vesconte and Dulceti, were probably unconnected with one another. This presumably reflects the critical observations made by countless pilots, and the subsequent responsiveness of chartmakers: in other words proof of a collaborative process that had been built into the DNA of the portolan chart from the outset.


Table of Contents


For brief summaries see the Conclusions


 

K. THE CHARTS’ MAIN ELEMENTS

In an attempt to isolate the main elements of the portolan chart, four aspects will be examined in turn: the outlines of the mainland coasts, islands and rivers; the hazards facing shipping; the charts’ toponymy; and their illustrative and textual features.

 


 

K.1.   COASTAL OUTLINES

K.1a. What was the source for the coastal outlines?

The written coastal itineraries have already been discussed. 350  But what of their cartographic treatment; what might have been the source behind the outlines of the mainland and insular coasts?

It can confidently be stated that the littoral toponymic sequence is unconnected to the pelagic courses. They represent different types of information, for different purposes, and almost certainly with a different origin. However, there are competing theories about the place of the coastal outlines in the origins story, and a number of possible explanations for their source:

1. Provided, in sections, from the visual memories of mariners

Roel Nicolai has commented that:

Most scholars who endorse the medieval origin hypothesis assume the geometric basis of the charts to be a geodetic control network, consisting of the azimuths and distances between points along the coast, measured as a ship travelled along the coast (per starea) and supplemented by observations on cross-basin (per peleio) routes. 351 

It is possible that some kind of what could be loosely termed a coastal survey(s) might have taken place prior to the downloading of the pelagic diagram, since partial sequences of names along the coast must always have been known to those engaged in the cabotage trade. Thus adding an attempted graphic accompaniment would have been a logical step. But if that had happened the result is unlikely to have been realistic. 352  We could speculate that it might have had a similar appearance to the Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text, i.e. with large parts unrecognisable. Hence, if the coastal outlines had come first they would have had to be heavily adjusted afterwards so as to fit into the confirmed positions of the pelagic termini.

2. Essentially textual, a ‘dot-to-dot’ exercise

Alternatively, the suggestion that somebody might have taken a ruler to the coastal itinerary of a portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes such as Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396), simply read off the distance and direction from one port to the next, and then sketched in the intervening coastal outline – as per the experiment of Jonathan Lanman in 1987 353 – is no longer considered plausible. 354 

3. Inserted later as infilling to a pelagic diagram

On the basis that the pelagic diagram came first, adding the coasts would have involved little more than filling in the gaps between those positionally-accurate termini. This is the explanation favoured in this essay. According to that contention, the chart’s fully recognisable overall outlines for the Mediterranean would be due to the relative geometric precision of those pelagic termini, and not to the drawing in of the shorelines.

As a partial corrective to that generalisation about the broad-brush approach to the mainland coastlines, Jacques Mille, who has made a close study of the Provençal coastline, found recognisable features in the 1313 atlas by Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated , in particular the treatment of the Giens Peninsula. 355  However, that is relatively close to the west coast of Italy, where the charts evidently emerged, and that area may prove to have been treated with greater care. An overall examination of the coastline treatment would be a useful subject for future research.

In any event, we need to stand back from a 21st-century perspective, with its inbuilt emphasis on accuracy, and attempt to seek an answer from the charts themselves. In particular, the realism reflected in the positional precision of the pelagic termini has to be contrasted with the generally formalised treatment of the coastal configurations between adjacent headlands, which is considered next.

K.1b. How were the coasts demarcated?

On our oldest surviving chart, the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , the general trend of the coasts is respected, with major bays and promontories indicated, and rivers denoted with two short parallel lines. But whatever lay between was already being treated in a loose, generalised way. This left little on which to anchor the position of the ports and rivers, but neither does that seem to have been attempted.

Pietro and Perrino VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated began to draw capes with chisel ends, and with broader versions of that same device for the short sections between rivers. Later, for example in the work of Grazioso Benincasa An ex-ship captain, he left us a range of clearly-drawn charts and atlases (1461-82) and a written portolano (1435-45) in the mid-15th century, between the one-size-fits-all river symbols and the bays as conventional scoops, the over-emphasised headlands are conveyed by means of a variety of artificial shapes. Those are reminiscent, to us at least, of everyday objects (even if the similarities are accidental) such as tuning forks, jigsaw puzzle pieces, battlements, etc. All this underlines the greater importance, to the charts’ creators and users alike, of the promontories (which were often pelagic termini as well), when contrasted with the casual treatment accorded to the coastal configurations between them.

I was only recently made aware, by Zoltán Biedermann, that some stretches of the coast were traditionally represented in different, specific ways. 356  These alternatives are already apparent in the early 14th-century atlases of Pietro Vesconte. Contrast, for example, the treatment of the uncharted north coast of Scotland, which is rendered by means of little more than a single wavy line, when compared to the intricacies of the Istrian peninsula in the north Adriatic. Other stretches fall between those two extremes. It seems likely that these distinctions had a purpose, which was probably descriptive of the differences, first, between the known and unknown, and, second, between stretches with few distinguishing features and those where rocky shorelines were present, characterised by cliffs, small inlets, reefs, and so on. 357 

This aspect deserves future study to see if these distinct types of coastline representation can be classified into a typology, and, if so, how realistically that matched with reality. The value for mariners of a visual guide to the shore’s appearance when approaching an unknown coast would be obvious. It is strange that so important a feature seems to have been overlooked by all of us, past and present. However, assuming that the Carte Pisane reflects the style of its immediate antecedents, this possible further innovation must be credited to one of the chartmakers that followed later, perhaps Vesconte, and hence it has no direct bearing on the origin question itself. 358 

K.1c. Rivers

In general, portolan charts conveyed little about a river’s size, course or source, concentrating instead on the estuaries. However, exceptions were made for the major deltas, as well as a handful of the more significant rivers, such as the Thames, Guadalquivir, Rhône, Arno, Tiber and Nile, which are slightly enlarged and extended inland. That refinement seems likely to have been designed to indicate that those rivers were navigable by seagoing vessels at least up as far as their major inland port. That, combined with the fact that few of the rivers were named on the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , might seem to indicate that the portolan charts’ initial focus was on seaborne rather than riverine trade, often naming the ports at their entrance rather than the river itself.

Dating probably from a little after the Carte Pisane, the Cortona chartBased on its archaic appearance, this is considered to be the second oldest surviving portolan chart after the Carte Pisane, dating from the beginning of the 14th century or even earlier. It was first described in 1957 (Biblioteca dell'Accademia Etrusca di Cortona, Port. 105) introduces inland detail for the Danube and Nile, as well as a river at Latakia (liche), Syria. 358a  By 1313, Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated was using island-like segments, in different colours, to symbolise the complexity of such major deltas as the Danube, Dnieper [Dnipro] and Nile. The Danube is the second largest delta in Europe but is indicated on the charts by no more than the two main outlets into the Black Sea at that time, the Sulina and Stantul Gheorghe. This reticence was presumably a response to the shifting channels and large areas of marshland involved. As with other symbols, their meaning must have been left to oral explanation.

However, many rivers were navigable, if only via transhipment into smaller vessels. In those cases the inland ports might be named even if some, for example Cologne, Paris or Seville, were a long way upriver. That information would clearly have been important for merchants but it was only the Catalan-style charts from 1330 onwards that introduced generalised courses for the major rivers, as well as the cities along them, thus indirectly offering information about upstream navigation. 359 

Perhaps coincidentally, because both the river itself and the town at its mouth had navigational significance, the symbol for the river's mouth (formed of short parallel lines) provided a neat prompt at the scribal stage, showing where the toponyms should indeed be precisely positioned. A good example of this is along Italy’s Adriatic coast, where each name is stationed alongside the matching river symbol.

As always when dealing with portolan charts, close study is rewarding. Because it is natural to focus attention on the more visual or significant features, minor details that can give insights to a cartographic historian can easily be overlooked. The previous section on coastlines offered a good example of what is almost certainly another feature unique to the portolan chart, namely alternative representations of the shoreline. The cartographic language used to denote smaller rivers may well be another.

It might have been expected that the quick and easy method of drawing the coast as a single continuous line would have been adopted. Instead, as can already be seen on the Carte Pisane, pairs of short parallel lines were used to denote river estuaries. This was a formalised symbol that took no note of the difference in size between the medium and small rivers. That ingenious, minimalist device has not apparently been noted in earlier cartography. Because the ink line turns briefly inland and then stops abruptly, to be taken up again for the start of the next stretch, the draftsman had to raise his pen and then replace it, so as to indicate the river’s other shore, before continuing along the coast. Like the intricate symbols for offshore dangers 360 no effort seems to have been made to find drafting shortcuts. 361  However, there might be one exception, although this point was not thoroughly checked, because some of what would become river mouths on the Vesconte charts had previously appeared as small inlets on the Carte Pisane and Cortona chart (i.e. they had initially been drawn as part of the continuous coastal outline).

K.1d. Islands

For anyone navigating the northern half of the Mediterranean, islands played an important role, since they provided copious reference points to help fix a ship’s position. 362  The way that the charts handled the islands of different sizes gives us clues as to how that information might have been used by mariners and, at the same time, how it was dealt with by the chartmakers.

The portolan charts’ treatment of the Mediterranean islands was imaginative and, in some respects, unique. It was also, at first glance, erratic. Why was there this marked difference between the portrayal of the large and the smaller Aegean islands? Start, for example, with the handling of the seven largest islands: Majorca, Corsica, Sardinia, Sicily, Euboea, Crete and Cyprus. Their realistic and consistent shapes point to the likelihood that they were part of the direct image-transfer process involving the mainland coastlines. That would have been logical, because coasting along a large island is effectively the same for a pilot as travelling along the mainland, and the island headlands, which were required for navigation purposes, would have needed to be precisely located there as well. However, neither that proposition, nor the question as to how those larger islands were placed in relation to the adjacent coastline, seem to have been tested cartometrically, and there sometimes appear to be minor variations in an island’s overall position in the sea.

As to their outlines, five of those larger islands had already reached what was effectively their final forms on the early work of Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated (1311-13). Only Majorca and Crete had to wait until the 1330s for the improvements seen on the charts of Angelino DulcetiAngelino Dalorto or Dulceti was a Genoese who worked in Palma, Majorca, leaving us dated charts of 1330 and 1339. His were the first to introduce inland and illustrative details. Those outlines are always recognisable and, in the case of Sardinia, Sicily and Crete, notably realistic, so much so that there would only be modest improvements later. 363 

By contrast, the smaller islands were apparently copied freehand. It must have been realised during the charts’ formative period in the early 14th century that it was not necessary to devote time trying to record and reproduce the precise shapes of the lesser islands. There is an obvious logic behind this. The information a mariner required about a small island could be reduced to no more than three parameters: its location, approximate size and name. Since the helmsman would be passing between two islands, rather than along an extended coastline, that was all he wanted to know from his chart. However, he would have needed to call on another type of information for determining his position – the memorised appearance of the respective coastal profiles – something that the chart could not supply.

The first hints of what would prove to be an unusual refinement in the portrayal of the smaller islands can be seen already in the Carte Pisane’sAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) treatment of one or two of the Aegean islands, for instance, Skyros (squur?) and Amorgos (mergo), which is shown as a castellated wall. These are a foretaste of the distinctive, and wholly imaginary, outlines, which would, in the work of Vesconte and Angelino Dulceti be developed into fully-fledged ‘signature’ shapes [Powerpoint, Slides 18 & 19]. Those were not facsimiles of reality but rather specific, easily memorised logos, which were found to be useful enough to be generally adopted and then repeated for centuries. Some island groups elsewhere were treated similarly, particularly those along the eastern Adriatic. This conceptual leap, which would be fully developed as a mnemonic device only some decades after the Carte Pisane, is otherwise unknown in the history of cartography. 364  It is unlikely that the architects of the Dubai ‘Universe’ were aware that they were not the first to invent island shapes [Powerpoint, Slide 20].

From the outset, the portolan chartmakers took great care to label each island with its toponym. Sometimes, because the coastlines needed to be left free for the depiction of marine hazards, the toponym of a nearby island or offshore danger might be inserted into the sequence of coastal names. Sailors would have had to learn to identify which offshore feature was being referred to in each case. 365  This is a further indication of the importance seamen assigned to islands and, likewise, to marine hazards.

K.1e. Charting the Aegean archipelago

Pelagic courses in the Aegean – for example those described in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) and depicted in the diagram at the end of Patrick Gautier Dalché’s edition (1995) [Powerpoint, Slide 11] as well as Joaquim Alves Gaspar’s 2019 article 366 – were, of necessity, relatively short and usually broken into sections. Those would not have provided a reliable underpinning for a chart of the Aegean in the way this essay is claiming that they did for the Mediterranean.

So how would medieval sailors have managed to create and memorise a geometric network that would bind the Aegean archipelago into a single cartographic whole? It seems that they would have needed to construct the mental map of the sea piecemeal, a process made more difficult by the unusually complicated coastline that encircles it on three sides. Of course, if all that mattered was the route through to the Black Sea then it could have been reduced to one or two mental itineraries. But that would not have contributed much to the overall picture of the archipelago.

Since the Aegean could not have been visualised as a whole, it seems inescapable, in this case at least, that something akin to an actual survey must have been carried out. To have plotted the entire network, as seen on the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , it would have been necessary to locate the position of every island relative to the others (even if only approximately) and, where relevant, to the mainland coastline as well. Whereas the mental-map origin theory proposes that the Mediterranean coastlines and toponymy were later infillings to the web of pelagic courses on the true (lost) urdocument, 367 in the case of the Aegean that proceeding must have been reversed. The detailed data would need to have been collected first, at the level of small groups of islands which could then be joined up.

It is not suggested that anybody would have systematically set out to capture the intricate patterns formed by the overall archipelago, and they would certainly not have been motivated by anything approaching a modern concern for accuracy and completeness. Nor is it likely that a single individual would have visited all the islands; any more than the author of the earliest isolario, Cristoforo Buondelmonti, was engaged in a primarily geographic survey when he gathered material for his Liber insularum arcipelagi around 1420. 368  The more likely scenario would have involved the collaborative sharing and combining of overlapping personal experiences, as well as the adjustment stage that must have been necessary to reconcile contradictions and correct errors (though not all of them).

The distortions in the overall shape of the Aegean’s coastline, and some imprecision in the placement of the individual islands that can be seen on the Carte Pisane, are the inevitable result of the inherent difficulties, as well as the limited means at a medieval pilot’s disposal. Despite those restraints, the importance of the Aegean was such that some portolan charts, among them the oldest surviving atlas, Pietro Vesconte’sPietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated of 1313, treated it separately, and at a larger scale than the rest. 369  Overall, the portolan charts’ survey of the Aegean is remarkable, and one that can be contrasted with the Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text, which shows around 30 of the 100 islands and islets (most with their names), but presented with non-specific shapes and with only a minor range in their sizes. 370 

The specific characteristics of the Aegean invite speculation as to how medieval pilots navigated through it. Besides those ships sailing specifically to the numerous (mostly Venetian) colonies, strongholds and trading posts, there was a steady flow of vessels making their way to and from the Black Sea. No doubt some repeated voyages would have followed standard routes, at least when the expected wind was blowing. But how might the details of a preferred, necessarily zigzag, course have been mentally retained by the helmsman? It is fair to assume that he would have stored in his memory pictures of the distinguishing appearance of the flank of each island he would be passing. He would remember each by its name and, from about 1320, by its mnemonic ‘signature’ shape and colour, 371 and recall which had to be left to port and which to starboard, as well as the identity of the ones that loomed up ahead. Because there is no direct route through the archipelago, the frequent changes of direction (recorded in terms of the wind compass) would also have formed part of the navigator’s composite memory and thus helped to confirm the relative positions of those islands.

Despite the contribution of the portolan charts, future mapmakers continued to have difficulty depicting the archipelago, exemplified by the faltering attempt of Edward Wells in 1700, when tutoring the son of the future Queen of England [ Powerpoint, Slide 21].


Table of Contents


For brief summaries see the Conclusions


 

K.2.   NAVIGATIONAL DANGERS

As far as I am aware, one of the four most significant features of the undecorated, functional portolan chart – the others being the relative precision in the placement of the Mediterranean’s headlands, the coastal outlines that link those, and the charts’ toponymy – has never played a part in the discussion about their origins. Indeed this element has received very little attention at all. It is probably no coincidence that one of the few people to look closely into the navigational dangers depicted on the portolan charts should have been the British hydrographic surveyor, Rear Admiral William Henry Smyth in 1854. 372 

The understandable fears of medieval mariners will often have centred on weather or piracy, both of which fall outside the remit of a chart. But foreknowledge of offshore dangers could significantly reduce the risk that they would find themselves in jeopardy, or even be wrecked. In order to warn navigators, therefore, the hazards they faced – more often close to the shore – were indicated on the charts by means of coded symbols. Whereas the threats depicted on the mappaemundi’World maps’ in Latin (singular, mappamundi). Used to distinguish medieval maps of the world from those of Ptolemy and the portolan charts were fictitious and serve as reflections of human imagination and nightmares, the navigational hazards on the portolan charts were all too real.

Throughout 2015, I made a study of those hazards on the portolan charts and the early portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes in the expert company of Captain Michael Barritt, former Hydrographer of the [UK] Navy, now newly published. 373  As a result of our analysis, it is now clear that the perils threatening navigation need to be considered as having, at the very least, comparable importance for the charts’ users as the much-studied coastal outlines, and the toponymy that marched inside them.

Many of the hazards would have been recognised from the earliest times and must surely have formed an important part of a sailor's training, in eras preceding the charts and then continuing into their period of use. It is not surprising therefore that, from the outset, the portolan chartmakers paid close attention to such features. They did so by devising a new visual language, formed of a simple but effective series of symbols involving crosses and dots, in red or black, which enabled the nature, position and extent of each significant hazard to be roughly depicted. Isolated rocks just above or below the water were usually shown with crosses, while shoals and sandbanks were normally marked with dots 374 [Powerpoint, Slides 22 & 23].

Although the portolani, and particularly Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396), might refer to those dangers and even describe their general nature and approximate location, only a graphic document could indicate both aspects with any precision. The Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , along with the unsigned charts that followed it and the earliest productions of the VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated workshop, include the first graphical representations of several of these features. 375  These would be steadily developed during the 14th century, incidentally providing further evidence of the chartmakers’ ingenuity.

The portolan chart provided the only effective means of conveying a category of information that was vital for sailor’s safe-keeping. Translating an oral description of what had been directly experienced into visual form was a far greater challenge for chartmakers than introducing extra place-names. Nevertheless – and this remains to be tested in detail – the steady introduction of new hazards onto the charts seems to have matched the introduction of new toponyms. The portolan charts were never more relevant than when they added details of localised hazards, allowing those to be widely shared.

K.2a. Earliest mentions

In the context of the charts’ origin it can be noted that the Skerki Bank, to the south-west of Sicily and probably the single most treacherous feature in the Mediterranean, is named and depicted on the Carte Pisane, as well as being referred to in both the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) and Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) [Powerpoint, Slide 24]. The Carte PisaneAccepted as the oldest surviving portolan chart, c .1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) also shows, prominently, two offshore features to the south and east of the Skerki Bank: the Bancs de Kerkennah (Tunisia) and the Shoals of Sirte (Libya), the latter much feared by the ancients.

It seems likely that some such warnings to sailors would also have been present, albeit in rudimentary form, on the antecedents of the portolan chart, since they would have been preserved in sailors’ memories in the same way as the pelagic courses. The earliest known unambiguous reference to the use of the portolan charts at sea, also emphasises the importance of the warning they carry about marine perils. In Egidio Colonna’s De Regimine Principum (1279), he explained that sailors:

seeing the dangers of the sea and wanting to avoid wrecking their own ships, draw a map of the sea on which sea ports, hazards and other such things are described in proportion, from which sailors, looking at them attentively, immediately perceive where they should go and where they are and in which places they should be careful. 376 

K.2b. The treatment of dangers in the portolani and chart compared

The incorporation into a pilot guide of references to offshore dangers was already more complicated than the gathering of toponyms, or the simple statements of distance and direction from one cape, harbour or island to another. Whereas the early written guide could tell the sailor roughly how far it was, say, from Tunis to southern Sardinia, and indeed the initial course to steer, it would not help him avoid the wreck-strewn barrier of the Skerki Bank [Powerpoint, Slide 24].

Patrick Gautier Dalché identifies in the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) a reference to that feature, which is there given the early form of its name, chilbi. 377  Though the nature of the danger is left unspecified, it is placed, with reasonable accuracy – in terms of their respective directions and distances in 'miles' [milliara] – in relation to Trapani on Sicily's west coast and Isola Marettimo to the west of that, as well as to Tunisia's Cape Bon and the island of Gimari [Djamour El Kébir] in the Gulf of Tunis. 378  Likewise with Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396), it is theoretically possible to triangulate the various supplied directions between what it terms the quilbo shoal, to ports, headlands and islands in its vicinity. But would anybody have wanted to comb through the ten dispersed references to the Skerki Bank in that un-indexed text to determine those facts? 379 

Indeed, it can plausibly be argued that among the likely reasons for the charts' creation in the first place was the plotting of those navigational dangers, in a way that revealed their location, extent and nature. In the time-and-money equation for a master chartmaker, the sheer number of those warning symbols – perhaps as many as 3,500 ink crosses or separate dots on a single chart or atlas 380 – and the care with which they were precisely replicated over centuries, must have represented a significant outlay, thus underlining the importance accorded to that feature.

Kevin Sheehan, an experienced cartographic draftsman, provides useful information in his 2014 doctoral thesis about the way that the charts were drawn. 381  As a result of his carefully documented copying of three portolan charts, according to what seemed to be the most likely contemporary methods, he was able to estimate that producing an undecorated chart of the full usual extent would have taken around three weeks. 382  Breaking down the separate elements of his chosen model – which excluded the Atlantic, eastern Mediterranean and Black Sea – he found that the rhumbline network took about four hours to copy, the ‘hydrography’ and toponymy about twelve each and the combined scales, colour and ‘other’, 11.5 hours. 383  Unfortunately, it is not possible to extract the danger symbols from those figures because those in black ink were subsumed into the hydrography total and the red dots are included with the red-inked names in the toponymy figure. Nevertheless, it is likely that the time spent on depicting the offshore hazards would have been comparable to that devoted to the outlines and toponymy.

The Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) includes a limited number of those warnings, whereas Lo compasso is liberally provided with them. Several of those referred to on the latter are not seen on charts until considerably later. In a detailed study of France’s south coast on the Avignon chartA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html , Jacques Mille found that some of Lo compasso’s descriptions were as good as their first cartographic depictions on the 15th-century charts of Francesco and Batista Beccari Francesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library). 384  It is not clear though how that portolano’s author was able, in those cases at least, to pre-empt the chartmakers by well over a century. 385 

K.2c. How were the dangers recorded and how did those get onto the charts?

The study carried out by Michael Barritt and myself identified 96 clear threats to navigation (both then and now), almost all of them named. 386  54 of those were noted on the portolan charts. The remainder, instead or as well, can be seen in the 13th-century portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes or their successors. Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) already includes 22 of the 54 hazards found on the charts. Additions to that number were made in the 14th century and a further 20 after 1400. 387  Even though some of the later introductions can be shown to be imaginary, taken together they represent perhaps the most significant updating to the charts, if toponymy is left to one side.

Although those dangers would certainly have had local names bestowed on them, most are depicted anonymously on the charts. In Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) they are usually referred to in generic terms, as scoglie (rocks or reefs) or seche (shoals). 388  This lack of an identifying name may help to explain why these hazards have been little discussed by historians. Yet 43 instances are referred to by name in Lo compasso – as distinct from just thirteen in the earlier LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v), whose clerically-influenced author evidently considered navigational information to be of less interest. 389  Attempting to match those brief textual mentions with what can be recognised on today’s marine charts could be a valuable project for future research.

Confusingly, a number of the dangers that were indeed named on the charts were placed by the draftsmen in the general toponymic sequence, and thus, at first glance, presented as if they were land features. 390  Absence of space in the sea nearby might sometimes have been the reason for that, though not generally. But are those 'inappropriate' names 'interlopers' or do they rather point to the need to see the charts through their users’ eyes and thus upgrade the contemporary importance attached by them to such offshore features, sufficiently well known for their names to have been squeezed into the coastal sequence?

A question that does not seem to have been considered before is how did those patterns of rocks and shoals find their way onto the charts in the first place, in forms that would rapidly become standardised through precise copying? It is easy to imagine place-names being conveyed orally to the port-based chartmaker by a returning mariner. But how that could have applied to the graphic, and sometimes complex, danger markings is less clear. The most obvious way to insert details of a rock, reef or shoal would have been to add those to an existing chart. Back in port, the intermediary could then have let the chartmaker copy off the patterns of crosses or dots. Alternative transmission methods involving visual memory and two aural/oral stages seem far less practical.

It might have been expected that a sailor who was minded to gather and convey such information would have supplied details to a single chartmaker about several hazards in a particular area. But, Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated apart, there is little evidence of any cluster of local dangers being added at the same time, and the process seems instead to have been piecemeal.

Closely related to the above are the lighthouses and other devices designed both to signal danger and help mariners avoid them. The word ‘pharos’ was the medieval term for a lighthouse and about ten instances of faro have been noted in the portolan chart toponymy. 391 

K.2d. Fishermen

Related to the issue of what features could jeopardise a ship's safe passage, and reiterating how that would be a central concern for any medieval sailor, it is reasonable to expect that attempts would have been made, probably routinely, to seek information orally from local experts. I owe to Michael Barritt a suggestion, which has not apparently been clearly articulated before, about the potential role of fishermen as informants. In his own career and certainly in those of his predecessors as hydrographic surveyors, they would, as a matter of course, have consulted those with the best local knowledge. He cites the experience of Captain William Durban of Weazle, who, during his survey of the Skerki Bank in 1802, called in at Trapani, Sicily, where he embarked some local fishermen. On his return to the bank he almost immediately found its shoalest point, to which he gave its present name, Keith Reef. 392 

Without charts or other documentation, dependant on oral instructions when young and relying on memory thereafter, fishermen would have built up an invaluable store of practical knowledge about the names of natural features and the navigational dangers in their own area. If the local fishermen were the main source for the information about those hazards, it is certainly possible that, on occasions, they might have drawn the symbols directly onto a sailor’s chart.

If that suggestion is accepted, fisherman – various and anonymous – would have a real claim to be one, if not the main, source for information about the in-shore navigational dangers that form so important an element of the portolan charts' purpose and usefulness. If so, that contribution has hitherto been ignored. That Francesco BeccariFrancesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library) does not mention them on his chart of 1403 in the roll-call of those who contributed updated information for the charts – “masters, shipowners, skippers and pilots of the seas of Spain and those parts” – is unsurprising. 393  He was not a sailor and, as a chartmaker, would have received any information from such a source via an intermediary, possibly without realising how it had been obtained.

K.2e. Religion

Those on board a medieval vessel, whether mariners, merchants, soldiers, travellers or pilgrims, went in dread of the very real natural hazards they faced. These ranged from the vulnerability of their ships to weather events, hazards lurking offshore, or the threat from pirates, and this led naturally to prayer. 394  As Aaron J. Brody pointed out “Maritime religions were a discrete subset of the general religious beliefs and cultic practices of ancient Mediterranean societies, generated by the unique uncertainties and dangers faced while living and voyaging at sea”. 395 

In this context, promontories played a special part, with the charts aiding the mariners’ search for divine assistance. A number would have had a temple shrine visible from the sea but in addition, as Christer Westerdahl explained, promontories “were also dangerous, not only as cliffs to founder on in unfavourable winds, but often exceptionally so, since capes often mark a change in climatic conditions with conflicting winds, and expose seafarers to strong and sometimes fickle currents, sometimes at the same time”. 396 

Leaving geographical boundaries aside, what is likely to have been of greater relevance to sailors would have been those of saintly suzerainty, and the charts’ place-names would have enabled them to identify the appropriate saint for that locale, who could be asked to intercede in times of special danger. 397  After all, it was God who had the power to save or abandon the mariner when at sea, not the local lord.


Table of Contents


For brief summaries see the Conclusions


 

K.3. TOPONYMY

Coastal itineraries of the Mediterranean, in the form of simplified lists of adjacent places and features, sometimes noting the distance and direction from one to the next, long pre-date the portolan chart. The extent of ancient knowledge can be seen in the Classical periploi, and similar lists were certainly circulating in the Muslim world in the 10th century. 398 

Of the cartographic elements being considered in this section – principally, coastlines, offshore dangers, place-names and the treatment of islands – it is only with the toponymy that we can find documented antecedents. However, the handling of that element on the portolan charts is noticeably different from what can be found on other maps, whether earlier or contemporary.

Among the portolan charts’ many unique features is its omission of the usual positional dot for a place-name. This gave the draftsman flexibility in the placement of the toponyms. Even if some names needed to be located with a degree of precision, the intervening ones could be spread out evenly to aid readability. This would also have simplified the task for the chart copyist. Interestingly, that convention would be repeated in the London Underground MapHarry Beck’s much-imitated design of 1933 replaced traditional maps with a simplified diagram. This used eight directions only and ignored the actual distance between stations. It is argued here that it had much in common with the portolan charts, discussed later. 399 

So, while it was important that the toponyms appeared in the correct sequence, and could be memorised as such in a list, it was not felt that they needed to be realistically located. This imprecise positioning might endorse the contention here that the names had been memorised as a sequential list rather than, as in a portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes, being considered in relation to the size of the intervening distance from their neighbours.

For many mariners, detailed toponymic information may not have been essential, since most of the relevant names were probably known to them anyway. It was the sequence and position of named promontories that was crucial, less so those of ports and rivers. Toponymy’s value for a navigator would have been as a prompt for the memorised information he already held about a natural feature or port. Where the names must have been central was in relation to the oral transmission of routes, when narratives could be attached to them, perhaps forming ‘story maps’. 400 

Among those who would have benefited from the 2,000 or so place-names on a standard chart were non-sailors with a strong connection to the sea, particularly shipowners and merchants. But the portolan chart did not come into existence to service their needs and no features have been observed that would have been added specially for them 401  Nevertheless, the charts’ impressive body of littoral and island place-names, and the visible relationship of the various ports, would have been valued by the mercantile class, who would now have a better understanding of the overall dispositions, particularly when those related to the voyages of their own vessels. 402 

K.3a. The Carte Pisane’s toponymy compared to that of the portolani

In seeking to understand the relationships between, respectively, the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) and Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) (and particularly the first of those), various questions need to be addressed. How might that toponymic information have been gathered? Could either the chart or the written guide have been the primary source for the other? In other words, what might have been extracted from a chart for reuse in a text; or, alternatively, how could a chart’s toponymy have been populated, and the individual names positioned, using a text? The succession of places and features along the coast would surely have been absorbed by a mariner through experience, rather than being learnt from a portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes , and with the appearance and characteristics of each carefully filed away in memory. Passing from one harbour to the next could take a matter of hours, and, with nothing else to look at, there would have been plenty of time to record the visual details.

Against that, given that its toponymy is the only textual element on a functional chart, it is not unreasonable to assume that the place-names would have derived from a written source. In that scenario, a pilot guide, with its littoral itinerary, would be the obvious candidate. To test that, a comparative analysis was made of the place-names on the two portolani and the Carte Pisane. In the first place, little of value would have been learnt by considering, for example, places such as Barcelona, Dubrovnik or Sfax, since those would inevitably have been included. A more relevant comparison is one that focuses on the less common, even unique names. So, considering only toponymic incidence, rather than the erratic name forms – in other words treating the presence of a toponym merely as a measure of what was both known to, and sufficiently valued by, the respective compilers – the standard names were then removed from the analysis. 'Standard' is defined as those that appeared among the roughly 15% that were highlighted in red ink throughout the life of the portolan charts.

There were two further refinements. First, the analysis was restricted to the Mediterranean because the Atlantic and Black Sea coasts were not covered in all three of the documents being studied and, second, because the underlying toponymic analysis 403 had concerned itself with the mainland names only, the island names were also omitted. The resulting overlap between the toponymic lists in the Carte Pisane and the two portolani would then reveal the convergence or individuality of each, in a more meaningful way. 404 

The result showed significant differences in the three toponymic selections 405 [Powerpoint, Slide 25]. This was surprising, given that it is reasonable to have anticipated that anyone who sailed widely in the Mediterranean would have taken note of many, if not most, of the same features, whether those were ports, river estuaries, prominent capes and bays, landmarks that could be used to fix the vessel's position (such as churches, castles or mountains), or offshore islands.

From the percentages of the shared non-standard names it is clear that neither the Carte Pisane nor the other very early surviving charts were in any meaningful sense derived from the antecedent portolani texts. Probably decades of experimentation preceded the Carte Pisane but the two early portolani are unlikely to help us visualise the toponymy of such hypothetical precursors. Furthermore, turning to the two texts, no more than 60% of the Liber’s non-standard place-names can be found in Lo compasso – despite an attempt to match up the Liber’s Latin forms with the Italian versions in Lo compasso. 406  This reinforces the significant differences between the Liber’s names, which are listed in an anti-clockwise direction, compared to the clockwise preference of Lo compasso’s author. In its turn, the Carte Pisane’s debt to each of those texts is less than 45%. The dissimilarities of the littoral itineraries reflected in the toponymic sequences found on the Liber and Lo compasso on the one hand, and on the Carte Pisane on the other, suggest that at least three, unconnected, comprehensive toponymic surveys were made during or before the 13th century, unless future research found that all three might be interpreted as selections from a far more detailed lost original. 407  However, that seems unlikely because, whereas a portolan chart is restricted in the number of names that can be squeezed in, the same would not have applied to a text.

Further evidence that the portolani did not serve as inspiration for the charts comes from the context within which the toponymy was presented and the different purposes those imply. For the portolani, statements of the route from one harbour or headland to the next gave equal weight to distance and direction. Yet the charts, while respecting the coastal sequence (apart for occasional confusion along the Dalmatian shoreline), showed limited interest in the respective distances between the toponyms. Hence the portolani could not have derived their coastal itinerary from the charts because their imprecise placement of the toponyms meant that distances could not have been calculated from those.

Not only were there different origins for the place-names in the written narrative and the drawn chart but, in certain respects, their toponymy remained divergent over the centuries, with a number of names being unique to one or other format. 408 

K.3b. How were the toponymic lists in the early portolani compiled?

Leaving aside the coastlines of the north-east Atlantic and North Sea (whose addition to the charts only occurred after the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , 409 as well as the Black Sea, the two earliest surviving portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes and the Carte Pisane are more or less complete in their geographical coverage, without leaving any long, empty stretches.

Although this essay is mainly concerned with the medieval open-sea routes, most of the voyages at that time would have stayed close to the shore. This is relevant because a toponymic itinerary of such completeness could not have been compiled except by combining a number of coast-hugging journeys. No doubt some areas were politically out of bounds, and perhaps too dangerous to be visited directly. Those parts must have relied on hearsay or memories from easier times.

There is no indication that the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) was a multi-authored text. Nevertheless, it seems highly unlikely that its information was gathered afresh by a single individual, even if the apparently consistent treatment of its material might suggest that. After all, a continuous itinerary of the Mediterranean’s coastlines would cover more than 22,000 km.

Instead, in this case we appear to be looking at an editor able to merge invisibly his own direct experience with what was conveyed to him by others. Much of that detail, therefore, is likely to have come from one or more unidentified textual sources and/or, orally from his previous shipmates, fellow passengers and marine informants.

K.3c. Toponymic referents

The portolan charts’ mix of (often unstated) referents for their toponyms is probably unprecedented. This embraced a mélange of coastal and offshore features (even occasionally those well inland) such as gulfs, ports, capes, nearby islands, churches, castles, offshore dangers, rivers, lagoons, salt flats and mountains. 410  This ambiguity, helped by the lack of the standard cartographic black dot alongside each toponym, made it easier for the charts’ user, whether intentionally or not, to attach the name to whatever referent – perhaps more than one – he wished. Take agulones, for example, introduced just north of La Rochelle by the Pizzigani brothersThe Venetian chartmakers, Domenico and Francesco, left us a signed chart and an atlas from, respectively, 1367 and 1373 in 1373. It may indicate the port of L'Aiguillon, the Pointe de l'Aiguillon (a cape), or Anse de l’Aiguillon (an inlet). Or perhaps all three. It is equally possible that the meaning of a toponym itself might change over time. 411 

Unless, that is, the feature being referred to was specifically identified by means of a prefixed initial: c (capo, point, promontory or headland), g (gulf or bay), i (isla or island) or p (porto or punta – ambiguously, port or headland) – with rarer occurrences of mons (mountain when of significance for navigation), or words pointing to offshore reefs or shoals [see the previous section on ‘Navigational Dangers’]. Rivers might be denoted by a preceding r or a suffix fl. (fluvius). But frequently there was no epithet. Occasionally, the sequence includes the name of the region or even the country. The Carte Pisane Accepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) ’s toponomy for the North Sea coast, for example, lists in turn, and in a consistent lettering style: allamaigna, flandis, brugis, porto niua, gravalingue, friza (Germany, Flanders, Bruges, Nieuwpoort, Gravelines, Friesland). For those cases, and the instances where no clarifying term was provided, comprehension depended on the reader’s existing knowledge, backed up perhaps by orally conveyed interpretation from others.

For portolan chart toponymy to be properly understood by modern historians it often needs to be interpreted as indicative rather than precise, both as to its potentially dual or multiple meanings and its geographical placement, i.e., more of a label to jog memory than a unique identifier. This ambiguity also had its advantages for the copyist, since, by leaving the toponym with its multiple potential meanings, this simplified his work, and meant that – even where there was sufficient room – repetition could be avoided.

Maybe we should interpret those single names, which could, potentially, have had multiple references, as portmanteau terms for any or all of the local applications to which the sailor's knowledge or memory could be attached. And might such an ambiguous toponym have sometimes also highlighted an offshore danger, which was known to them if not to us, by the name of a nearby feature or settlement?

K.3d. Red names

The earliest surviving chart (the Carte Pisane Accepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) ) already reveals its debt to monastic illumination in its use of red ink to emphasise the names of the more significant ports; though we should not read into that any ecclesiastical involvement in the charts’ origin. Those red names would later constitute approximately one-sixth of the total, as more toponyms were ‘promoted’ to red. Surprisingly, a large number of chartmakers were apparently the first to do that in at least one instance. 412  That fits in with the parallel situation in which some of the place-names written in black also reflect the choice of a separate chartmaking school or even an individual.

About 90% of the red names on a portolan chart refer to ports, whereas the geometric structure of the pelagic courses had focused on the capes. This underlines the separate development of the charts’ graphic and textual elements. Natural features, however prominent, were almost never treated in red on the Carte Pisane. 413  This might seem to conflict with the sailors’ focus on headlands. Two possible reasons can be offered: that treating a cape and major port in the same way would have been confusing, and, further, that too much red – given that most promontory names brought with them a prefix, cauo de – would have diminished its effect. 414 

K.3e. Updating the names

Since we have no means of knowing how the charts’ toponymy might have developed between their inception (probably in the late 12th century) and the Carte Pisane Accepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) , and since the names in the two 13th-century portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open- sea (pelagic) routes are markedly different 415 we must look to the post-1270 developments on the charts themselves, for clues as to what might have gone before.

The place-names on a portolan chart were usually written with care. As a result, they are, for the most part, fully legible even on a chart where the smaller-than-usual scale reduces the lettering to minuscule proportions. Since they broadly adhere to a standard sequence, they can be readily documented and corralled into comparative lists. In addition, the general recognisability of the toponyms contrasts with the fluidity and subtlety of the coastal configurations. Moreover, despite what had earlier been assumed otherwise, portolan toponymy has proved to be highly dynamic. 416  For those reasons, their place-names have been the most closely studied feature on the charts.

The appearance in 2007 of the DVD accompanying Ramon Pujades’s Les cartes portolanes: la representació medieval d'una mar solcada, 417 offering enlargeable and rotatable scans of almost all portolan charts and atlases up to 1469, made possible the extensive comparative study of the toponymic component of charts produced by different individuals, schools and periods. The present author’s comprehensive listing of the mainland names from Dunkerque to Essaouira (Mogador ) indicates (among several other details) when each name was first noted on a dated or anonymous chart. 418  The impressive number of new entries – many hundreds added over the centuries to the initial 1,000 seen on the earliest charts of Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated – might lead to an assumption that there was a clear and continuing programme to update that element on a regular basis. 419  The fact that each of the identified chartmakers working up to 1408 apparently contributed at least one new mainland name to the total would appear to support that assumption. 420 

However, that observation provides a partially misleading impression of currency. A better guide to the development of portolan-chart toponymy can be found in the detailed analyses that have been published in recent decades. For example, in the case of the few settlements whose naming or foundation is firmly attested, it can be shown that it took an average of 75 years before their first appearance on a surviving portolan chart. 421 

More generally, it is abundantly clear that portolan chart toponymy was not systematically kept up to date. That nearly 800 mainland names were added to the initial 1,000 between the time of the first charts by Vesconte (1311 and 1313) and 1600 422 does not contradict the fact that very few of them were new toponyms, although some might have become newly relevant in the eyes of mariners. This might indicate that sailors had memorised much of that information anyway and were thus already aware of most of the omissions that were going to be rectified later. But that also meant that medieval mariners could not have relied on the topicality of the place-names in the way that modern assumptions might expect. If toponymic currency had been important to them, then surely they would have demanded regular updating before paying the considerable sum for a chart they would have considered to be at least partially obsolete. Even the sizeable group of Venetian sailor-chartmakers in the 15th century contributed little to the charts’ toponymy. 423 

Another consideration that should not be ignored relates to the mechanisms for conveying the details of new or altered toponyms to an individual chartmaker and, through subsequent imitation, to others. Clearly, some of the additional names could have been supplied directly to a chartmaker by a passing sailor from the locality concerned. But the innovations in question are spread across the entire Mediterranean and Black Sea so that explanation is inadequate. Instead, for a fresh name to be added to a chart three distinct stages might have been involved:

If that tentative reconstruction is correct it would mean that three oral/aural stages were involved, unless an educated member of the ship’s company had written the information down instead. This would have been a far from straightforward process. What was said by the local informant might be misheard. Even if remembered correctly, the same could happen when the toponym was passed, perhaps months later, to the chartmaker. He, in turn, might misunderstand or intentionally adapt what he had heard to suit his linguistic preferences. Finally the names that had been accepted were sold back to mariners in the form of a working portolan chart. Even if that suggested sequence refers to the updating of the toponymy on later charts, a similar procedure might well have played its part from the outset. It is worth remembering that the portolan-chart toponymy would have been fully up to date only at the time the very first charts were being constructed; thereafter, it was left to accidental, uncoordinated updating {this sentence added 26 February 2021}.

Francesco BeccariFrancesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library) is a notable exception to the general laissez-faire attitude of chartmakers towards toponymy. His sole surviving chart of 1403 is notable in many ways, one of them being its large number of new place-names. His statement on that chart that he had relied on a range of informants – ‘masters, shipowners, skippers and pilots’ – indicated that he actively sought to update his own toponymy. 424  That his additions were slow to be imitated by rival chartmakers is not untypical. Clearly chartmakers would have seen each other’s productions – shown to them by sailors no doubt – but they were apparently selective about which additional toponyms, if any, they would copy onto their own charts. This downgrading of the importance of place-names should be seen as both cause and effect of the erratic and usually delayed incorporation of new information onto the charts. 425 

Portolan-chart toponymy has served as the focus for many studies by cartographic historians seeking evidence for attributing unsigned works to a chartmaking school or individual. Further detailed comparative studies of the names on the Carte Pisane and its first successors might well help to clarify the different lineages there could have been in the period leading up to that first surviving chart.

The merchants and shipowners, who are likely to have relied on the charts for the names and location of ports and islands, seem not to have acted as a stimulus for toponymic updating. Perhaps, they were simply unaware of the charts’ limitations, or considered those to be insignificant.

It seems likely that the secondary importance attached to updating the toponymy through the long life of the portolan charts could well have applied at the time of their origin. As already suggested, the geometric diagram that was likely to have preceded the first recognisable chart would probably have restricted its initial toponymy to those features and places that had been selected as pelagic termini, meaning that what were considered to be less significant intervening toponyms would only have been added later as the portolan chart evolved. 426 


Table of Contents


For brief summaries see the Conclusions


 

K.4.   ILLUSTRATIONS AND COMMENTARY

Given that the portolan charts are popularly celebrated for the decorative excesses found on some examples, it may seem churlish to reduce this section to a few brief comments [Powerpoint, Slide 26]. But, while fully accepting that the highly-illustrated charts and atlases can be aesthetically pleasing, they add nothing to the study of portolan chart origins or to their history as a practical seafaring aid. After all, none of these adornments appeared until around sixty years after the time of the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . The distinction between austerity and adornment was summed up thus by the unknown author of the Genoese world map of 1457, which has a portolan chart at its core: “This is the true description of the world of the cosmographers, accommodated to the marine [chart], from which frivolous tales have been removed”. 427 

To summarise briefly the introduction of the various visual elements, the first to appear were the flags. Urban banners are first seen on the charts of Pietro VescontePietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated from around 1320 as well as on the undated Lucca chartDiscovered in 2000 in the city archives, this is visually very different from other charts from the 1st quarter of the 14th century (Archivio di Stato, Lucca, Fragmenta Codicum, Sala 40, Cornice 194/1) . For all their visual appeal, those were intended to convey important information about the town’s ownership. Could the ship expect a friendly or hostile reception? Unfortunately, the vexillology was seldom up to date and, as I wrote in 1987, “Many a Christian sailor would have ended up a galley slave had he relied on his chart to distinguish friend from foe.” 428 

Most of the other illustrative devices were introduced on portolan charts made in Palma, Majorca from 1330 onwards. The interior had been left blank on the earlier Italian charts, but that was now put to good effect for portraits of enthroned rulers, small stylised diagrams for towns, and so on. Those same Catalan charts often include text panels providing geographical or historical information. This was evidently aimed at educated landsmen rather than the sailors, who might still have been illiterate. That the 1375 Catalan Atlas references Marco Polo and Sir John Mandeville in the appended eastern half of the work (which is not based on maritime experience) emphasises the quite different source and purpose of that extension compred to the portolan chart which fills the western half.

Realistic views of Venice and Genoa appear on the 1367 Pizzigani chartThe Venetian chartmakers, Domenico and Francesco, left us a signed chart and an atlas from, respectively, 1367 and 1373, along with pictures of ships. A century afterwards, religious images were placed by Petrus Roselli (fl. 1447-69) in the tapering necks of his charts. 429 

The increased cost of those added features that had no relevance for navigation point away from shipboard use towards merchants’ offices or the homes of the wealthy, even rulers. Such adorned charts survive in vastly disproportionate numbers compared to the very rare working versions. 430  Virtually mass produced, those functional examples, which would have been standard equipment on board a ship, have almost entirely disappeared (except for a few scattered fragments retrieved from archival bindings) having presumably been worn out through use and then discarded. 431 


Table of Contents


For brief summaries see the Conclusions


 

L. ORALITY, LITERACY AND GRAPHICACY

 


 

L.1.  ORALITY AND THE PORTOLAN CHART

The combination of orality and memorisation is the key to understanding medieval navigation.

Maritime lore at the conjectured time of the first portolan chart (c.1270) was spoken, heard and assimilated, demonstrated and remembered, but not written down. As Joaquim Alves Gaspar summarised: “There is no doubt, whatsoever, that navigation prior to the chart era – both coastal and oceanic – was conducted on the basis of the knowledge and experience of pilots: about courses, distances, navigational dangers, prevailing winds, etc.” 432 

As a result, mariners must have carried in their heads three things: a memorised databank (made up of course instructions and marine lore generally); what might be termed an ‘imagebank’ (for recognition snapshots); and the equivalent of a video archive (for instance, when moving through the Aegean). Nor can the portolan chart itself be understood without accepting the hugely important role of orality in its origin and use. The wholly pragmatic, artisanal environment out of which we are claiming the chart emerged can only be appreciated with an orality-gaze, not a literary one. Indeed, it is hard to envisage any place in that process for the written word. 433  Since oral activity leaves no record, and we are arguing that there is no reason to expect that technical navigational matters would have been described in documents that might have subsequently been lost, that leaves us with virtually no tangible evidence.

Born out of the shared memories of experienced mariners, the portolan charts’ later development would continue to be characterised by similar types of collaboration, which surely point to useful analogies for the charts’ prehistory period prior to the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . There must have been numerous unrecorded informants who kept the charts’ toponymy (erratically) refreshed, and their use at sea must always have heavily depended on the oral/aural exchange of ancillary information, whether descriptive or explanatory, vital for navigation.

As a parallel instance, it is possible to envisage a shipwright setting down his lifetime’s knowledge in a text illustrated with measurements and diagrams, even if that step seems not to have been taken until after medieval times. But, however accurate and detailed the descriptions of those construction processes might have been, that would not, on its own, have turned an apprentice into a master. Carefully memorised experience and finely-tuned senses would have been essential. How much more would such considerations have applied to those navigating the featureless waters of the open Mediterranean, faced with innumerable uncertainties, requiring repeated decisions.

There must have been a number of reasons that a portolan chart was evidently considered an important, if not essential, aid. Its scaled geometry of the Mediterranean and Black Sea must have given a major advantage to pelagic sailors. Unprecedentedly realistic (and above all eminently usable), it provided for the first time a picture that, in its completeness and veracity would have been beyond the experience of any single mariner. Nevertheless, that could only have been part of what a pilot required. However useful the chart might have been for open-sea sailing, it would not have been sufficient on its own. In some respects it was little more than a prop or backdrop for learnt or memorised navigational lore. Access to the orally-transmitted, memorised information and images that the medieval sailor depended upon is impossible, since those, by definition, could not have left any trace. Which is why it is so important to attempt a reconstruction of the knowledge that might have been in their heads.

L.1a. What needed to be explained orally for the charts’ effective use?

Memory and orality must have played a large part in the use of the portolan charts. The interrelationships between the two are complex: what was remembered could be passed on orally, to create a new memory in someone else. Oral exchanges might have been involved even before the voyage began, with input from harbour-masters and others in relation to the pelagic course to be followed at departure and from fishermen for local navigational details. 434 

Two specific types of memorised information can be distinguished, even if they sometimes merge or reinforce one another:

Narrative – the content of memorised instructions that could be passed on orally. The obvious example would be the directions for a particular course and the distance or time involved

Experience – what was held as visual memory, in the form of the equivalents of a personal photograph album (‘imagebank’) and video records. The ability to recall and recognise coastal features would have complemented the factual narrative of a reimagined voyage

Whoever purchased an early chart could never have encountered anything like it before, even if (which is unlikely) they had previously seen a map of any kind. The chart’s form and cartographic language were original. Some of its conventions might have been assimilated easily, but the symbols denoting dangers for example, which seem to be a portolan-chart invention, were not intuitive. The red dots for shallows could equally have indicated sandbars or mudbanks. In other words, the portolan chart was incomplete, and of much reduced usefulness, without exegesis. They were not designed for unassisted novices. For these reasons, instructions for the charts' use must have been conveyed orally: first from the seller to the sailor when purchasing his first chart, and then from him to his colleagues, including no doubt the ship’s boy as part of his apprenticeship (as described by Benedetto Cotrugli). 435  Additionally, by building up a store of memorised knowledge over repeated voyages, the mariner would be able to attach his remembered experiences to the chart’s littoral toponymic sequence.

Today, we take for granted that a map will have an explanatory key but the portolan charts remained mute throughout their long life. The following lists describe the types of information that, in the first group, were present on the chart but required elucidation, and, in the second, were supplementary to what was provided by the chart, and hence had to be supplied by the user. It is unlikely that either list will be complete.

L.1a.1. Aspects of the charts’ information that required explanation:

Direction lines: The charts’ most noticeable feature is what might at first glance look like a jumble of intersecting lines. However, those can soon be visually unscrambled and a pattern identified: namely intersection points set at regular intervals around one or a pair of (usually) ‘hidden’ circles. It would need to be explained that the network offered up to 32 different directions and that the user should search nearby for the most relevant one. What any particular line represented had to be learnt. For that, colour-coding made recognition easier: black for the eight primary directions (north, north-east, east, etc.), green for the next eight (e.g. north north-east, east north-east) and red for the final sixteen (north by east, north-east by north) [Powerpoint, Slide 15]. North, South, East or West might be indicated, by some kind of pointer for north and a cross device for east. Initials, usually no more than eight, might be used to denote the more prominent of the traditional ‘winds’. 436  In order for the novice to orientate himself in relation to the chart, therefore, he would first need to know which line pointed north (or rather south, since that seems to have been the orientation of the earliest charts). He then had to identify which direction line corresponded with one of the sixteen named winds he was told to look for [that figure could be doubled by the addition of references such as ‘between wind A and wind B’].

Scale: The value of the ‘mile’ represented in the distance scale is never stated on the portolan charts (as it would be on later marine charts). Indeed, although the decimal system was already present on the earliest charts, the users of the Carte PisaneAccepted as the oldest surviving portolan chart, c .1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) would have had to be told that the smallest divisions represented five miles not ten. 437  However, it seems likely that the charts’ users would instead have estimated the duration of a course in terms of how many multiples it was of a few clearly remembered standard distances (perhaps between their home port and others), measured off the chart with their hand. 438 

Winds: If the eight named winds that were used for the mental compass were indicated at all it was by means of an initial letter placed beside a primary wind. The full names would need to be explained

Dangers: The signs for shoals, rocks, and their various combinations have already been discussed. 439  Because they were unprecedented and no key was provided, they would certainly have required explanation. 440  Besides that, the initial, highly simplified symbols seen on the earliest charts were to develop by 1400 into something quite different, thus involving some re-learning. 441  Even though some of the symbols survived into modern times, we cannot now be sure of the exact meaning that the earliest charts were conveying. Identification also presented problems. Few of the offshore hazards have names alongside and when toponyms were provided they would sometimes be transferred into the main coastal sequence nearby, as if they were land features. Even if the danger was placed with some precision, its specific threat and perhaps its name would need to have been explained.

Coastlines: It might be expected that coastal outlines would have conveyed strict reality, at least to the extent that the map’s scale allowed. However, the portolan charts’ creators had no such concerns. What lay between the headlands was of marginal importance for navigation, so the intervening stretches were usually simplified into regular patterns. The capes themselves would often be drawn in a stylistic manner, sometimes reflecting that chartmaker’s distinctive signature. The chart’s user would have soon become aware that little could be learnt about his ship’s position in terms of recognising particular coastal features, although subtle variations in the depiction of the shoreline might hint at different general types. 442 

Rivers: In a similar way, the portolan chart’s user would come to realise that the great majority of river mouths were depicted in an identical fashion, with only a handful of major outlets enlarged, and the four main deltas in the Mediterranean and Black seas given individual treatment. So, when moving along an unknown shoreline, the charts would do little to aid recognition there either. 443 

Toponyms: It would be reasonable to assume that this element provided the user with simple, precise information. However, a number of the toponyms had ambiguous or portmanteau meanings, leaving the reference unclear unless there was a prefixed initial to distinguish a cape, bay, port, island etc., of the same name. 444  Nevertheless, the charts’ toponymy must have served as a mnemonic device, in the form of labels on which to hang not just referents but also detailed memories, both of instructions received and stored images from past voyages.

Geopolitics: Graphic devices identifying ownership of the more significant ports are first seen on Italian charts of about 1320. Since these town flags include some of the earliest instances of recorded vexillology – which means that they might not have been generally recognised – their significance would need to have been orally explained. 445  In addition, those armorial pennants were not a reliable guide to geopolitical reality because the information they conveyed was often out of date. Sailors must have relied instead on verbal exchanges in port if they were to be kept apprised of changes of suzerainty. Likely questions would have been: what reception could be expected if they landed at certain places; were pirates operating in the area and if so how best could they be avoided?

Other illustrative elements: The embellishments introduced on Catalan charts from about 1330 onwards, such as ethnographic illustrations, enthroned rulers and small stylised diagrams for towns, might have needed to be explained but they have no relevance for the earliest surviving charts or, therefore, the origin question.

 

L.1a.2. Information not provided by the charts but necessary for navigation:

Leaving aside the sea signs listed earlier, 446 which could not have been conveyed on a chart, there are some indicators that a portolan chart might have included, for example:

Anchorages: On occasions, a sailor would need to know the location of the nearest protected anchorage to ride out an impending storm. Perhaps the charts’ modest scale made that impracticable but in some cases a small anchor symbol, of the type introduced onto later charts, could have been squeezed in. Given the charts’ practicality and the innovative approach of a number of early chartmakers, there was probably a good reason for this omission.

Approaching harbour: This can be the most challenging part of a voyage but the charts do not provide any pilotage details, such as buoys, lights, leading lines and so on. Unless a local pilot was taken on, or any brief comments there might be in a portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes were accessible to a literate crewman, they would have had to rely on remembered experience. It would have been possible to include enlarged details of a few of the more hazardous harbour approaches, placed inland – and later marine charts did just that. However, as the situation would often change, with silted channels or shifting mud or sand, the omission of this information from the charts had the benefit of saving them from becoming redundant.

Lighthouses: The absence of those is surprising, given their importance as both warning and location devices 447 

Provisions: Likewise, it might have seemed helpful to have included a code for sources of fresh water and places to re-provision, particularly less obvious ones. Again, shifting circumstances would have rendered some of that information obsolete.

Routes: There must have been preferred routes through the Aegean to the Dardanelles and on to the entrance to the Black Sea, perhaps with different tracks for those entering from the west or east. If so, might a pair of simple lines not have indicated those? Evidently, no doubt for good reasons (variable winds, changing political allegiance?), this was never done.

Wrecks: The charts do not specifically warn of the presence of a wreck, unless any of the black crosses for rocks and reefs could have been interpreted in that way. However, most of those would have already been included by implication in the specific hazard warnings, since it would have probably have been on one of those features that the ship had foundered.

L.1b. Orally transmitted pelagic knowledge

Because a sailor’s training was purely practical, involving instruction, imitation and criticism, it is not surprising that there was no textual guide to that process in the Middle Ages and that details of actual pelagic courses had to come from memory and oral instruction.

An earlier section of this essay had focused on the brain and spatial memory. 448  It is worth considering further the capacity of memories that had been developed from infancy. M.R. O’Connor noted that “by six, children show a strong positive relationship between hippocampal volume and their episodic memory – the bigger the volume, the greater the ability to recall details of an event.” 449  Medieval pilots would probably have started their life at sea as boys and the voyages they undertook would have been held in memory in the form of a succession of events.

Information stored in the head of a sailor whose safety and even life depended on it, would have been far more secure than any simple diagram or scribbled note. As a result, it was hardly likely that the oral tradition would have been rendered entirely obsolete by either the magnetic compass or the portolan chart. The holistic memory of a single long-distance course might have extended to a number of pages, had the full detail been written down. Such memorised records of voyages would have called upon several of the navigator’s senses as well, with the verbal instructions and personal video record of previous experience being only the most obvious. Turning some of that disparate information into a written pilot guide was not realised until the printed versions of later centuries, when artificial aids had rendered most of the memorised information redundant.

Though possibly not all of it. Perhaps some mariners took heed of Socrates’s warning from the 5th century BCE:

In fact, it [writing] will introduce forgetfulness into the soul of those who learn it: they will not practice using their memory because they will put their trust in writing, which is external and depends on signs that belong to others, instead of trying to remember from the inside, completely on their own. 450 

Which view was restated this century by the cultural ecologist and philosopher, David Abram:

“The alphabet and alphabetic literacy does not cause our human estrangement from the more than human natural surroundings. But it makes it possible in a way that is simply not possible for traditionally oral indigenous people who are so deeply embedded in the particular landscape that they inhabit, and they are practising relationship all the time with … the winds and the weather powers … Alphabetic writing makes possible a forgetting of that larger field of active agencies”. 451 

Sailors who were being taught the relevant details of a particular route – and they might have been apprentices, having it beaten into them – would have absorbed a mass of varied information. Among the more important was the knowledge needed to leave harbour safely, before turning to pick up the wind or compass direction required for the first of what might be several distinct legs of that voyage. For each subsequent stage, due note had to be taken of any known hazards that had to be actively avoided on the way to the next waymark, which needed to be recognised and perhaps passed at a specified distance. Gauging the passage of time and estimating distance were essential skills, along with the ability to ‘read’ the wind compass and use the available astronomical aids.

It could be expected that a single individual regularly repeating a particular course might have been able to refine its details and thus, gradually over time, arrive more precisely at his destination. But if this was due less to improvement in the sailing directions and more to enhanced sensory and memorised skill, then it would not necessarily have led to any refinement of the guidance that could be passed on to others. In evolutionary terms it would be irrelevant because it would not have left its mark on the collective memory. That is why this thesis argues that one of the seeds out of which the portolan chart grew would have been the realisation that the individualistic and disjointed pelagic course memories could be made more accurate only through a collaborative process, using a graphic medium to combine them into a single permanent record.


Table of Contents


For brief summaries see the Conclusions


 

L.2.   TWO MODERN COMPARISONS


L.2a. London’s Black Cab drivers

It may be instructive to consider similarities between what was required mentally of a medieval pelagic sailor and the experience of London’s Black Cab drivers, whose brain functions have already been discussed. 452  In each case there was a clear motivation to learning: future personal safety for the ship’s boy and, for the trainee cab driver, the realisation that failure would deny entry to a desirable independent career.

The drivers’ training and daily activity have been closely studied, providing the detailed evidence that is entirely lacking in the medieval case. Just as the cab driver must remember the name of every street on his or her planned route as well as the turnings off it, so the open-sea sailor had to retain a wide range of remembered or learnt details. All would have been absorbed orally, and discussed in a port tavern or on the dockside – the mariners’ bourse or free navigational exchange. Until a few decades ago, the Cabmens’ shelters served a comparable purpose in London. 453 

There is, of course, one major distinction in that the London cab drivers memorised an existing street plan, whereas Mediterranean sailors had to build up their mental map from scratch. Yet each had to keep their knowledge up to date, in ways that echo one another. A comparative list of those aspects which needed to be refreshed might look like this:

Cab drivers: traffic problems (temporary or permanent), accidents, road closures and diversions, alterations to one-way systems, or other reasons to alter a usual route

Sailors: ports now open or closed, new wrecks, changes to the route into port, new customs regulations [all orally communicated in port], piratical activity, new sandbanks or mud bars

Recent research is revealing the reinforcing effect of a well-used memory, finding that:

the more time the London Black Cab drivers spent on the job, the more the hippocampus changes structurally to accommodate the large amount of navigational experience … Drivers who spent more than forty years in a taxi had more developed hippocampi than those just starting out ... Conversely, they found that using a GPS excessively might to lead to atrophy in the hippocampus as a person ages. 454

It is surely safe to assume that with both medieval pilots and Black Cab drivers the expansion of their knowledge was never ending.

L.2b. The London Underground Map

What follows may reasonably be considered a digression, but it is offered here as a theoretical analysis to highlight some fundamental cartographic principles and promptings. These unite across many centuries what might otherwise be assumed to be wholly unrelated map types.

The second modern parallel – the London Underground Map – demonstrates remarkable underlying similarities with the portolan charts, not least around the issue of orality. 455  Each displays a ground-breaking design placed over a simplified structure, and each requires orally-transferred and memorised information for it to be used to the full. As Catherine Delano-Smith noted: ‘Diagrammatic maps are created specifically to provide an answer for those who know what the question is’. 456  We might extend that to a parallel statement: 'A diagrammatic map answers the questions that need answering’.

The creator of the Underground Map, Harry Beck, had previously been an engineering draftsman for the Underground Electric Railways Company of London. In 1931, he took the existing, traditional map, and extracted its salient features. He then arbitrarily straightened out the railway lines so that they ran in one of the eight main compass directions, and placed the sequence of stations and interchanges along those lines evenly, with limited regard to the actual length of the intervening distances. Thus he took a normal map and turned it into a highly simplified topological structure, a diagram or cartogram, which massively distorted geographical reality. By doing so he was able to offer the user easy, speedy, and unambiguous comprehension – with, like the portolan charts – almost no textual explanation 457 [Powerpoint, Slide 27].

There are several other similarities between these two clearly unconnected cartographic productions. In the first place, they shared the same principal concern: namely, the beginning and end of a voyage or journey, and the points in between where action was required. In each case, everything considered inessential for the map’s practical purposes was excluded, and geometric accuracy was ignored except where it mattered. Both resort to generalisation and intentional distortion when it furthered their aims. The earliest charts omitted inland features; Beck’s map ignored everything above ground. Both used colour-coding: on the charts, for islands, important places or compass directions; on the Underground Map, for the different lines. Codes conveyed hierarchies, whether by means of red names for significant ports, or to highlight the Underground stations where two or more lines met. The innovative symbols on the charts for the natural dangers threatening ships do not have a direct parallel in Beck’s schema, but the later addition of a logo for stations with non-step access is not wholly unrelated.

Visitors using today’s enlarged version of Beck’s design have no difficulty in ‘navigating’ the network, if all they need to know is where to get on the train, whether and when to change lines, where to get off and perhaps which zones are involved (in case that affects their fare). The map is clear about all those points. However, Londoners, who may have much of the network stored in their heads, supplement the map with their own memorised experience and the oral advice of others. They may, for example, need to know which interchanges are long and complicated, where (for the less mobile and those with luggage) there are stairs alone (no lifts or escalators). They are also aware how long the journey might take, given that the suburban stations are, in reality, much further apart than indicated on the map. For Beck, actual distance and direction, along with journey time, took second place to the requirements of a harmonious design.

Daily commuters (on crowded trains) need further, more detailed information: which carriage will be nearest the exit at the destination station, and on which side will the doors open. Thus, for the experienced user, just as for the sailor with his portolan chart, a combination of map and memory are required. 458  Having lived in London for many years, I would be lost, like everybody else, without the descendant of Beck’s map.

A single conceptual leap produced Beck’s map. For the portolan chart, at least as claimed here, there would have been successive stages: first, memorised single pelagic courses; then the gradual building up of those into a network; third, a graphic version of that network, and finally the addition of coastlines and toponyms. However, that was a process fuelled by continued collaborative inspiration, in contrast to Beck’s individual creation.

Neither of those productions had been previously imagined and so neither had been requested. Yet, once available, each was widely distributed and would subsequently become an indispensable aid for travellers: for four centuries in the case of the portolan chart and almost 90 years (so far) with Beck’s map.

I argue later against an assumed mercantile trigger for the invention of the portolan chart 459 and also queried the contention that its origin was dependent on the magnetised needle. 460  Instead it is proposed here that the chart’s inception could have happened at any time. For its part, the London Underground Map, rather than being commissioned or linked to any evident social or economic impulse, was a purely personal project, submitted to the Underground management at the suggestion of friends. Indeed, the company rejected it at first as being ‘too revolutionary’. 461  When it was published in 1933, following a re-submission, it was an instant success. The modest improvements and additions that Beck made to subsequent reissues presumably reflect the suggestions of passengers; in a similar way, feedback from sailors must have been the prompt for the introduction of a few new features into the portolan charts (and certainly the hundreds of added toponyms).

It is clearly appropriate in many cases for market forces or external events to provide the best explanation of the actions of individuals. But can we not allow the possibility of human agency, of an event explicable only in terms of exceptional individuals, working to their own rhythm? And could that not be applied equally to Beck for his Underground Map and to the unknown sailor(s) who conjured up the portolan chart without the help of any precedent?


Table of Contents


For brief summaries see the Conclusions


 

L.3.   LITERACY OR ILLITERACY?


L.3a. Would medieval sailors have been literate?

Given that the carefully written place-names are such a prominent feature, it is natural to assume [as I had done myself] that the charts must have been designed for literate sailors. Yet that does not necessarily follow, since it seems clear that few of the sailors responsible for guiding a ship at that time would have been able to read, even if some of the other crew members might have been literate. Why would navigators have had need of Latin? And why would the vernacular literacy, which was only just beginning in the 13th century, have dealt with artisanal issues?

Part of the reason that we do not hear the sailors’ stories, and hence have been left in the dark about the early history of the portolan charts, may stem from the fact that most of their users could neither read nor write. Hence the little we can learn about the early charts and their shipboard functions has come from literate passengers not mariners. A number of accounts survive from pilgrims, as well as participants in the crusades, but they offer few insights into navigational practice. 462 

There is a perception among some historians that illiterate sailors (or possibly even literate ones) would not have been able to create the portolan charts, largely because of their lack of education. Being unlettered is sometimes seen, even if unconsciously, as an indicator of lower intelligence. If so, that would be repeating the mistake of those European explorers who dismissed the knowledge and ability of the ‘savage’ peoples they encountered. Only later did it become clear that their indigenous informants often possessed a notably superior understanding of their own environment and, in the case of the sea, how to get around in it, than did the formally-educated Westerners. In the context of the portolan charts it can reasonably be suggested that the intellects responsible for devising the chart, collecting and selecting its content, and later adding further elements, were highly developed in practical ways, albeit unconnected to book learning.

In relation to textual support for historical argument (or indeed the lack of it) there is a useful parallel with the shipbuilders, who would have been close neighbours of the chartmakers in a port. The oldest known treatise on that subject was not written until about 1436 by Michael of Rhodes, and even then it was only the state-run establishments that used paper records at all. 463 

A further relevant parallel can be found in construction plans. If the cathedral builders, for instance, had made preliminary plans, these have not survived. The well-known sketchbook of Villard de Honnecourt (c.1225-35), includes many architectural drawings but, rather than being building designs, it is now suggested that they “were deliberately simplistic and abstracted to serve as coded mnemonic devices for architects who were initiated into the relevant oral tradition”. 464  Describing the situation in England, T.D. Sutton cites the paucity of examples of plans attached to builders’ contracts before 1500 (the earliest is 1380). In a familiar echo of the situation with portolan charts, the two early instances of an actual working plan survived only because their vellum was repurposed in a book binding. 465 

A final example contrasts the largely text-free portolan charts with a noticeably different travellers’ map, the cheaply-printed ‘Rom Weg’ map designed for the use of pilgrims going to Rome for the Holy Year of 1500. This included its own separate explanation sheet. 466  Clearly, the expected users in those two cases had different levels of anticipated literacy.

L.3b. In what way could the written word have contributed to medieval navigation?

Assertion: Even if some medieval sailors were literate, the inexperienced among them could not have found in the portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes the knowledge needed for navigation.

Around 1200, few sailors would have been able to read. No doubt there were literate landsmen on board a substantial ship – they would be needed for dealing with mercantile matters, for example – but it is highly unlikely that they would have been responsible for navigation planning or for those decisions that had to be taken at sea.

It is improbable that medieval pilots would have learnt the position of the stars from a book. Or even from a diagram, since, when they were using constellations for navigation, by definition they would have taken advantage of the genuine article above them. Where there might have been a need for written instructions was in the predicting of tides along the Atlantic; though that was not relevant for the Mediterranean coasts. Called ‘Establishment of the port’, it allowed the time of high water to be calculated according to the compass bearing of the full and new moons. 467  Yet that information was presented for sailors, not in the form of a text, but as a diagram, a simplified map, or a calendar like those in the Catalan AtlasActually a sequence of six panels, two of which cover the area of the usual portolan chart and two others extend east to make this a world chart, c.1375 (Paris, Bibliothèque nationale de France, Manuscrits, MS. Esp. 30) and later portolan atlases.

It might conceivably be the case that illiteracy could even have offered advantages for a medieval mariner, since mental space that might otherwise have been occupied by remembered texts could be freed up for conserving his experience instead. 468 

L.3c. What textual information was included on the charts and what omitted?

It may be a useful exercise to divide up the elements that make up the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) – our only guide, however approximate, to the likely appearance of its lost antecedents – between those that were squarely aimed at literate users and those which could have been understood by non-lettered sailors.

L.3c.1. Information aimed at literate users

Viewed in that light, the Carte Pisane made only slight demands on its literate users. It includes just three textual elements: toponymy, the names of the eight main winds, and a single hazard warning. The pervasive toponymy is the obvious case apparently demanding reading skills. However, we will consider that, counter-intuitively, in the next, combined category instead. That leaves the repeated warning of a lone offshore danger, a supposed rock to the west of the Ionian Islands, signalled dramatically by the repeated word Guardate [watch out]. It is not worth dwelling on that here but this is clearly written in the same ink and with the distinctive capital G and lower-case d found elsewhere over the chart. In other words, it is not an addition by a user. As it happens, there is no rock near there, nor could there be, because of the depth of water. So, an unexplained anomaly. 469 

The other significant textual element – although found only on some later portolan charts – are discursive historical and geographical legends. Those are generally restricted to Catalan charts from 1330 onwards and, in particular, to the more ornate versions designed for landsmen. 470  It is notable that neither there or indeed elsewhere do the charts provide any written guidance about their own use.

Had the early charts included written passages, that would have necessitated choosing a particular language. Would it have been Latin (highly unlikely) or one of the emerging vernacular languages, such as Catalan or an Italian dialect? If so, that could have reduced the charts’ relevance to those besides the chartmakers’ countrymen – since we know they were sold all over the Mediterranean. 471  In that situation, the Greek sailors in the Aegean would have needed charts that used their own alphabet for the toponymy, yet the earliest known examples of those date from the 17th century. 472 

L.3c.2. Information that could be understood by non-literate users

It may seem provocative to suggest that this category could have included the main textual component of the functioning portolan chart, namely its toponymy. Surely this element would have been accessible only to literate sailors? Kevin Sheehan’s reconstruction of a portolan chart found that the place-names, along with the hydrography, were the most time-consuming parts of the drafting process. 473  Since this meant they would be expensive for copyist and purchaser alike, why would so many chartmakers have taken the trouble to add to the initial place-name list unless those who bought and used the charts were able to appreciate that element?

That is a very reasonable argument; however there is another possibility. It is likely that the illiterate sailor would have been habituated to committing to memory what he could not read, just as all Mediterranean mariners had needed to memorise sequences of coastal names until the portolan charts laid them out conveniently. After all, an illiterate seaman had an equal need to know those names and hang associations on them. If it became necessary, a literate crewman could have read them out to him. On the other hand, once the chart was available, the literate chart-owning sailor would have been provided with a helpful alternative to memorising those long lists of toponyms [there are around 2,000 on a typical chart]. Likewise, how many of today’s regular users of the London Underground trouble to memorise the sequence of all 270 stations on the eleven inter-connecting lines, when they have ready access to the map?

There is another aspect that may have played a part. The seamen gathered in the Italian quayside taverns would have been speaking in a babel of languages. Faced with these various dialects, it seems that there must have been a tacit agreement that linguistic differences should be submerged in a ‘lingua franca’, which allowed broadly standard toponymic forms to be widely shared. The non-literate sailor could have learnt to recognise the shapes of names and their sequence, or to home in on the more important places that had been helpfully highlighted in red. When that conformity was set aside, as, for example, with the idiosyncratic (sometimes unrecognisable) readings on the 1492 chart of the Portuguese, Jorge de Aguiar, 474 the convenience of approximate toponymic standardisation becomes clear.

The inclusion of toponyms on the portolan chart certainly meant that the copyists had to be literate but it cannot be assumed that all the users were as well. Which also begs the question of whether the creators of the portolan charts’ initial hydrography would have needed to be able to read and write. What disadvantage would they have suffered if they could not? Nor is it certain that the initial gathering of the place-names, or the subsequent additions to those, had necessarily been recorded in writing. They could as well have been orally transmitted by illiterate informants.

Which side of the orality/literacy fence should we place the mnemonic island shapes, first introduced – particularly for the Aegean and Dalmatian islands – in the work of the Vescontes Pietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated and Angelino DulcetiAngelino Dalorto or Dulceti was a Genoese who worked in Palma, Majorca, leaving us dated charts of 1330 and 1339. His were the first to introduce inland and illustrative details (1311–c.40), and sometimes continued thereafter for centuries? 475  Each island or islet remains clearly named on those charts, but it is more likely that the signature shape provided for each entity was intended as a more accessible alternative form of recognition for illiterate sailors, who could associate the outline with its remembered coastal profiles and toponym. That group might have included, for example, literate Greek sailors if they could not understand roman script. In a similar way, the flags signalling ownership of the port concerned could have been recognised by any sailor, as a substitute for a written label.

L.3d. Were the charts initially designed with illiterate users in mind?

I take here a different line from Ramon Pujades, who considered that “the nautical chart is not a mute object but rather a map laden with writing” and that “such a valuable instrument of written culture as a nautical chart, which would have been practically useless in the hands of an illiterate…” 476  Instead, as has been shown here, almost nothing on a functional chart demanded literacy. The absence of explanatory text, and hence the need for oral instruction instead, meant that navigators just continued what they had been doing previously. The same oral process would have been employed for training young sailors in the use of the charts and for the exchange of information about navigational issues when at sea. From this we can infer that the lack of specific guidance for literate users, or indeed on navigational topics in general, was an intentional decision by the chart’s creators. Given the charts’ multi-lingual usership, and the previous comments about the lack of literacy, it is worth considering the possibility that the chart’s creators might have sought to overcome those difficulties by intentionally producing a ‘non-linguistic’ navigation aid.

There is supporting evidence of this from certain non-navigational details found on the earliest charts. Examples that can be cited are the town symbols along the Danube on the Cortona chart Based on its archaic appearance, this is considered to be the second oldest surviving portolan chart after the Carte Pisane, dating from the beginning of the 14th century or even earlier. It was first described in 1957 (Biblioteca dell'Accademia Etrusca di Cortona, Port. 105) chart, the church vignettes and a large rose on the Avignon chartA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html , and the strange city signs on the one preserved in the Lucca chartDiscovered in 2000 in the city archives, this is visually very different from other charts from the 1st quarter of the 14th century (Archivio di Stato, Lucca, Fragmenta Codicum, Sala 40, Cornice 194/1) . What is noticeable is that none of those iconographic details is labelled, which meant that the interpretation would have had to be conveyed orally, leaving historians to speculate about their meaning.

Those who are convinced about the part that the written word would have played in the portolan charts’ origin must provide evidence for that, not assume it.


Table of Contents


For brief summaries see the Conclusions


 

L.4.   GRAPHICACY


L.4a. The necessary graphical skills

What mental faculties were required to use a chart? By focusing on literacy and illiteracy, we are in danger of missing an aspect of potentially greater importance: graphicacy. This has been defined as “the communication of spatial information that cannot be conveyed adequately by verbal or numerical means”, inter alia, citing maps and plans. 477  Graphicacy is of direct relevance for both the charts’ creation and the use made of them, and specifically for the understanding of the cartographic conventions it introduced.

To reconstruct the world into which the portolan chart emerged we need to borrow the skills of a historical novelist. In particular we have to do two things: first, forget every map or, more particularly, satellite image we have seen and, second, accept that anyone around 1200, if they were concerned about the nature of the wider world, would have had to rely on formalised maps with little pretension to Euclidian accuracy. On land, it would have been hard for most people in that period to envisage an area greater than their own locality, or a particular itinerary they had followed. Larger extents could not have been validated by experience. Those who studied the maps which geographers had concocted of the world and its regions could do no more than choose from one of those alternatives.

But at sea the situation was fundamentally different. If we ask how did, or how could, a medieval sailor have envisaged the Mediterranean, a possible answer, if an unexpected one, would be because he had, to some extent, already done so. There would have been many mariners who had sailed, if not everywhere, at least to the far corners of the Mediterranean. And, by combining their memories of past voyages, they would have built up their own rough-and-ready mental outline map of the salient points around the mainland coasts, along with the interconnecting islands.

When our hypothetical experienced seaman first set eyes on a portolan chart, and once the salient features were pointed out to him, with the toponyms read out for him if he was illiterate, how long is it likely to have taken for him to match the coastal or island outlines to his mental map and pictorial memory? The only difficulty, and no doubt a real one, would have involved him translating the 3-D pictures of coastal profiles he held in his head into the two-dimensional outlines on the chart.

If we hope to understand the nascent portolan chart I suggest that we need to move away from treating it, first and foremost, as a cartographical production. This essay asserts that the cartography came later; it did not inform the initial chart’s creation as a graphical diagram or a scaled outline plan. 478  The portolan chart’s experiential basis, compared to the theoretical or literary constructs of the time, would have been bewildering for those who did not share the truths it revealed: in other words, all except those pilots with the graphicacy skills to ‘read’ the portolan chart, by interpreting new conventions and symbols, aided by an oral explanation of the chart’s main features.

It is unlikely, when a monastic geographer or a cosmographer saw their first portolan chart, that they would have thought it an improvement – until, that is, it was explained to them by a mariner. Only a navigator could have understood the outlines they were seeing and been able to endorse the chart’s veracity; and only their successors could have alerted the early chartmakers to its deficiencies, most particularly the mis-sizing of the Adriatic Sea.

Thus the very reason that the portolan charts would have flummoxed non-nautical viewers, because of their unprecedented appearance and conventions, probably explains why their intended users accepted them so readily, as testified by the charts’ wide reach and long survival.


Table of Contents


For brief summaries see the Conclusions


 

M. THE CHARTS’ FUNCTIONS

 


 

M.1.  THE VARIED PURPOSES OF THE PORTOLAN CHARTS AND HOW THEY WERE USED

Assertions:
The charts were only devised because they were better than pilots’ memorised knowledge.

There was no intention to create a comprehensive and fully accurate survey but instead to provide a functional tool for navigators to supplement their experience, not make it redundant.

Because there is no sign of any theoretical dimension to the functional portolan chart, we can safely assume that each of its features was included for a specific reason. As a test, try to find anything that could be removed from the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) without compromising its purposes.

There are few contemporary reports of how a portolan chart was employed in practice at sea, and none prior to the mid-14th century. 479  Written references to their shipboard use are unlikely to have been first-hand anyway. As expected, the few accounts come from landsmen observers or those who passed on information from mariners. With those pedigrees, such information has scant reliability as evidence. Nor is it likely to be in any way comprehensive. It would be natural for writers to focus on what they found novel or interesting. Technical details about navigation practice were largely ignored. As a result, an attempt has to be made to deduce some of the charts’ functions from their own content, with others inferred by analogy from documented use in later centuries.

Much of the chart’s information was offered as a supplement to experience, a jolt to memory. In some respects, the charts were information icebergs, providing triggers to various hidden layers of memorised information. This would have applied particularly to the offshore hazards and archipelagos. No memory is infallible and it must have been reassuring for a helmsman on a long course to be able to check the required changes in direction, potential obstacles, or expected landmarks lying ahead.

The chart’s main, and indeed unique, contribution was to give unprecedently precise relative locations for navigation targets (usually capes, islands or ports). Its other obvious uses were for route planning, landfall recognition, a littoral toponymic catalogue for when sailing along a coast or in an archipelago, and warnings about offshore dangers.

The portolan chart’s format was ideal for shipboard use: drawn on a durable animal skin, it could be rolled and perhaps stored carefully in a tube away from damp. Or, alternatively, it might be in the form of an atlas, whose outer boards would protect the folded sectional charts within. Sensibly, overlap was provided between the individual sections. Later, a single chart might be attached to a pair of folding hinged boards, for both conservation and ease of storage. Drawn or written on each chart was information, of different types and from different sources, clearly and consistently presented and gathered into a single place. Despite the small scale, all the salient features could be clearly seen at one view.

Many sailors would have owned their own charts but it is probably more helpful to envisage their usage as a shared experience. Once it had been unrolled or, in the case of a bound collection, opened at the relevant place, there would likely be more than one person poring over the document. In any discussion about a future route, or disagreement about the ship’s location, the chart would be Exhibit A. Such a scenario, which could also have involved a literate crewman reading off the place-names to his unlettered fellows, stresses once more the central place of oral transmission in medieval navigation practice.

Few, if any, mariners would have had the concept of a chart in their mind before they encountered a portolan chart, but after a brief oral explanation any experienced navigator would surely have understood its meaning and realised the ways it could help him. Portolan charts would never have been invented unless they had satisfied definite needs. On the earliest charts, pragmatism was king. Their compilers worked on a need-to-know basis and pared their content down to a pilot’s navigational needs, and nothing beyond that.

At first, perhaps providing little more than reassurance – for example, about the position of nearby islands – the portolan chart would quite quickly have become an indispensable navigational tool. The widespread ubiquity of chart use, which we are only slowly coming to appreciate fully, 479a is a resounding endorsement of their practical value. Medieval sailors must have fully trusted them. No criticism of them by early users has been noted, which complements the lack of significant changes after about 1330.

Finding confirmation in the depiction of areas pilots already knew would have provided confidence in what lay beyond their own experience. The accepted overall reliability of the portolan charts could provide certainties where there had previously been estimations and thus help avoid or resolve an argument. Indeed the reason we sometimes learn about their use at sea is because of a dispute over the ship’s position.

Spatial accuracy – ensuring the avoidance of significant, possibly fatal errors – was not a luxury for mariners but fundamental to the charts’ purpose. Among other promptings would undoubtedly have been the need to find a safe harbour in which to shelter from bad weather, or to identify likely landmarks after a ship had lost its bearings during a storm – as illustrated by the Louis IX incident in 1270, described by Guillaume de Nangis. 480 

The more we look into the features of the portolan charts, the clearer it becomes that they were designed for pelagic seamen, those who sailed away from land rather than along it. When those who ranged more widely saw their first portolan chart they would surely have appreciated how their own incomplete knowledge could be fitted into its overall pattern, and hence that they could additionally discern what would be involved in a course not previously sailed. While their main concern would have been with the open-sea courses, some pelagic sailors would have needed to know the sequence of capes and ports, for instance if they reached a coastline some distance from their planned landfall. Which way should they turn and how far or how long would the correction take?

A mariner, even when repeating a route, would still have needed contextual information. The chart allowed him to identify the land he was glimpsing ahead or alongside so that he could confirm or correct his course. A long passage was rarely a matter of simply holding a single bearing. Even in a galley, adjustment had to be made for the wind, currents and swellThe regular movement of rolling waves that do not break. In particular, a changeable wind might force alterations to the known course, perhaps involving passing an island on its other side. If he had been blown off course in a storm, the pilot would probably have turned to his chart to help regain his bearings.

A sailor would have clear visual memories of the ports he had left behind and those he had visited, as well as the appearance of the islands he had passed or landed at, or perhaps just glimpsed in the distance. But it is not possible to plot or memorise the open sea, which is featureless empty space. So a vital function of the chart in those circumstances was to indicate what unseen land lay ahead or alongside.

The subsequent history of the portolan charts confirms those continuing purposes. Mariners’ belief in the charts’ utility would have been matched by the chart copyists’ realisation that it was vital to preserve the positional accuracy of the network of pelagic courses (as reflected primarily in the placement of the pivotal headlands). Only in that way would the charts remain relevant for navigational use. Hence the care with which the basic geometric structure was directly copied from the workshop model. By contrast, the focus on decorative adornment in the 16th and 17th centuries appears to have been largely aimed at a non-sailing clientele, which helps explain the charts’ steady hydrographical degradation as a result of careless copying. Positional accuracy had clearly lost its primary role by that stage, at least for some chartmakers.

M.1a. Planning a voyage

When leaving port, the direction, or heading, to the destination was the single most important piece of information, whether known by direct experience or by report. From that, it follows that one of the main functions of the portolan charts must have been to aid the selection and definition of a route, while at the same time placing it into the wider context of the overall coastal and insular configuration, along with any likely hazards.

Before embarking, the sailor needed to select the nearest ‘wind’ or compass line on the chart and note by eye just how close his course should be to that. Alternatively, because the chart would not tell him about the currents or detailed configuration of the navigational dangers near to the port, he might have tapped into local knowledge. As Barry Cunliffe pointed out: ”A sensible ship’s master intending to sail in unfamiliar waters would have taken the advice of locals before venturing out of port, much as Odysseus did in seeking instructions from Calypso. In this way networks of knowledge were constructed.” 481  This potential oral source seems to have been generally overlooked by portolan-chart historians. Those who worked in a port were the most likely to know about the bearing that needed to be taken when leaving that harbour for any of the usual destinations from there. It seems probable that helpful harbour-masters, fishermen or other locals, would have routinely provided enquiring sailors with the distance and direction for the pelagic courses that fanned out from there. Such standard instructions could have been continuously refined in the light of reports from returning sailors. Pilots who were met with ashore could have served a similar function. What was learnt from colleagues could then have been memorised, alongside the details of those courses that had actually been sailed. This insight might assign a further important role to harbour-masters and other port-based individuals in the devising of the calculations that had underpinned the original chart.

When it came to distance, the navigator would need an indication of the length and duration of the entire voyage. After measuring off the course (or translating the mileage figure into days’ sailing), he would need to note the planned stopping-points that would break the stated course into separate legs, and specifically the distance to future landfalls so that he could carry sufficient supplies and water. He would also have to plan for any detours to avoid dangers, such as the long Skerki Bank. None of that information could have been obtained from the portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes.

A stated pelagic course should be seen as aspirational, an ideal route. Sailors never wanted to reach a coastline before they were ready for its challenges but they would seldom have arrived precisely at their aiming point each time. Even a minor heading error could take them many kilometers off course. That could mean losing money because of the time taken to sail that extra unintended distance. If an error of that kind happened, and they needed to identify the coast in front of them so as to know which way to turn, the chart’s toponymy would come into play by showing the pilot the sequence of intervening places and hence how much further the vessel had to travel.

M.1b. The advantages to a navigator of a chart over a portolano

The so-called pelagic statements in the written guides are very summary, mostly reduced to the essentials of distance and direction. It is now generally accepted that those statements were not real courses but initially measured, as straight lines, off a chart or a precursor diagram. 482  A helmsman would have needed to consult the portolan chart instead to see when to alter course, say on a dog-leg or around an island, or to work out what action was needed to avoid a hazard. When land was in sight in two or more directions the chart could confirm the bearing.

If somebody was using the LiberThe ’Liber de existencia riveriarum’, c.1210, written in Latin, is the oldest surviving guide to the Mediterranean, giving the distance and direction between places along the coast and across the open sea (Cotton MS Domitian A XIII, ff. 114r–129v) to find details of the direct distance and bearing involved in a specific open-sea crossing (per transfretum pelagi) they would have had to search in its text. Alexandria, for example, features twelve times in the index to the modern edition, pointing to seven different parts of the work. It is not clear, therefore, how easily the reader would have located the single theoretical route from Alexandria, to Patera in Asia Minor (lines 763-4: 650 milliara, in austro (south)), particularly as that information is given in the Patera sequence only [though it is repeated in the ‘Contents’ under Alexandria]. That, incidentally, suggests the possibility that the Patera–Alexandria route was one that the Liber’s author might have taken himself. 483 

To use a work like the Liber or Lo compasso’Lo compasso de navegare’, c.1260-96, written in Italian and apparently designed for sailors, is much more detailed than the earlier ’Liber’ (Staatsbibliothek, Berlin, MS Hamilton 396) while on a coasting voyage, you would have had to be literate in the language involved (Latin or Italian). If you wished to find a place or feature, you would first have to locate the relevant stretch of coast, and then find that section in the unindexed text. You would then search out the toponym you required, which, if you were proceeding along the coast in the opposite direction to that of the text, would mean reading backwards and reversing the stated wind directions to the next place.

It may not be so surprising, therefore, that there is little evidence that portolani (Singular portolano and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes (or the ancient periploi that preceded them) 484 were actually used for navigation. Later, at least, it appears that they were written not on vellum but on paper (which would not have coped well with the damp at sea), and they do not seem to feature frequently in sailors’ inventories. 485  In whatever way the chart and early pilot book might have been related to one another – tenuously it seems – their functions were very different.

However, the situation is not entirely black and white. Alessandra Debanne supplies a valuable glossary of the technical terminology of the medieval sailor as preserved for us by the creator of Lo compasso. This comprises words referring, inter alia, to offshore dangers; the measurement of water depth with the sounding lead; the nature of the sea bottom, currents and prevailing winds; the colours and shapes of headlands (to aid recognition); landmarks of whatever kind which could be used to fix the vessel’s position; places where ships could find a mooring or safe anchorage; and landing arrangements at ports. Details such as those could only have been directed at sailors. But it is unclear just how practical a volume of that kind could have been at sea and how much they were actually utilized on a voyage. Indeed, even though they were relentlessly copied and reissued over many centuries, the purpose of works like Lo compasso remains obscure. Its disparate content is likely to have appealed to different readers, whether mariners, merchants or travellers. Perhaps, as with any guide book, its users would have found it at times, essential, interesting and irrelevant. Indeed, it may have been that mixture that kept the portolani in circulation into the 18th century.

As already described, the symbols used to depict rocks and shoals were one of the portolan charts’ most important innovations. 486  Nevertheless, whereas the Liber makes few references to those hazards, Lo compasso locates and provides descriptive details of far more of those features than does the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . Where Lo compasso’s author obtained that information, and at a time perhaps one or two decades before the Carte Pisane, remains a mystery. 487 

In addition, the portolan texts were inevitably subject to corruption, whether by introduced errors or omissions. Patrick Gautier Dalché picks out various mistakes, caused by faulty copying or other reasons. 488  Sometimes that involved vital information such as distance measurements or directions. In the case of Lo compasso there is also a noticeable gap in the toponymy along the Libyan coastline between monte de barca (Djebel al Akhdar) and c. de lasueca (Ra’s Maeri). This roughly coincides with the stretch between rasuthen (Ra’s Amir) and rasautino (Ra’s Attin). Might those similar contemporary versions of the Arabic names have caused confusion, leading to the intervening names being skipped? 489 

In contrast to a written portolano (Plural portolani and more usually called ‘portolans’ – which can be confused with the charts) these were medieval guides to the coastal places around the Mediterranean, listing the distances between them. They also include open-sea (pelagic) routes, once a way had been found to replicate a portolan chart directly from a master copy, and assuming that sufficient care was taken in the copying process (which is not the case with all the post-1550 charts), it is impossible to omit a section of the coastline, nor could the sea's shape have been distorted or the relative positions of features changed.

Nevertheless, besides the navigational details mentioned above, a mariner engaged in the cabotage trade might have found useful the more precise measurement of the distances between neighbouring places in a portolano, since those were only located approximately on the portolan charts. Though how that was calculated – as the crow flies or the actual distance involved – is not clear. 490  However, overall, it is hard to see what of the information provided in the portolani would have usefully supplemented the pelagic pilot’s portolan chart.

The clearest case for the charts’ greater utility may be seen in their ubiquity and longevity. It seems clear that the unknown creator(s) had hit on the right formula, which would therefore be continued (broadly unchanged) by those who stepped into their shoes to take the nascent charts through their inevitable teething difficulties in the period up to the Carte Pisane (c.1270). The tentative elements of that earliest survivor betray a ‘work in progress’, yet the conventions and cartographic language used there remained recognisably the same for centuries. It can reasonably be assumed that what a sailor purchased, in a competitive market, contained what he wanted. Devised, constructed and used by the same people, there would have been no need to second-guess the precise practical requirements involved. This may explain why later chartmakers, who could be innovative in relation to the inclusion of place-names, otherwise added little of note.

M.1c. The portolan charts’ limitations

Part of the charts’ shipboard role was to provide a reliable spatial framework against which the individual sailor could deploy his memorised observations. Hence a mariner could never be entirely reliant on his chart alone. 491  They were a necessary part of a navigator’s equipment, vital even, but of limited use without the backup of training and experience. If the main purpose of navigation was to know your position when no land was visible, then the portolan chart was of limited value – just like any other marine chart when used without external navigation aids.

Furthermore, a portolan chart was not suitable for all situations. It would have been of less value to in-shore sailors, who would surely have known the details of the coastline and its toponymy beforehand. Galleys, for instance, rarely ventured out of sight of land, and when they did so, this was a matter to be noted. 492  In addition, some mariners managed without a chart at all: for example those could have been of little assistance when dealing with the widespread shoals in the Black Sea. There, as Fra Mauro explained, the sea “is not navigated with a map and compass but with a sounding-lead”. 493  Likewise, those sailing in the North Sea saw no use for a marine chart, relying on memory instead, as illustrated by Chaucer’s late 14th-century ‘shipman’:

His stremes [currents], and his daungers hym bisides,
His herberwe [harbours] and his moone, his lodemenage, [pilotage]
He knew alle the havenes [harbours], as they were,
Fro Gootlond to the cape of Fynystere,
And every cryke [inlet] in Britaigne and in Spayne …' 494 

M.1d. Usage by non-mariners

It was not only pelagic mariners, of course, who used portolan charts. Anybody who coasted along an unknown shoreline or sailed out to sea as a passenger would have been able to gain useful information from a chart. Others could have turned to it because it was the only realistic picture of what was known of the world at the time. They would have used it for its geography, not the hydrography. Non-mariners, such as travellers and pilgrims, must sometimes have asked a sailor to show them the ship’s current position and the planned route on his chart. However, if they looked further they would have failed to find the information they might want about antiquities and the holy sites. 495 

The portolan charts might have been responsible for another possible effect. By providing the full Mediterranean context, this must have increased confidence when setting a course. Many sailors would have been repeatedly following the same routes; could the portolan charts have given them, and their merchant paymasters, the impetus to use new routes?


Table of Contents


For brief summaries see the Conclusions


 

N. COMMERCIAL ASPECTS

 


 

N.1.  THE PORTOLAN CHART AS AN OBJECT OF COMMERCE

Assertion: There can be no discussion of the portolan charts’ origin without considering their purpose(s); or their purpose without looking at usage; or their usage without considering them as objects of commerce.

The only available information about the financial aspects of portolan-chartmaking dates from later centuries so we are left to conjecture how the commercial transactions operated in the earliest periods.

Nevertheless, a number of assertions can be made without much danger of contradiction:

Ramon Pujades has estimated that a basic, functional portolan chart was sold at “approximately two Majorcan or Genoese pounds per chart, which amounted to less than two weeks of a naval officer's average salary”. 496  Coincidentally, it might well have taken the practitioner a broadly comparable time to produce a single, purely functional chart. 497  But viewed in another way, and considering today’s values, that price could have amounted to what would have been a significant outlay of around 1,000 euros, for a single chart that would need to be replaced once it was too worn or damaged. So, besides being clearly necessary, the chart also had to be looked after carefully.

N.1a. How might the market have been established?

It is fair to assume that those involved in the charts’ creation would have been among the first to request (or draw) a copy for themselves, as well as acting as evangelists among the other mariners they encountered. How would anyone have accepted the portolan charts' outlines and copied them faithfully unless they understood that the charts’ revolutionary geometric framework did indeed mimic reality. That can also explain why the hydrography was treated as sacrosanct by the chart copyists (apart from a few early improvements), while some of the other elements were left to personal choice.

Furthermore, the charts’ evident utility might help answer the crucial question as to how a replication business could have been established in the first place, and then have survived through the decades up to the time of the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . For the central point here is that, from very early on, once the charts had become useful for actual navigation, sufficient copies would need to have been produced not only to create but also to maintain a market. In other words, the portolan chart would have had to pay its own way.

Almost continuous production, even if only part-time, or involving no more than a single dynastic family, can be assumed as well. Like any novel device brought to market, the chart draftsmen would have needed repeated orders to give them sufficient motivation to persevere. A critical mass, based on a habit of use, would have been essential for both parties. If those assumptions are accepted as probable, that would provide historians with indirect evidence of the charts’ usefulness – even if that might be considered a circular argument.

Long-distance sailors formed part of an unparalleled information network. Those who embarked regularly on trading voyages must have visited more foreign places and encountered a wider range of people than the members of any other profession. In the Middle Ages, most news from foreign parts travelled by sea, which was fast and convenient. It was those knowledge routes and connections that must have helped both to familiarise sailors with the portolan chart and distribute it, thus accelerating its adoption during the early years. Not only did they become ubiquitous, they must also have been their own ‘pollinators’, spreading fresh information that could be used to update the work of other practitioners. The unforeseen consequences of that same interconnectedness can be seen when the Black Death was carried speedily from Crimea to Europe, and then throughout it (which presumably explains the gap in dated charts between 1339 and 1367).

Suggestions that the creators of the portolan chart must have needed financial and organisational help – reflections of an outlook that perhaps unintentionally denigrates artisanal achievements – can be readily countered. There is no evidence that any individual or institution was sponsoring charts, apart from Pietro Vesconte’s provision of portolan charts to illustrate Marino Sanudo’s Liber Secretorum Fidelium Crucis in the 1320s. Had such support been involved it could presumably have applied only to the single Italian port where the first charts had originated. The evident dispersal to other coastal cities after the Carte Pisane, if not before, weakens further any argument for focused external support at the outset. Since that development belongs to the first chapter in the charts’ recorded history, it cannot directly inform the ‘Origins’ debate. However, as has been said before, information from the first documented period may have analogous relevance when conjecturing about what might have preceded it. That apparent fanning out from the unkown birthplace is discussed in the following sections.

N.1b. Not a single lineage

Whatever superficial similarities there might be between the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) and the charts that followed, now preserved in CortonaBased on its archaic appearance, this is considered to be the second oldest surviving portolan chart after the Carte Pisane, dating from the beginning of the 14th century or even earlier. It was first described in 1957 (Biblioteca dell'Accademia Etrusca di Cortona, Port. 105), AvignonA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html and LuccaDiscovered in 2000 in the city archives, this is visually very different from other charts from the 1st quarter of the 14th century (Archivio di Stato, Lucca, Fragmenta Codicum, Sala 40, Cornice 194/1) , as well as the Riccardiana chart The oldest Genoese chart, probably dating from the second decade of the 14th century (Biblioteca Riccardiana, Florence, 3827), Carignano map/chartDrawn by the Genoese priest Giovanni da Carignano c.1325-30, this is a hybrid of a map and marine chart. Florence, Archivio di Stato, C.N. 2 [destroyed in World War II] and Library of Congress chartThe oldest portolan chart preserved in the USA, probably dating from the second quarter of the 14th century, it was acquired by the Library of Congress in 1914 – which should presumably be arranged (in what order?) in the period between the Carte Pisane and the end of the Vescontian output (c.1270-c.1330) – there are no pointers to a single centre for portolan-chart production over that period. While the last three of those charts are evidently of Genoese origin, there seems to be no good reason why the others could not have been made in four different Italian ports.

It is also worth pointing out that three out of that group of seven have unique elements, which suggests they might have been created for other purposes than navigation (not being used at sea may also explain their survival). As described by Jacques Mille, who has studied it very carefully, the Avignon chart is the earliest survivor to treat the North Sea coasts, and, uniquely, includes profiles of ecclesiastical buildings; 498 the Lucca chart has elaborate city signs; 499 and the Carignano map mixes the characteristics of both a marine chart and a topographical map. 500  Nevertheless, among that list of early unsigned charts there are some shared features. We are left to speculate about the possible significance of the supplementary squared-off compass-line grid on the Carte Pisane and the Avignon chart (and the equally incomplete system on the Cortona chart), the repeated guardate, guardate (indicating a non-existent rock) on the Carte Pisane and Lucca charts, or the partially overlapping toponymy of the Carte Pisane and Cortona chart. Those occasional shared features are outweighed, though, by the disparities within those pairings. The overall impression is one of stylistic heterogeneity; nor is there any justification for assuming that those early survivors are in any way representative of what was being produced during that period.

Each chartmaker would have copied the coastlines and offshore danger markings from an earlier exemplar, while simultaneously reproducing most of the same toponyms. In other words, they shared a common cartographic ‘language’, which indeed is what provides the best (if unscientific) definition we have for a portolan chart. Given that the chartmakers were mostly port-bound, how could any consistency in the charts’ content have been maintained? The likely answer is that each was kept informed of developments elsewhere through being shown the charts of other makers.

Yet there was little borrowing of the more obvious visual features. Chartmakers, it seems, wanted their work to be recognisably distinct from their forebears and competitors, a tendency that can be seen continuing into the later centuries.

Had any two of those seven very early charts been in the same hand, we could probably have determined which was the earlier of the two, thus helping to identify at least one practitioner’s development, but that is not the case. From another direction, when trying to order the seven chronologically, there is a valuable tool in the largely reliable yardstick of the expanding toponymy and the emerging outlines of the British Isles introduced into Pietro and Perrino Vesconte’s Pietro Vesconte (fl.1311-c.30) is the first chartmaker known to us by name, and the first professional. A Genoese, he worked in Venice, along with his presumed relative Perrino. Several of his works survive, documenting in particular the growing shape and toponymy of the British Isles. His chart of 1311 and atlas of 1313 are the oldest to be signed and dated charts in the 1310s and 20s – on the assumption that those additions were indeed introduced by the Vescontes and not somebody else from whom he had, in turn, borrowed. However, that does not allow us to say confidently that a particular chart was drawn before or after Vesconte’s productions of, say, 1318 because there is rarely a precise match. The Riccardiana chart, for example, can be placed earlier or later than Vesconte’s atlas of 1313 depending whether the focus is on its toponymy or the Atlantic outlines. 501 

This lack of clear developmental patterns means that it is almost impossible to place these early survivors into any reliable chronological sequence. Had two or more of those early charts been produced in the same port we would expect to have seen close overall similarity. But there are no signs of that, thus firmly contradicting any notion of a single ‘school’. All that can be said with some confidence is that the post-Carte Pisane charts that have been singled out here are possibly spread over a 25-year period (c.1300–25). A few lean more obviously towards the beginning of that span but unless new diagnostic methods are devised it is unlikely that any of them will be dated with anything approaching certainty.

We might have expected, since precise repetition seems to have been hardwired into the portolan charts’ DNA, that the earliest examples would reveal, through their consistency, close copying from one another. That this is not the case implies that the chartmakers, and perhaps the places of production, must have already branched off at a fairly early stage. With the portolan chart’s emergence now provisionally placed before the year 1200 and the Carte Pisane at around 1270, there would have been plenty of time for that process to have occurred.

Indeed, that would have made sense. Once a demand for charts had been established, it would have been logical to have had off-the-shelf, working charts available wherever sufficient numbers of pilots gathered. They would not have wanted to make a special journey to the chartmaker’s port and they might well need a replacement when far away from there. In a similar way, there must have been ships’ chandlers in the major trading ports; after most long voyages there would usually be pieces of equipment that needed to be replaced. A chart might well have been one of those.

Counter-intuitively, therefore, it seems that the concentration of portolan-chart production in organised workshops in (mostly) three cities, Genoa, Palma (Majorca) and Venice, from perhaps 1320 until well into the 15th century, had been preceded by a period of distributed, informal local production in family ateliers, 502 and would later be followed by a dispersal among a growing number of major Mediterranean ports.

N.1c. Dissemination

Prior to the circulation of printed texts in the later 15th century, the portolan chart must have been reproduced (sometimes with intentional modifications) in greater numbers, not just than any other map but probably any other coeval document besides religious texts. 503 

The oldest direct reference to what must have been a marine chart is 1270; 504  they are mentioned a number of times in the 14th century and, by the 15th (if not earlier) they were being talked about as essential aids. 505  Hence, if a Mediterranean mariner had encountered one, say in 1220, it would probably have been the first map he had seen. By 1320 they must have been circulating generally and, well before 1420, they would have become commonplace.

The 180 or so charts and atlases that survive from before 1500 were joined by many hundreds in the 16th and 17th centuries. 506  It also seem likely that a wholesale trade would have grown up, perhaps before it was first documented in the 15th century. 507  The 24 charts that Gabriel de Vallseca was required to provide for a merchant to sell on, gives us a glimpse of that process. 508 

Because of the exigencies of use at sea, each surviving functional chart might represent hundreds, or more likely thousands, of those actually produced. 509  Essential, and also ubiquitous, the portolan chart would have been found on nearly all long-distance trading vessels and could probably have been purchased in most Mediterranean ports. No Christian mariner could have been unaware of them, while Islamic sailors clearly used them and made copies in their own script.

Charts with the traditional coverage also enjoyed an unprecedented longevity, being made, sold and used for about four centuries, from no later than 1270 up to around 1700 [Powerpoint, Slide 26]. The introduction of printed alternatives in the 16th century (such as Nicolas de Nicolay’s of 1544) does not seem to have done much to dent their popularity. The two most likely reasons for that are, first, their convenience and robustness in the context of seaboard use and, second, the fact that most of the printed versions imitated the portolan charts (in a much reduced format and with fewer names) rather than superseding them.

N.1d. Apprenticeship

The question of apprenticeship – how it might have operated and when it was perhaps introduced – follows naturally from the preceding section. Perrino Vesconte (fl. 1321), presumably the son or nephew of Pietro (fl. 1311), the first chartmaker to leave us a signature, seems to have been trained to produce work that was indistinguishable from Pietro’s. That is what we would expect from an apprentice, who would usually have started out when very young. The training process would probably have included being taught to read. The apprentice would also have been required to insert the toponyms in imitation of the master’s hand, and reproduce very precisely the house-style for each of the chart’s elements. Nevertheless, if that Vesconte instance indicates some kind of apprenticeship, it is exceptional.

Despite assiduous searching, Ramon Pujades found no apprenticeship records for Catalan workshops in Palma, Majorca, before 1368 and, for Italy, before 1427. 510  There may well have been other instances of which we are not aware but no signs of apprenticeship have been identified among the early surviving charts. Instead, what is immediately evident are the obvious differences, as was found when comparing, for example, those six early unsigned charts: Carte Pisane, Cortona, Avignon, Riccardiana (Florence), Lucca and Library of Congress. 511  Had there been apprenticeship – in other words if those who drafted the charts had learnt their craft during their formative years – we would expect to see close imitation in both the charts’ fundamental structures and their overall style.

One specific feature that is worth a full study is the handling of the twin-circle compass network, which was prevalent up to the end of the 14th century. Where the circles meet (at the point of tangency) the area above and below falls outside the network of compass lines, so that anyone sailing in those areas would have had to mentally supply the missing directions. The various methods devised to deal with that omission, which affected what was the most routine of the chart’s elements and the one that was probably inked in first of all, are likely indicators of a chartmaker’s stylistic signature. For example, the Carte Pisane and the Avignon chart bridge those gaps, rather clumsily, with sections of squared grids. Unfortunately for this diagnostic purpose, the limited coverage of two of the other four charts mentioned above ruled out the need for twin circles. Hence, only those in Florence and Lucca had to deal with that problem, which they manage more confidently with additional, but different, geometry.

What conclusions about apprenticeship might we draw from this? There are two likely ways a copyist could have obtained the complete chart he needed for his model: (a) from copying the pattern used in the atelier where he was working, and then setting up on his own, or (b) simply transferring the details from an existing chart. The first method is likely to have reproduced both the constructional method used for the model and its detailed content; but in the second instance – where the copyist had not been trained in that particular style – new procedures would have had to be devised. The tight discipline enforced on a trainee copyist is likely to reveal itself through the repetitions of distinctive features in his own later productions, which can serve to identify the master-apprentice link 512 [Powerpoint, Slide 28].

Had the nascent chartmaking production been concentrated in a single port – and Genoa is sometimes mentioned in that context without, in my view, convincing evidence 513 – we would expect any expanding ‘school’ to have developed its own shared characteristics, as would later be the case in Majorca. But there is no sign of that in the early decades.

N.1e. Customisation

Each chart was of course hand-copied, but that does not mean they had to be identical. Although this might only apply once a market had been fully established, the purely functional examples could well have been pre-prepared so as to be available for immediate sale. The date and signature (if that was thought necessary on such a mundane object) might have been added at the time of purchase. 514  One or two of the examples that included a limited amount of illustration might also have been drawn beforehand for off-the-shelf sale. But it seems likely that those charts with a considerable amount of adornment would have been made, over a period of weeks or even months, to a customer’s specific requirements. 515 


Table of Contents


For brief summaries see the Conclusions


 

N.2.   THE PORTOLAN CHARTS AND THE WORLD OF TRADE


N.2a. The possible contribution of merchants to the charts’ origin and development

That the portolan charts might have been invented by merchants, made for them, or financed by them, have all been suggested. 516  One way to test that is to consider what a chart designed by those who bankrolled the trading voyages might realistically have contained.

There is no reason to suppose that the merchant class would have been interested in the location of headlands by which the sailors steered and on which the charts’ geometry is based. Nor are they likely to have asked for the inclusion of the intricate details of the offshore hazards. They might have valued the city pennants proclaiming the ports’ political allegiance, but those were not added until about 50 years after the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . 517 

Moreover, if the merchants were the controlling force behind portolan-chart production, we would have expected them to insist that the heraldic designs were kept up to date, which in practice happened only irregularly. Likewise, if those who valued the charts for their ornamental qualities – perhaps for display on the office wall – had been involved in their creation, there would not have been such a long wait until those ‘augmented’ versions started to appear around 1330.

Furthermore, some absent features can be mentioned, which the trading community might have welcomed if the charts’ central concern had been with mercantile matters, rather than navigation. Had the charts been sponsored by merchants, they might well have asked for some of the major routes to be indicated. Those through the Aegean Sea would have been an obvious instance (preferably paired for the outgoing and returning directions) with a figure alongside stating the average duration in hours or days. If the sailors were able to devise a code for different types of navigational hazard, merchants could have demanded classified information elsewhere, say by using symbols or numbers to distinguish the different types of customs dues. The depiction of rivers on the charts falls loosely into three broad size categories, with the majority undifferentiated. It is reasonable to suggest that shipowners might have appreciated colour being used to distinguish the nature and extent of any upstream navigability. 518  Obviously none of that was done, which surely gives the lie to any suggestion that the primary motivation behind the wholly original portolan chart was a response to the needs of the mercantile class rather than mariners.

As to the financing of the original charts themselves, it would have been perfectly possible for a state, an institution, or a group of merchants to have put forward the necessary funds, but there are no signs of that. All the available evidence points instead to artisanal arrangements, demonstrated later by the signed works bearing the names of the separate families involved. Even when the Majorcan Gabriel de Vallseca signed the contract (already mentioned) to produce 24 charts at the rate of one a week, the debt involved remained within his family. 519  Likewise in 15th-century Venice, from which a sizeable percentage of the surviving charts emerged, often without signature, and where one might have expected state involvement, there is none of the uniformity in the charts’ appearance that would back up the suggestion of centralised control and production.

None of the above denies the benefits offered by the charts to the mercantile class. Any 13th-century merchant or financier, who was involved in foreign trade without necessarily going to sea himself, 520 would doubtless have known something about trade routes and journey times. But is it likely that he would have previously encountered a map of any sort? Now, for the first time, he could ‘see’ for himself the entire Mediterranean, including the relative positions of the ports and islands, without having to rely on his ships’ crew for that knowledge. No doubt they would have reassured him about the charts’ overall accuracy.

It is easy to imagine the merchant discussing routes in front of the spread-out chart before his captain left the home port, learning the distance (or more likely the time) involved in the various planned phases of the voyage: first reaching the initial destination and then perhaps any cabotage hops that might follow. The captain could also have explained why some apparent routes involved adverse winds, or were too dangerous (whether because of hostile powers, pirates or navigational dangers), or where deviations would have to be made. The owner might not have already known the sequence of coastal toponyms, and would be glad of the way that they were so conveniently set out on the chart. Perhaps studying a portolan chart might even have drawn his attention to other trading possibilities. As the 14th century progressed, it is hard to imagine a sizeable merchant house that did not own at least one chart. 521 

All of which demonstrates the usefulness of a portolan chart to the merchant houses, while providing no support for any direct involvement from the trading community in the charts’ creation or subsequent development.

N.2b. How important was trade in the charts’ origin?

It is natural to consider that the time and place of the charts’ creation might reflect a particular conjunction of trading patterns and opportunities that resulted from the growing prominence of one or other of the Italian city states or Catalonia. 522  One suggested trigger was the opening up of the route through the Straits of Gibraltar and out of the Mediterranean, which had been closed by the Almoravids in 1107. But that restriction did not end until Alphonse X captured Cadiz in 1262, which is too late to have relevance for portolan chart origins. No other event, falling within the likely window for the charts’ appearance (1154-1200), looks a plausible candidate for a trade-stimulated origin. 523 

The timing for the portolan charts’ appearance, its immediate prompting, is unknown. But why does there need to be a specific trigger for that event? It could surely have happened at any time, if the magnetic compass is ruled out as a necessary pre-condition. 524  Trade continues ceaselessly, unless effectively impeded, and a general chart of the Mediterranean would have had the same relevance in different periods, regardless of changing cargoes and destinations. If the pelagic information was held in the memories of numerous sailors, all that was needed was the spark of recognition that their shared knowledge could be given graphical form in a marine chart. Once a prototype chart was seen, its usefulness, even necessity, would have been evident.


Table of Contents


For brief summaries see the Conclusions


 

N.3.   SHOULD WE DIVIDE THE PORTOLAN CHARTS INTO TWO TYPES?

The portolan chart was, first and foremost – and exclusively so in the early period – a tool for navigators. Only later are aesthetic considerations noticeable and only around 1330 (perhaps over half a century after the oldest survivor, the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) ) can we start considering them as works of art. Might there be a valid argument for dividing the history of portolan charts into two types? First, those clearly designed for use at sea and assumed to have been sold to sailors, which are termed here ‘Functional’; and, second, those displaying varying amounts of information and adornment that had little or no relevance for practical navigation, and were intended instead for other types of use, designated as ‘Augmented’. Although the visual difference between the ascetic and aesthetic approach is very evident at the extremes, the surviving charts represent a continuum, dependent on the level of elaboration [Powerpoint, Slide 29]. It is not clear whether or not the hybrids, exhibiting some non-functional elements, might have been taken to sea, but, for practical reasons, this seems unlikely.

Although it is conceivable that a very early augmented-type chart might be discovered, the chance is small. The ‘origin’ which this essay is examining concerns a navigators’ chart; the elaborated versions, on the other hand, illustrate how the basic template could be adapted and extended, often for non-maritime purposes. Nevertheless, all those that display the common underlying features are, for convenience, deemed by historians to be ‘portolan charts’.

To repeat a point made earlier, there was no difference, in their hydrography and toponymy, between a functional and an augmented chart, probably because each started out in the identical way, with an artist only being called in at the end to work on the second type. 525  Had the portolan charts not continued to share the same faithfully copied outlines throughout their long existence, and had those who produced the ornamented charts broken away completely instead, the cartographic elements (hydrography and toponymy) would have become thoroughly debased, and ultimately unrecognisable. Because that never happened, it may mean that most of those who created the augmented charts also semi-mass-produced the basic versions, which are now either lost or unrecognised because of the absence of a signature.

The same visual qualities of the augmented charts that appeal to us today must have been part of what attracted them to their first owners: the nobility, wealthy merchants, or others in the higher levels of society. They would have valued them as objects to be proudly displayed. But surely some would also have appreciated that they were far and away the best outline map of the time, covering most of the then-known world. Owning one could have also provided evidence of geographical erudition.

This is not to decry the relevance of the augmented charts for historians. The so-called ‘decoration’ and discursive legends, found on the empty inland spaces of Catalan charts from around 1330, provide factual, mythical, historical, geopolitical, artistic, and social information of considerable, and sometimes unique, value for researchers in many historical fields. It is also a testament to the chart’s versality that it could manifest itself in different guises, offering instruction of various kinds to a wide range of users – and all with a single underlying template. But, if the portolan charts are considered to belong primarily to the history of navigation, it is the functional type that carry the authentic messages, which were to guide sailors for centuries, and helped to keep them safe. On the other hand it is possible that it was the more profitable ornamented examples that kept the chartmakers in business, as the demand from sailors declined. 526 

That the charts were created with a purely practical role in mind does not exclude the possibility that modifications could have been made later in response to demands from non-navigators. 527  The flags and other illustrations are obvious examples of that. But the way that such features become increasingly prevalent after, say, the mid-16th century, sometimes obscuring cartographic detail in the process, testifies to a lessening of the link with active navigation.

Charts of the two types may now sit alongside one another on a library shelf, or be displayed next to one another in an exhibition, but they must have belonged to different worlds: the ship’s locker contrasted with the merchant’s office or the residence of an affluent non-mariner. It is their different purposes and the separate development of the features added to the ‘augmented’ examples, which prompts this possible conceptual division into two formal categories.

N.3a. Survival

When considering those different types of portolan charts (the ’Functional’ and ’Augmented’, described in the previous section) it is essential to take into account the circumstances that led to their very different rates of survival. Lacking any legacy value, the functional charts had a vanishingly small chance of being preserved. By contrast, examples of the augmented group benefitted from their visual attractiveness to win a more prominent place in institutional and private collections, and hence, because of their higher visibility, in current literature as well. Likewise, whether a chart – from either category – was drawn on a single skin or sectioned up to be bound into the protective covers of an atlas, made a major difference to its ultimate fate. It is highly unlikely, for example, that the surviving productions of Grazioso Benincasa An ex-ship captain, he left us a range of clearly-drawn charts and atlases (1461-82) and a written portolano (1435-45), namely eight charts [plus copies of two others in the Cornaro Atlas] 528 alongside 17 atlases, give a remotely true indication of the balance in his overall output. 529 

That some of the charts emanating from Palma, Majorca after 1330 contained visual elements which could have had no significance for a navigator shows they were designed for non-sailors. By contrast, the functional Catalan charts (which are now exceedingly rare) have none of the long text legends; perhaps the illiterate sailor did not want to pay for what he thought was unnecessary. The perception that Catalan charts routinely contained decorative elements, in contrast to those emerging from Italian workshops, needs to be firmly dismissed.

We can do no more than hazard a guess, but it would be surprising if more than one in probably several thousand of an atelier’s output were atlases or charts of the illustrated, let alone de luxe, type. A reverse imbalance applies to the survival rate, with far more examples of that ‘Augmented’ category surviving, whereas almost all the workaday charts have perished, probably discarded after long use at sea, despite being semi mass-produced. 530 

Archaeology supplies a useful parallel. A gold object is, per se, of little informational value – since it could have been dropped anywhere – whereas the smallest coin would likely point to an actual settlement. As an example, of the millions of debased coins that the Roman Emperor Tetricus I was issuing daily, only four have yet been found. 531  Likewise, portolan-chart history needs to focus more of its attention on what has disappeared: the many thousands of functional charts that were bought and used by ordinary sailors, and finally discarded when worn out in service. It is ironic that examples of purely functional charts, both Catalan and Italian, are now re-emerging as fragments hidden in collapsing bindings that European archives have had to repair. It was only the recycling value of their vellum that had saved them (if only partially).


Table of Contents


For brief summaries see the Conclusions


 

O. EPILOGUE

 


 

O.1.  THE PORTOLAN CHARTS CONTRASTED WITH THE POST-1500 SURVEYS
OUTSIDE THE MEDITERRANEAN

It was not until the ships of Atlantic Europeans ventured beyond the world they knew, and encountered and charted new coastlines, that they were faced with a challenge comparable to that experienced by the portolan chart’s creators around the year 1200. Might the hydrographic difficulties, and the ways that the two eras dealt with those, provide any useful parallels? It turns out that there are both common and distinguishing factors between the charting of the coasts within the Straits of Gibraltar on the medieval charts and the Renaissance explorations beyond that in the 16th century.

With the exception of the astronomically-controlled Portuguese surveys down the west coast of Africa during the 15th century, the crude and stumbling efforts of those who first encountered America and the East, and tried to document their outlines cartographically, provide a striking contrast with the level of realism already apparent in the 13th-century Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) . This is despite the fact that those who charted the later discoveries were aided by the magnetic compass, along with a general understanding of magnetic deviation – the latter, at least, certainly not available to the portolan charts’ creators.

Part of the likely explanation for this paradox points to the fact that the original portolan chart, covering just the Mediterranean, embodied the orally-transmitted experience built up over centuries of sailing in a well-understood, enclosed sea, rich in islands. This provided ample opportunity for the creation of a composite network built around the termini of pelagic courses, a process which has here been termed ’inadvertent triangulation’An invented term for the hypothetical process by which pilots, before there was a marine chart, could have built up a mental network of the interrelationships between Mediterranean headlands, by means of observed directions and estimated distances. No mathematical calculations would have been involved. By contrast, albeit with some exceptions, the lands newly encountered after 1492 were bounded by open oceans, which did not offer helpful points of reference to assist a marine surveyor faced with an unknown coast. Nevertheless, even in archipelagos where multiple observations could have tightened up the geometry, it took a long time for the coastlines of America, the Indian Ocean and beyond to become more than partially recognisable to our eyes.

Compare, for example, the remarkably realistic Cyprus and Crete on the Carte Pisane [Powerpoint, Slide 30] with the rigidly hexagonal Ceylon of the Portuguese three centuries’ later [Powerpoint, Slide 31]. Contrast further the printed 1606 Sanchez map with the much more realistic outline found in a c.1400 version of Ptolemy’s Geographia. 532  Progress can go in two directions.

Those were the largest of the Mediterranean islands but in the respective treatments of the archipelagos there is one instance of clear, if unexpected, continuity. The portolan chartmakers of the first half of the 14th century had devised artificial, often formulaic shapes for individual islands. This had been developed as a convenient mnemonic device to help sailors distinguish neighbouring islands, and simultaneously speed up the drafting process for the chartmaker. 533  Since the cartography of the later oceanic discoveries was often in the hands of the same people who were continuing to produce traditional Mediterranean charts, it is not so surprising that a similar approach was applied after 1500. Examples from Africa, America and Asia can be seen in the Powerpoint presentation, sometimes using artistic generalisations for the large and complicated archipelagos, most notably the Maldives [Powerpoint, Slides 32-34].

It seems that in both periods, the island depictions were approached in a similarly pragmatic way. For the medieval pilot the individual shapes of smaller islands had no navigational relevance. Likewise, for the later oceanic explorers, expending surveying energy over such details would have been a distraction. They needed to know, broadly, what island groupings were where, but they had little interest in their individual outlines. Thus one of the portolan charts’ most unusual features was redeployed to present those new worlds to a Renaissance audience, in the form of imaginary markers for distant islands and archipelagos, until those could be replaced by the scientific precision of the 18th century. In that way the portolan charts provided the blueprint for the coastal outlines created by oceanic exploration. The casual approach to hydrographical accuracy in both cases demonstrates how much closer the Renaissance chartmakers were to their medieval antecedents than to the world of today. They collected and disseminated only the information they found useful. It was not a question of ability; it was one of choice.

For the origins debate, this comparison – in some respects favouring the 13th century over the 16th – makes it much harder to pursue the argument that the Mediterranean navigators of the high Middle Ages would have been unable to create such ‘sophisticated cartographic products’, when they clearly showed themselves capable of improving them. 534  Rather, they deserve our considerable admiration for, inter alia, introducing hydrographic conventions that were still considered relevant by those charting the Age of Discoveries.


Table of Contents


For brief summaries see the Conclusions


 

P. CONCLUDING REMARKS


P.1.  A mental map origin

In discussing the source material for the portolan charts, previous researchers have highlighted the traditional knowledge held by Mediterranean pelagic seamen. But this is the first time that aspect has been elevated to a primary position in the argument, even though one book came close by saying, without elaboration, that the portolan charts were “drawn by navigators from their own experience and for their own guidance”. 535 

Two paired assumptions are central to this essay. The first states that nobody would ever have routinely left port without knowing the direction to take and any islands or dangers likely to be met with on the way. The second adds the corollary that the navigator must have been confident of his ability to discern his bearings when away from land. In the pre-magnetic compass era, unless those requirements had been met the medieval sailor would have been sailing blind.

What was first proposed at a conference in Lisbon in 2016 is that it was the timeless resource of the pelagic memories alone that provided the material for the geometric precision of the lost urchart. The argument was thinly expounded and, not unexpectedly, the initial reaction was unfavourable. A dedicated paper at the second workshop in June 2018 was received less sceptically.

However, the mental-map hypothesis does little more than build on the surely incontrovertible fact that experienced sailors must have had a reasonably adequate map in their head already and a well-practised technique of spatial memory recall. Hence the source proposed for the portolan chart, and its evidently medieval origin, was less a gigantic leap and more the transference of a network of spatial relationships from one medium to another.

Documented proof that mental maps were used for medieval navigation may conceivably be found but until then we can state with some confidence that there is no valid argument against the possibility, even likelihood, of their existence. Absence of evidence is not evidence of absence. It is not just the mental-map thesis that lacks documentary corroboration; no alternative argument has such endorsement either. It can, however, be pointed out that the missing textual evidence for theories based on supposed written sources raises more plausibility issues than the similar lack when related to mental and oral knowledge, where there could not have been visible antecedents anyway. Indeed, it is contended that the charts’ origin may have been overlooked precisely because it did not have textual sources but depended instead on memorised information and oral transmission, neither of which would have left any trace. Or, it might be added, was likely to catch the attention of textual scholars.

Modern research is beginning to reveal more about the outlines of the brain and its salient pathways. What they cannot tell us yet are the limits of the brain’s capacity; much more is needed to unlock the potentiality of those vast unexplored tracts. The remarkable way-finding ability of indigenous navigators, whether on sea or land, provides relevant analogies for what must surely have been achieved by medieval pilots as well, using acute sensual awareness (now lost to almost all of us) and an encyclopedic understanding of sea signs.

P.2.  The charts’ creation

We expect maps, however innovative, to evolve out of earlier ones; there are few examples in the history of cartography where they have emerged seemingly parentless. The London Underground map/diagram is a rare example, but so also, it seems, are the portolan charts. They are both sui generis and we should therefore not be surprised that the charts' content was expressed in novel ways. Indeed, it is clear that their creators did not borrow and modify elements from pre-existing maps; instead they concocted an entirely new cartographic language with which to convey the limited range of information they felt was relevant, one that proved sufficiently suitable for its purpose to last for 400 years. In each case, like the humble zip or television, the portolan chart and the London Underground Map provided something that people didn’t realise they needed, because the idea they represented did not then exist. But once available, they became indispensable.

The positional accuracy displayed in the Carte Pisane Accepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118) was not a happy accident; it could not have been achieved merely through centuries of trial and error. This thesis argues that one of the seeds out of which the portolan chart grew would have been the realisation that the individualistic and disjointed mental maps made up of pelagic course memories could only be made more accurate through a collaborative process that used a graphic medium to combine them into a single permanent record. That way it became possible to break out of a self-limiting process of knowledge transmission from one generation to the next – without any means of cumulative improvement. Through the pooling of information, a level of precision could be achieved that would be far greater than any individual might have attained. In other words, this essay claims that the charts were only created because they were better than those pilots already had in their heads; hence, their origin depended on a mixture of knowledge and ignorance.

One of the major virtues of the portolan chart was its democratising function. Everybody was granted equal access to the overall knowledge that had previously been held exclusively by experienced sailors. Because it was essentially graphic rather than textual, sailors were not excluded by a literacy barrier.

Where the chart might have been born is an interesting question but currently unanswerable. It was probably a busy port on the west coast of Italy with its extended trading tentacles. From such a place, the seas and islands to the west would have provided sufficient control points for both the hypothetical pelagic diagram and its extension into the open-sea beyond. Indeed, it is possible that the characteristics of that coast actually provided the reason for the charts’ invention, because the Adriatic and Aegean seas have total intervisibility and would have had less need of a hydrographic guide than areas where no land was in sight.

There is no reason to assume that the creator(s) of what is being proposed here as the initial stage of what would become a portolan chart – namely a graphic representation of the network of pelagic courses held in sailors’ memories – already had the concept of a complete chart in their mind. That is highly unlikely. Subsequent imaginative leaps must surely have been required before the further stages were realised: filling in the coastlines and populating them with toponyms, as well as delineating the off-shore dangers.

We can witness the continuation and end of that process of phased improvement in the period between the Carte Pisane and the charts that followed until about 1340. The lack of significant subsequent amendments emphasises both the originality of the original concept and the extent to which the charts must have satisfied their users’ requirements.

It is unlikely that the charts’ creators had seen other maps, and if they had, they clearly found nothing useful in them. The gulf between any of the possible antecedents that have been suggested and the earliest extant portolan chart, the Carte PisaneAccepted as the oldest surviving portolan chart, c.1270, its author and place of origin are unknown. It has been in the Bibliothèque nationale de France since 1839 (Cartes et Plans, B 1118), is visually and conceptually as vast as that dividing the Mediterranean charts from all other cartography of that time and indeed for long afterwards. We also need to remember that perhaps two to three generations divided the creation of the prototype chart, conjecturally at the end of the 12th century, from the Carte Pisane: in other words an extended period for gradual developments which have left no trace.

Since its information was new, personal inspiration must have been involved, perhaps with a ‘eureka’ or ‘lightbulb’ moment. Such an individualistic interpretation is no doubt deeply unfashionable, but is that enough to invalidate it?

P.3.  Purpose and use

A landsman’s map, which stops when it hits the sea, deals with a world of known, recognisable entities, those that can be matched with experience. Likewise, a sailors’ chart depicts the coastlines and the features of navigational relevance for those in the in-shore cabotage trade. But, for the open-sea or pelagic mariners, the requirement was for a map that provided them with the assured relative positions of the harbour they had left and their next planned landfall, along with what might become visible on their long passage. The portolan chart would have taken the helmsman mentally over the horizon so that he could preview whatever land might lie ahead. In that sense it is charting what is un-chartable. Put simply, the portolan charts were navigational charts primarily designed for use out at sea.

The sailors’ gnarled, salty finger-prints were all over the portolan chart from the outset. Perhaps, as has been regularly highlighted in this essay, we are more likely to understand these ‘sailors’ charts’ once we have learnt to appreciate the range and profound depth of the practical, life-preserving skills that seasoned medieval mariners must have possessed (or indeed that some indigenous sailors retain today). It was their maturity and intelligence that crafted a device which would remain in use for four centuries, formed of a mixture of precisely located promontories, formulaic coastal indentations, artificially-shaped islands, and toponyms –in their right order, but usually spaced out evenly, particularly along a crowded coastline.

Close analysis of the portolan charts reveals that the charts were entirely pragmatic. There was never an intention of creating a comprehensive and fully accurate survey of the Mediterranean and Black Sea, and the coastlines north of Bruges and England were left as meaningless generalisations for centuries, since restrictions imposed on Mediterranean shipping rendered that region largely irrelevant.

P.4.  The portolan charts’ place in the history of cartography

The Hereford Mappa Mundi, a near contemporary of the Carte Pisane, is truly medieval in its other-worldly complexity and strangeness, 536 whereas much about the portolan chart is apparently straightforward, even ‘modern’, and immediately recognisable. If we look across the full gamut of map history the portolan chart was ground-breaking in a number of ways. 537  In some respects a marine chart and a topographical map are mirror images of one another. The portolan charts were exclusively concerned with the coastlines but, as an accidental result, they thereby revealed new and far more realistic outer limits for the countries involved. Considered together, the two formats go a long way to providing a full picture.

There is no evidence that the portolan chart’s begetter(s) were much exercised about geographical theories concerning the shape and size of the world, nor how much the chart should reflect and endorse Biblical teaching. Neither do the charts consider the zonal or three-continent divisions of the schematic world maps and mappaemundi, nor the astronomically-fixed positions of the Ptolemaic maps [Powerpoint, Slide 5].

How many earlier maps were created for practical use in the real world? Measured estate and property maps can be traced back to Mesopotamia; the Romans produced large-scale plans (for example of Rome); schematic diagrams would sometimes be included in court documents to illustrate the geographical details of a medieval law-suit; and mineral maps from central Europe are known from the 15th century. But all those examples were local in scope. An outstanding exception are the scaled maps of China, produced from the 3rd century CE onwards, but it is unlikely they were known in Europe. Hence the portolan charts can claim to represent the first demonstration of empirical geometry over a large region, as distinct from mensuration (for example, by the Romans), the astronomical determination of Ptolemy and the ancient Greeks, or the numerous informants providing data for al-Idrīsī’s Charta RogerianaA 3.5 metre wall-map of the world created, in Arabic, by Muhammad al-Idrīsī in Palermo, Sicily for the Norman king Roger II in 1154, and preserved, in the form of 70 sections, in several copies of a manuscript text.

Whereas, Matthew Paris’s strip-road maps of the mid-13th century were diagrammatic, and their content could have been largely conveyed in writing, the slightly older portolan chart can lay claim to the title of the earliest transport or mobility map, and specifically the first whose content and format were designed for a voyage or journey.

P.5.  Rating this essay

Even if some of the conclusions in this essay appear revolutionary, several of the more significant ones had been anticipated. But, for some reason, the dots had never been joined up, perhaps because of an unexamined assumption that the portolan charts’ source would take a textual form.

It is fair to claim that there is now general (though not total) acceptance – as evidenced by repeated quotations throughout the essay from leading portolan-chart investigators – that the charts’ geometry almost certainly derived from memorised pelagic voyages (reported or experienced). Indeed, there is no plausible alternative to a pre-compass, pre-chart navigation lore based on memory and oral transmission. As an extension to that, the growing appreciation of the ubiquity of mental maps makes such a claim here unexceptional.

At the heart of this essay is the assertion that medieval sailors must have closely observed, and then carefully remembered, each open-sea crossing they had made, and that it was that information which was shared and turned into a graphic diagram out of which the portolan chart developed. Furthermore, the fact that al-Idrīsī in 1154 was unaware of the portolan chart – unless that statement can be challenged – confirms a medieval origin. Where paths may still diverge is in alternative explanations as to how those spatial memories were turned into a graphic document: in other words how that gap between memory and chart was bridged.

This essay has gathered up the scattered clues and analogies and, with the aid of logical deduction, constructed what it is hoped is an acceptable overarching thesis. It is for others to judge whether this has solved what has surely been one of the longest-lasting mysteries in the history of cartography and conceivably the most significant of them all. 538 

P.6.  The future

Looking ahead, what might we expect to materialise? Providing that funding continues for archival rebinding programmes, we can hope that more fragments of early charts (and even texts?) may be revealed. When we look at the discoveries of charts that can be assigned to the period before 1400, and have emerged in the comparatively recent past, there is surely a good possibility that more will appear in future. With their first mention in brackets, this is the impressive list from the last 30 years: the Avignon chartA chart fragment focusing on the North Sea, probably very early 14th century, discovered in 2002 in the Vaucluse Archives (Port 01, 3E 54) – for Jacques Mille’s studies on this see the Portolan Chart Bibliography: https://www.maphistory.info/portolanref.html (2015), a chart fragment identified as by the late-14th-century Guillem Soler (2011), the Riccardiana chart The oldest Genoese chart, probably dating from the second decade of the 14th century (Biblioteca Riccardiana, Florence, 3827) (2007, when it was first recognised by Ramon Pujades as being very early), the Lucca chartDiscovered in 2000 in the city archives, this is visually very different from other charts from the 1st quarter of the 14th century (Archivio di Stato, Lucca, Fragmenta Codicum, Sala 40, Cornice 194/1) (2000), and a chart mis-attributed to Vesconte (1992). 539  Given that three of those, the Avignon, Lucca and Riccardiana charts, are among the very earliest, and considering further that the stylistic differences between both those and their other near contemporaries are more noticeable than their similarities, I suspect that the next to emerge may perhaps surprise and confuse us in equal measure.


Table of Contents


For brief summaries see the Conclusions


 

ACKNOWLEDGEMENTS

Besides the use made of his doctoral thesis, I am indebted to Roel Nicolai – my co-author on the separately published study of the mental wind compass – for access to his unpublished database of the pelagic instructions in Lo compasso de navegare.

I also wish to acknowledge the information and insights I obtained in online discussions with those associated with the project in Lisbon investigating 'Medieval and Early Modern Nautical Charts' (MEDEA), under the direction of Joaquim Alves Gaspar.

The help of the following, in their many and varied ways, is recognised with gratitude:

Bruno Almeida, Corradino Astengo, Peter Barber, Michael Barritt, Robbie Campbell, Catherine Delano Smith, Gonçalo Dias, Jean-Charles Ducène, Joaquim Alves Gaspar, Anton Gordieiev, Paul Harvey, Friedrich Hild, Leif Isaksen, Wolfgang Koberer, Sima Krtalic, Henrique Leitão, Arthur MacDivitt, Gregory McIntosh, Jacques Mille, Laurent Monsaingeon, Ana Margarida Nunes, Richard Pflederer, Ramon Pujades, Yossef Rapoport, Luis Robles Macias, Fateme Savadi, Sarah Tyacke, Emmanuelle Vagnon, Thomas Warner

I very much hope that list is complete but with a project spread over four years I may have overlooked some earlier contributions, for which I apologise. I will happily expand the list in the light of post-publication comments. The way I have made use of the suggestions of others is of course my responsibility alone; no-one is to be held responsible for any of the statements in this essay

Finally, special thanks for considerable editorial help from Ljiljana Ortolja-Baird and essential technical assistance from Damien Bove


Table of Contents


 

ENDNOTES

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1. An analysis that proved necessary in order to understand the Charta Rogeriana’s impact on this topic, or lack of it, became so large as to warrant separate publication, see The Charta Rogeriana: a reappraisal of the making of al-Idrīsī’s world map of 1154 and its dissemination.

2. The term ‘prehistory’ may be technically incorrect since that is deemed to end with the wide adoption of writing. Clearly that is not the case with the portolan charts. However, its use seems defensible because we know nothing certain about them – whether from textual records or physical fragments – prior to the Carte Pisane.

3. See also the Liber; and for further background E.1a. 13th-century textual sources: the Liber. On the dating see J.1. The charting of the Black Sea.

4. See also Lo compasso de navegare; and for further background E.1b. 13th-century textual sources: Lo compasso de navegare.

5. Tony Campbell, 'Portolan Charts from the Late Thirteenth Century to 1500', in J.B. Harley & David Woodward (eds) The History of Cartography, Volume 1 (Chicago University Press, 1987), 371-463, at 380.

6. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5) largely ignored the origin issue, which was handled instead in an interpolated section by David Woodward; whereas Ramon J. Pujades i Bataller, Les cartes portolanes: la representació medieval d'una mar solcada [in Catalan and Spanish, with English text titled 'Portolan charts: the medieval representation of a ploughed sea', 401-526]. (Barcelona: Institut Cartogràfic de Catalunya; Institut d'Estudis Catalans; Institut Europeu de la Mediterrània; Lunwerg, 2007), devoted his entire final chapter to it.

7. Pujades, Les cartes portolanes (see note 6), 444-46, notes that "Inventories abound with references to old, torn charts, and narrative and poetic sources with allusions to their use on ships".

8. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 443a; Jean Richard noted that although comments from travellers start to appear in the late 14th century, little notice was taken of sailors: ‘Les gens de mer vus par les croisés et par les pelèrins occidentaux au Moyen Age’, in Le genti del mare Mediterraneo (Naples, 1981), 341-55.

9. Pujades, Les cartes portolanes (see note 6), 506a.

10. Roel Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts, Doctoral thesis, University of Utrecht (Science), March 2014, 410. An amended version was published as The Enigma of the Origin of Portolan Charts. A Geodetic Analysis of the Origin of Portolan Charts (Leiden; Boston: Brill, 2016). The quotations and page numbers are taken from the 2014 thesis because that text is conveniently online.

11. Ibid., 412.

12. Joaquim Alves Gaspar, 'The Liber de existencia riveriarum (c.1200) and the Birth of Nautical Cartography'. Imago Mundi, 71:1 (2019): 1-21.

13. H.1. ‘Pointers to the likely period of the portolan charts’ creation’.

14. Théorie de l’invention (1881).

15. No effort was made to determine precisely when speculation started about the charts’ origin but it is likely to have been by the mid-19th century if not earlier.

16. David Álvarez Jimenez Correio & Sergio Remedios Sánchez Correio, ‘Men of Sea. The making of an Identity’, Revista Diálogos Mediterrânicos, 7 (December 2014): 128-40, see 139.

17. Christer Westerdahl, ‘Odysseus and Sindbad as metaphors: On some cross-disciplinary approaches to the lore of the seas’ (2013 or later, based on a 2009 talk), 33-65, at 33.

18. The self-employed London drivers in their distinctive black cabs, despite being competitors, always make way for one another, hence saving time – part of the code of practice they learn doing the ‘Knowledge’.

19. See F.1. ‘How were distances measured?’. The rectification process posited for drawing together the pelagic courses could not have occurred without that common measure, at least for the Mediterranean, since the differently scaled fringe areas of the Atlantic and Black Sea were not initially included, and must have been bolted-on later without those discrepancies being realised.

20. For the separate analysis, partly contributed by Roel Nicolai, see The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use (2020).

21. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 410.

22. Jonathan Lanman, On the origin of portolan charts. Hermon Dunlap Smith Center Occasional Publications 2 (Chicago: Newberry Library, 1987).

23. See, for comments about the imprecision of those directional statements, G.1d. ‘Settling the priority question’.

24. Gaspar, 'The Liber de existencia riveriarum (c.1200) and the Birth of Nautical Cartography' (see note 12), 2.

25. See A.3a. The Book of Curiosities.

26. See F.3. The ‘Sub-charts' hypotheses.

27. See A.3b. ‘al-Idrīsī’s Charta Rogeriana of 1154’.

28. For a good introduction to the different map types referred to above, see P.D.A. Harvey, Medieval Maps (London: British Library, 1991).

29. See ’The Innovations’.

30. Pietro Janni referred to those who “take for granted the thought-world of easy, habitual, map-literacy” (1984, quoted by Matthew Boyd Goldie, ‘An Early English Rutter: The Sea and Spatial Hermeneutics in the Fourteenth and Fifteenth Centuries’, Speculum, 90/3 (July 2015): 702.

31. On which see Harvey, Medieval Maps (see note 28).

32. See 'The Charta’s possible antecedents'.

33. Pujades, Les cartes portolanes (see note 6), 506a, 420 & 513b respectively.

34. Patrick Gautier Dalché, Carte marine et portulan au XIIe siècle: le "Liber de existencia riveriarum et forma maris nostri Mediterranei" (Pise, circa 1200) (Rome: École française de Rome: distributor, Paris: Boccard, 1995), 81 [available Online], although that rested on a now-superseded translation of the word ‘gradiens’ – see I.2a. ‘Gradiens’.

35. See E.4. ‘The pelagic statements listed in the Liber.

36. “There is not a single ancient text written by a sailor” – Correio, ‘Men of Sea. The making of an Identity’ (see note 16), 139.

37. Yossef Rapoport & Emilie Savage-Smith. Lost maps of the Caliphs: Drawing the world in eleventh-century Cairo (University of Chicago Press, 2018), 151.

38. Some fellow researchers maintain this argument privately, though not yet, I think, in print.

39. Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 125-53. See the full digitised text and the now withdrawn website.

40. Ibid., 153.

41. Ibid., 130.

42. Ibid., 147.

43. Ibid., 148.

44. Ibid., 150.

45. Ibid., 125-26. Rapoport & Savage-Smith note that the descriptions of the bays in southwestern Turkey is “so systematic you could imagine it translated into a diagram of the curves of the Anatolian coast”, and the Peloponnesus sequence was treated in a similar fashion.

46. Ibid., 151.

47. The Ebstorf and Hereford world maps are later, dating from the 13th century, as does the earliest surviving Greek manuscript of Ptolemy’s Geographia.

48. The Charta Rogeriana: a reappraisal of the making of al-Idrīsī's world map of 1154 and its dissemination (2020).

49. This, the following paragraph, and a few other later passages, are repeated in the separate Charta Rogeriana essay.

50. I owe this point to Richard Pflederer.

51. Private communication from Leif Isaksen, 11 August 2019.

52. Tarek Kahlaoui, Creating the Mediterranean: Maps and the Islamic Imagination (Leiden: Brill 2018) 165-6.

53. Jean-Charles Ducène, The Encyclopaedia of Islam. Three (Brill: Leiden & Boston, 2018), 91-99, at 95-6.

54. Though there are undoubted similarities between its treatment of the mountain ranges and those that were introduced on Majorcan charts from 1330 onwards – perhaps a reflection of a later discovery of the Charta in the Christian West?

55. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 10b. “The east–west orientation of the Adriatic Sea on al-Idrīsī ’s depiction, probably imported from a Ptolemaic-based source, and the crudity of his representation of the northern coast of Africa, also point away from any other known traditional map as the source of the Liber’s information.”

56. J.B. Harley, in The History of Cartography, Volume 1, 1.

57. M.R. O’Connor, Wayfinding: the science and mystery of how humans navigate the world (New York: St Martin’s Press, 2019). Available as an Audiobook.

58. Ibid., 46-7. Anthropologists make a similar distinction, see 207.

59. Anita Devineni, ‘How the brain encodes Space and Place’, online Outreach article, November 2016. (I am grateful to Ana Margarida Nunes for that reference).

60. For further reading on this subject see Russell A. Epstein (et al.), ‘The cognitive map in humans: Spatial navigation and beyond’, Nature Neuroscience, 2017 Oct 26; 20(11): 1504–1513 (a literature overview, with 150 citations); and Reginald G. Golledge, ‘Human wayfinding and cognitive maps’, in Marcy Rockman and James Steele (eds) Colonization of unfamiliar landscapes: The archaeology of adaptation (London & New York: Routledge, 2003), 50-68).

61. John Edward Huth, The Lost Art of Finding Our Way (Belknap/Harvard University Press, 2013), 29.

62. Cited in O’Connor, Wayfinding (see note 57), 5 & 262.

63. Psychological Review, 55, no.4 (1948): 189-208.

64. O’Connor, Wayfinding (see note 57), 88-91. In this context it is reasonable to consider the navigational skills of birds. On this see Jennifer Ackerman’s summary of recent research, The Genius of Birds (London: Corsair, 2016), for her Chapter 7: ‘A mapping mind: Spatial (and temporal) ingenuity’ (pp. 227-76). Despite the small size of their brains, the navigational ability of some birds is hugely more developed than our own. Among her observations is the similar way that the brains of humans and birds (who diverged 310-330 million years ago) are arranged for the connectivity necessary for navigation (274-5); in each case, the hippocampus contains both mental maps and memories (252). Other indicators: greater spatial ability is marked by an enlarged hippocampus (253); they use a wide range of cues including the sun (for which the internal clock possessed by all birds is essential), the stars (particularly the North Star) and responses to magnetic fields not yet fully understood (239); while smell (via the olfactory bulb found in all vertebrates) is particularly important for bird navigatio (269).

65. Ibid., 15.

66. Ibid,, 168-70.

67. Seen 15 August 2019 – unsourced.

68. Maps and History: Constructing Images of the Past (New Haven and London, Yale University Press, 1997), 1 – described thus in Imago Mundi, 55 (2003): 124, note 1.

69. David Woodward & G. Malcolm Lewis, in The History of Cartography Volume 2:3. Cartography in the Traditional African, American, Arctic, Australian, and Pacific Societies, 3-4.

70. O’Connor, Wayfinding (see note 57), 235-47.

71. On the Black Cab’s ‘Knowledge’ see E.A. Maguire, R.S.J. Frackowiak & C.D. Frith, ‘Recalling routes around London: Activation of the right hippocampus in taxi drivers’, The Journal of Neuroscience 17 (18) (1997): 7103–7110; and Ian Beetlestone, ‘The history of London's black cabs’, The Guardian, 12 December 2012.

72. O’Connor, Wayfinding (see note 57), 52, 268, 273; and Rebecca Campbell, ‘Spatial Orientation and the Brain: The Effects of Map Reading and Navigation’, GIS Lounge, 8 March, 2013.

73. O’Connor, Wayfinding (see note 57), 147-9, 160, 185-6, 200-06.

74. Ben Finney, ‘Nautical Cartography and Traditional Navigation in Oceania’, in The History of Cartography Volume 2:3. Cartography in the Traditional African, American, Arctic, Australian, and Pacific Societies (Chicago, 1998), 443-92. See particularly 454-75 for the astronomical and mathematical calculations required of the Caroline islanders, which are far more complex than anything that would have been encountered by medieval mariners.

75. Ibid., 443; see also 460.

76. Ibid.

77. Ibid., 487. See also O’Connor, Wayfinding (see note 57), 239-40.

78. Ibid., 461.

79. Some of the maps were drawn out, others carved in wood to show the coastal indentations. Cited by O’Connor, Wayfinding (see note 57), 38. See also Claudia Aporta, ‘The Trail as Home: Inuit and their pan-Arctic network of routes’, Human Ecology, 2009.

80. Finney, ‘Nautical Cartography and Traditional Navigation in Oceania’ (see note 74), 459.

81. O’Connor, Wayfinding (see note 57), 14.

82. Ibid., 108.

83. Barry Cunliffe, On the ocean: the Mediterranean and the Atlantic from prehistory to AD 1500 (Oxford University Press, 2017), 558, 61.

84. Correio, ‘Men of Sea. The making of an Identity’ (see note 16), 129.

85. On ancient navigation and routes see particularly: Stefano Medas, De Rebus Nautica. L’Arte della navigazione nel mondo antica (Rome: L’Erma di Bretschneider, 2004), and Pascal Arnaud, Les routes de la navigation antique. Itinéraires en Méditerranée (Paris: Éditions Errance, 2005).

86. Danny Lee Davis, 'Commercial Navigation in the Greek and Roman World', PhD dissertation, University of Texas at Austin, 2009 ('Introduction'). For an overview of trade voyages in classical and, to a lesser extent, medieval times, see Pascal Arnaud, ‘Ancient sailing-routes and trade patterns: the impact of human factors’, in: Damian Robinson & Andrew Wilson (eds), Maritime Archaeology and Ancient Trade in the Mediterranean OCMA Monograph 6, Oxford Centre for Maritime Archaeology, 2011 (61-80 = 59-78 in the Academia version); and Terrance M.P. Duggan, 'From mid-October to the end of March – voyaging in the Medieval Mediterranean', Cedrus III (2015): 277-310, in which he argues that "one can regard the legal prohibition placed upon winter sailing as a Medieval legal fiction, rather than there being in practice a closed Mediterranean during the months from mid-October to mid-March during the course of these seven centuries [7th-end 14th], with the probable exception of fishing boats and fishing fleets".

87. ‘Between Venice and the Levant: Re-evaluating maritime routes from the fourteenth to the sixteenth century’. The Mariner's Mirror, 96 No.3 (2010): 264-94, at 264, supported by a list of almost 200 vessels. See also Pascal Arnaud, “Every source underlines that sailing the blue sea was common as early as the time of Homer”: 'Ancient Mariners Between Experience and Common Sense Geography', in: Klaus Geus & Martin Thiering (eds.) Features of common sense geography: Implicit knowledge structures in ancient geographical Texts (Münster et al.: LIT Verlag, 2014) pp.39-68, at 42.

88. Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 182.

89. Carmen Tania Macleroy Obied, ‘Rethinking Roman perceptions of coastal landscapes: a case-study of the Levant’. PhD thesis, University of Southampton (Archaeology), 2016, 10 [= 21 online].

89a. Arnaud, ‘Ancient Mariners’ (see note 87), pp.39-40.

90. On pilgrimage routes see David Jacoby, ‘Evolving Routes of Western Pilgrimage to the Holy Land, Eleventh to Fifteenth Century: an Overview’, in: Klaus Herbers / Hans Christian Lehner (eds) Unterwegs im Namen der Religion II / On the Road in the Name of Religion II. Wege und Ziele in vergleichender Perspektive – das mittelalterliche Europa und Asien /Ways and Destinations in Comparative Perspective – Medieval Europe and Asia (Steiner Verlag, 2014), 75-97.

90a. See B.2a. 'The workings of spatial orientation'.

91. Quoted in David W. Waters, The art of navigation in England in Elizabethan and early Stuart times (London: Hollis & Carter, 1958), 15.

92. Cunliffe, On the ocean: the Mediterranean and the Atlantic from prehistory to AD 1500 (see note 83), 68.

93. Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 240.

94. Ibid., 77.

95. Ibid., 78.

96. See ’The mental wind compass’.

97. Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 236.

97a. See D.3. 'The magnetic compass'.

97b. See F.1b. 'Measuring distance in terms of time or miles'.

98. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 117, and Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 441-43.

99. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 121-27, which gives a thorough explanation and a review of the literature.

100. See Andrew Crowe, ‘Nature’s Navigators’, Pukorokoro Miranda News, 2019. “A summary of what is currently known of the diverse sensing abilities that migrating animals use to navigate, with a review of the types of information that traditional Pacific navigators were able to glean from them”. On the value of birds for help in fixing a position – in relation to their identity and known diurnal activity and flying range – see James Hornell, ‘The role of birds in early navigation’, Antiquity 20 (1946): 142-9; and David Henry Lewis, We, the Navigators: The Ancient Art of Landfinding in the Pacific (originally published in 1972), e.g. 208-15, 389-90 (partly available via Google Books); also Finney, ‘Nautical Cartography and Traditional Navigation in Oceania’ (see note 74), 443, 460.

101. Cunliffe, On the ocean: the Mediterranean and the Atlantic from prehistory to AD 1500 (see note 83), 64.

102. Ibid., 67.

103. Interestingly, “A sense of smell may have evolved to help people find their way around, an idea called the olfactory spatial hypothesis… Scientists have connected both skills to the same areas in the brain”: Laura Sanders, ’People who have a good sense of smell are also good navigators’, Science News, 16 October 2018. The importance of olfactory clues for unaided navigation seems not to have been adequately investigated.

103a. See D.2. 'The mental wind compass'.

104. Cunliffe, On the ocean: the Mediterranean and the Atlantic from prehistory to AD 1500 (see note 83), 558.

105. See B.3c. ‘Indigenous examples of mental navigation maps’.

106. Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 17.

107. Ibid., 21. “The Mediterranean abounds in islands. The figure would well surpass two thousand if every islet, isle and island proper were counted … Of islands proper (i.e. those large enough to sustain human habitability), the Mediterranean boasts some 115".

108. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 10 and Fig. 6. On that issue see further, F.2. ‘The importance of landward visibility’.

109. Konrad Kretschmer, Die italienischen Portolane des Mittelalters: Ein Beitrag zur Geschichte der Kartographie und Nautik. Veröffentlichungen des Instituts für Meereskunde und des Geographischen Instituts an der Universität Berlin, vol. 13 (Berlin, 1909; reprinted Hildesheim: Georg Olms, 1962), 358. Harvard University has mounted a scanned version of this and other portolani, allowing you can search for any word and enlarge the retrieved page (though there may be access problems from some locations). Similarly, the self-styled ‘Venetian gentleman’, Bernardino Rizo, claimed in his printed portolano of 1490 to have seen everything he described (Kretschmer, 552). Jacques Mille (private communication 24 May 2020) found evidence from France’s south coast to corroborate Benincasa’s claim for originality.

110. See B.3b1. ‘London’s Black Cab drivers’.

111. See B.3c. ‘Indigenous examples of mental navigation maps’.

112. “Every time I learn something new, it pushes some old stuff out of my brain”, Homer told Marge. ”Remember when I took that home wine-making course and I forgot how to drive?” The term was coined by David Hawkins in 2015.

113. Stanislas Dehaene, Reading in the brain; the new science of how we read (Penguin Books, 2009), 210-12. I owe this reference to Robbie Campbell.

114. Mo Costandi, ‘The Homer Simpson effect: forgetting to remember’, The Guardian, 24 April 2015, citing Maria Wimber, et al. ‘Retrieval induces adaptive forgetting of competing memories via cortical pattern suppression’, Nature Neuroscience, 18 (2015): 582–89.

115. Cunliffe, On the ocean: the Mediterranean and the Atlantic from prehistory to AD 1500 (see note 83), 69.

116. Ibid., 557; on which see also C.1. ‘Navigation in the Ancient World’.

117. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 347.

118. Pujades, Les cartes portolanes (see note 6), 510b, note 58, citing Lanman, On the origin of portolan charts (see note 22). In addition, that account of a gradual, collective refinement closely mirrors the hypothesis being expounded here.

119. Joaquim Alves Gaspar & Henrique Leitão. 'Early Modern Nautical Charts and Maps: Working Through Different Cartographic Paradigms', Journal of early modern history 23 (2019): 1-28, on 27-28.

120. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 10a.

121. See B.3b.1. ‘London’s Black Cab drivers’, about the enlarged hippocampus that showed up in brain scans of London Black Cab drivers.

121a. See C.2c. ‘Sea signs’.

122. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 10b, Note 56.

123. Pujades, Les cartes portolanes (see note 6), 511a.

124. The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use (2020).

125. See, for example, Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 380-4.

126. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 13; also personal communication 16 February 2019.

127. Ibid., 8b.

128. Ibid., 13-15. There is an English version of the Peregrinus text; see also, for the full edition: L. Surlese & R. B. Thomson (eds), Petrus Peregrinus de Maricourt, Opera. Epistula de Magnete. Nova Compositio Astrolabii Particularis (Pisa: Scuola Normale Superiore, 1995). (I owe this link to Corradino Astengo).

129. Julian A. Smith, ‘Compass, Magnetic’, in John Block Friedman, et al. (eds), Trade, Travel, and Exploration in the Middle Ages: An Encyclopedia (Routledge, 2000), 123 – available online via Google Books.

130. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 343.

131. Pujades, Les cartes portolanes (see note 6), 444a.

132. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 15.

133. Nikola Tesla, ‘Reference to Compass in 13th Century Poem’, The Science News-Letter 34 (no. 15, October 8, 1938): 238 (for that translation) and also John Orr (ed.), Les Œuvres de Guiot de Provins (Manchester University Press, 1915), 30 (for the original old French). Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 15, offers a different passage from Guyot de Provins, in a translation from old French.

134. "Acus ferrea postquam adamantem contingerit, ad stellam septentrionalem, quae velut axis firmamenti aliis vergentibus non movetur, semper convertitur. Unde valde necessaria est navigantibus in mari". Jacques Bongars (ed.) Gesta Dei per Francos (1611) I, 1106.

135. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 13b and Fig. 5.

136. As E.G.R. Taylor explained, ”The needle (as it was supposed) always turned towards the North Star, and did do, as it seemed, by mystic sympathy”, The Haven-finding Art (London: Hollis & Carter, 1956), 100.

137. Yet Gaspar’s analysis, in 'The Liber de existencia riveriarum (c.1200)’ (see note 12), Table 1 and p.10, indicates greater degrees of precision.

138. See Sarah O’Connor, 'A brief, heavily historiographical survey of maritime technology in use during the Crusades, with attention paid to the effects of methods of production and predominant weather patterns in the Mediterranean. Paper written for an undergraduate class at the University of New Hampshire in 2005'. That article cited Barbara M. Kreutz, ‘Mediterranean Contributions to the Medieval Mariner’s Compass’, Technology and Culture, 14, 3 (July 1973): 367-83, at 74, who considered that the instruments were in common usage by 1315.

139. Helen M. Wallis & Arthur H. Robinson (eds) Cartographical Innovations: an international handbook of mapping terms to 1900 (Map Collector Publications, 1987), 166.

140. On which see The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use (2020).

141. The earliest known correction of the Mediterranean tilt can be seen on a chart by Diogo Ribeiro (1525); the 1557 Battista Testarossa navigational manual in the Royal Geographical Society (with commentary to the facsimile by Richard Pflederer); and a portolan chart by Bartolomeo Crescenzio (1596). A few later chartmakers dealt with the magnetic declination problem by including paired general charts of the Mediterranean: one following the traditional form, the other swung through 9 degrees, see for example, Simonetta Conti, ‘Le carte nautiche "doppie" della famiglia Olives-Oliva', in Momenti e problemi della geografia contemporanea. Atti del Convegno Internazionale in onore di Giuseppe Caraci geografo storico umanista. Roma, 24-25-26 novembre 1993. Centro italiano per gli studi storico geografici (1995), 493-510 (discussing charts of 1616-22). Another example occurs in the consecutive pages of an atlas by João Teixeira Albernaz of 1630 in the Library of Congress, whose two versions deal with "por alturas" (by heights = latitudes) and "por derrotas" (by routes) respectively – with thanks to Joaquim Alves Gaspar and Richard Pflederer for these references.

142. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 18, note 21.

143. Personal communication 11 February 2020, based on a paper given at the 28th ICHC, Amsterdam 16 July 2019.

144. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 13b; and also E.5b. ‘Why the Liber’s pelagic statements must have been copied from a cartographic document’.

145. Ibid.

146. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 67.

147. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34).

147a. Pujades, Les cartes portolanes (see note 6), 519, note 76.

148. David Jacoby, 'An Unpublished Medieval Portolan of the Mediterranean in Minneapolis', in: Ruthy Gertwagen & Elizabeth Jeffreys (eds), Shipping, Trade and Crusade in the Medieval Mediterranean: Studies in Honour of John Pryor (Farnham: Ashgate, 2012), 72.

149. See H.2d. ‘Establishing a terminus ante quem for the portolan chart’.

150. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 6 (with my italics). The frontispiece to Gautier Dalché’s edition of the Liber illustrates the end of the Contents and the beginning of the ‘Prologue’.

151. Ibid.

152. Ibid., 16.

153. Ibid., 6.

154. Pujades, Les cartes portolanes (see note 6), 516b.

155. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 10.

156. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 6.

157. Ibid.

158. Ramon Pujades, 'Explotación económica y aprehensión intelectual del espacio en la baja edad media y el Renacimiento: el potencial informativo de la cartografía y los textos técnicos de carácter geográfico para los historiadores de la economía', in: Francesco Ammannati (ed.) Dove va la storia economica? Metodi e prospettive. Secc. XIII-XVIII / Where is economic history going? Methods and prospects from the 13th to the 18th centuries. Atti della "Quarantaduesima Settimana di Studi", 18-22 aprile 2010 (Florence: Firenze University Press / Fondazione Istituto Internazionale di Storia Economica "F. Datini", 2011), 267.

159. Ramon Pujades, 'The Pisana Chart: really a primitive portolan chart made in the 13th century?', Cartes et géomatique, 216 (June 2013): 18 (paper delivered at the international conference, 'D'une technique à une culture: les cartes marines du XIIIe au XVIIIe siècle', Paris 3 December 2012), However, that information has been reinterpreted, see ‘Updates’ (26 December 2018) at the head of the Carte Pisane essay.

160. Alessandra Debanne, Lo compasso de navegare. Edizione del codice Hamilton 396 con commento linguistico e glossario (Brussels, etc.: Peter Lang for the Gruppo degli italianisti delle Università francofone del Belgio, 2011), 29.

161. Andrea Bocchi, 'Per peleio e per estarea. Su una recente edizione del Compasso de navegare', Lingua e Stile 46 (2011): 275. That said, the olivole form was not replaced by villa franca on the portolan charts until the 1455 Pareto chart, so it would seem that the name change had little impact.

162. For comments on their divergent toponymy see ‘Carte Pisane. Names on the two early portolani related to the those on the four charts’.

163. For details of Lo compasso’s navigational information see ‘Mental Wind compass: Who would have needed to use the wind compass?’.

164. Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 189.

165. Via Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 77, citing The Corrupting Sea: A Study of Mediterranean History (Oxford: Blackwell, 2000).

166. See Kretschmer, Die italienischen Portolane des Mittelalters (see note 109), 358-420.

167. Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 138, 148.

168. Tarek Kahlaoui, Creating the Mediterranean: Maps and the Islamic Imagination (Brill, 2018), between 142-67.

169. Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 249.

170. See L.1b. ‘Orally transmitted pelagic descriptions’.

171. Pujades, Les cartes portolanes (see note 6), 465a.

172. See L.3a. ‘Would medieval sailors have been literate?’.

173. See F.3. ‘The sub-charts hypotheses’ for Ramon Pujades’s refutation of the suggestion that hypothetical documents – in that case local charts – would have been in circulation.

174. Called variously sailing directions, pilot books, mariner’s handbooks, port approach guides, coast pilots, notices to mariners, etc.

175. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 286-7.

176. For detailed analysis of the respective pelagic statements, see ’The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use’ (2020).

177. Though not, for example, one obvious instance very close to the Sicilian coast, Mt Etna, whose visibility from a great distance must have made it a useful navigation aid. Perhaps it was considered too obvious to be mentioned in that respect in the early pilot books, but the Liber has three references to the volcano, including a brief note (Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 174, line 2223). Lo compasso does not apparently mention it at all, and the scale of the charts themselves did not provide space for Etna’s inclusion.

178. See I.3. ‘What might such a pelagic diagram have looked like?’

179. See K.1d. ‘The charts main elements: Islands’.

180. Gaspar, 'The Liber de existencia riveriarum (c. 1200)’ (see note 12), 4 and, for a map, fig. 4.

181. Ibid.

182. Ibid., 205-19 for the full list of transfretus routes, and, for a map, fig.7.

183. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 305.

184. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 4 & fig. 7.

185. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 205-19. Gautier Dalché was of necessity using Bacchisio Raimondo Motzo’s 1947 edition of Lo compasso, which has since been superseded by Alessandra Debanne’s of 2011 (see note 160).

186. Admittedly, 870 of Lo compasso’s distances are of less than 50 miles – private communication from Roel Nicolai, October 2019, but that applies to the Liber as well, where the figure can occasionally go down to a mere 10 miles.

187. ’Comparison of the 'Precursor' and 'Antecedent' names on two 13th-century portolani and four supposedly very early anonymous charts’: Table B. For comments on their divergent mileage figures, see also E.5d. The discrepancies between the stated pelagic distances in the Liber and Lo compasso.

188. The 1490 Rizo portolan still named them pieleghi, see Kretschmer, Die italienischen Portolane des Mittelalters (see note 109), 420-552.

189. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), Figs 4 & 7.

190. Indeed it is argued that there may have been few precisely defined routes anyway, see C.2a. ‘Pre-knowledge of the route.

191. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 44, although he suggested this might represent a synthesising of separate partial traverses; see also Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 8. The comment about fictitious overland routes applies also to Lo compasso on which see Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 303-9.

192. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 10-11.

193. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 31, 36, 44, 80.

194. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 347.

195. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 6.

196. Ibid, Fig. 7.

197. Ibid.

198. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 206, 215 and three instances on 219.

199. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 348. For more on the linked dating of the Liber and the portolan chart, see H.2d. Establishing a terminus ante quem for the portolan chart.

200. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 13; however, it must be noted that some of the directions did appear to derive from readings taken with a magnetised needle. By contrast, the bearings on the Carte Pisane of c.1270 can be shown to have been uniformly obtained with a magnetic compass.

201. Ibid., 14, Fig. 7.

202. In the early 13th century, before the Black Sea and Atlantic coast had been added to the portolan chart – on which see J.1. ‘The charting of the Black Sea’ – there would have been just a single Mediterranean scale to deal with, not three.

203. Might that be what the Liber’s author meant by ‘calculations’ (rationabiliter), see Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 4b & 6b. The Liber and Lo compasso had different rounding up rules, see F.1. How were distances measured?.

204. On the language used by the Liber’s author to describe the bearings see ‘Mental Wind Compass: The Liber’s wind statements’.

205. When applied to Lo compasso – which had both numerous tracks and a much more elaborate wind compass – those procedures would have required considerable concentration for a single person, requiring familiarity with the full extent of the wind compass. Perhaps in that case the author had a helper for extracting the information or alternatively an amanuensis to transcribe from his dictation.

206. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), Appendice III, 205-19.

207. John Kenneth Hyde, 'Navigation of the eastern Mediterranean in the fourteenth and fifteenth centuries according to pilgrims' books', in: H.M. Blake, T.W. Potter & D.B. Whitehouse (eds) Papers in Italian Archaeology 1. BAR Supplementary Series 41 (vol.2) (1978), 521-39, at 522.

208. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 8 & 13.

209. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 216-7; see also E.5d. ‘The discrepancies between the stated pelagic distances in the Liber and Lo compasso.

210. Pujades, Les cartes portolanes (see note 6), 417-18.

211. Dirk Schlimm & Hansjörg Neth, ‘Modeling Ancient and Modern Arithmetic Practices: Addition and Multiplication with Arabic and Roman Numerals’, in V. Sloutsky, B. Love & K. McRae (eds.), Proceedings of the 30th Annual Meeting of the Cognitive Science Society (Austin, Texas: Cognitive Science Society, 2008), 2097-2102. (I owe this reference to Henrique Leitão).

212. Cunliffe, On the ocean: the Mediterranean and the Atlantic from prehistory to AD 1500 (see note 83), 67.

213. Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 133.

214. Lionel Casson, ‘Speed under sail of ancient ships’, Transactions of the American Philological Association, 82 (1951): 136-48, at 139. On this issue see also Arnaud, ‘Ancient Mariners’ (see note 87), “From time to distance”, pp.42-7.

215. R.T. Balmer, ‘The operation of sand clocks and their medieval development’, Technology and Culture, 19, 4 (Oct. 1978): 615-32.

216. See E.5. ‘The real meaning of the Liber’s ‘pelagic’ statements’.

217. See I.1. ‘Inadvertent triangulation’.

218. Pujades, Les cartes portolanes (see note 6), 204-9, 478a – though of course these are modern calculations, unrecognisable to a medieval sailor.

219. For calculations based on data in Lo compasso, see Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), ‘Interlude on the calculation of the length of the portolan mile’, 313-16 and 347. It also seems unclear whether there might have been different versions for use on land or on sea, just as today we have [land] miles and nautical miles.

220. See Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 228, for the historiography of this topic: the difference between the Atlantic and Mediterranean (Wuttke 1871), and between the Mediterranean and the Black Sea, see James E. Kelley, Jr, 'The Oldest Portolan Chart in the New World', Terrae Incognitae: Annals of the Society for the History of Discoveries, 9 (1977): 46-8.

221. Paper delivered at the Second International Workshop on the Origin and Evolution of Portolan Charts, Lisbon 7-8 June 2018.

222. Roel Nicolai, Analysing MapAnalyst and its application to portolan charts’, e-Perimetron, 13:3 (2018): 15-16.

223. See J.1. ‘The charting of the Black Sea’.

224. This was the conclusion of Ramon Pujades, Les cartes portolanes (see note 6), 511a.

225. Indeed, the overstated latitudinal extent of the Aegean seems not have been corrected until the 16th century.

226. On the refuted suggestion that the twin scales on the 1403 Francisco Beccari chart – ‘duitse mylen’ and ‘spa[n]se mylen’ – are original rather than from a later century, see the comments under ‘Latitude scale’ in: Portolan charts from the late thirteenth century to 1500. Additions, Corrections, Updates.

227. On which see The Charta Rogeriana: a reappraisal of the making of al-Idrīsī's world map of 1154 and its dissemination (2020).

228. Pujades, Les cartes portolanes (see note 6), 514b.

229. See F.3. ‘The sub-charts hypotheses’.

230. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 10 & Fig.6.

231. For coastal mountains, Google Earth 3D view and its associated photographs gives a useful overview of those surrounding the Mediterranean.

232. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 10. He explained, in an email of 15 May 2019, how the diagram was developed: “The calculation of the visibility areas was made considering the surface relief around the Mediterranean, not only the coastlines. A digital terrain model of the area was used, containing the elevations in all nodes of a quite dense geographical grid (including several thousand points in islands). Furthermore an average height of the observer above sea level of 3 meters was considered, as well as the effect of refraction in the atmosphere.”

233. These zones are effectively divided into seven: respectively, west and east of Sardinia, the eastern Mediterranean and Black sea, both divided into two areas, and the Sea of Azov.

234. For a suggested reconstruction of the process that turned those accumulated sightings in the grey zones into a geometric diagram see I.1. 'Inadvertent Triangulation'.

235. As was expressed most forcefully by Roel Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 412.

236. Hermann Wagner, ‘Das Rätsel der Kompaßkarten im Lichte der Gesamtentwicklung der Seekarten’, Verhandlungen des XI. Deutschen Geographentages, in Bremen (1895), 66-87: ("die schöpferischen Leistungen der italienischen Kartographen zunächst auf die Berichtigung und Zusammenfügung älterer Karten der Einzelbecken zu einem Gesamtbild”.) I owe this reference to Wolfgang Koberer.

237. Periplus: an essay on the early history of charts and sailing-directions (Stockholm: Norstedt, 1897), 45 – but Nordenskiöld based it on a misinterpretation that the simplified extracts from a portolan chart in Dati’s ‘La Sfera’ (15th century) were copies of the supposed precursor sub-charts, on which see Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 383-4.

238. Kretschmer, Die italienischen Portolane des Mittelalters (see note 109), 95.

239. [Campbell], ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 388, in a section (387-88) written by David Woodward. That investigation was partly based on, and then carried further, in Scott Loomer’s 1987 thesis: 'A cartometric analysis of portolan charts: a search for methodology'. Doctoral dissertation, University of Wisconsin, 1987.

240. For the relevant publications see the summary list, referring to the Bibliography’ for the details.

241. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 402.

242. Ibid, 229, Fig. 7.8; see also Nicolai, ‘Analysing MapAnalyst and its application to portolan charts’ (see note 222), 15-16.

243. Personal communication, 12 March 2020.

244. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 402.

245. Woodward, in Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 239), 387.

246. A close reading of the portolani transcriptions might provide a partial answer to that question, see Kretschmer, Die italienischen Portolane des Mittelalters (see note 109), 235-552.

247. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), illustrated on 286-7.

248. Pujades, Les cartes portolanes (see note 6), 511a.

249. See M.1. ‘The varied purposes of the portolan charts and how they were used’.

250. See the relevant passage in M.1c. ‘The portolan charts’ limitations’.

251. See 'Cartographic innovations by the early portolan chartmakers (and subsequent developments)’.

252. “In the island-rich Aegean nearly all of the islands can be sighted from some adjacent island or mainland area on the clearest of days.” Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 22.

253. Kretschmer, Die italienischen Portolane des Mittelalters (see note 109), 95.

254. Lanman, On the origin of portolan charts (see note 22), 5-21.

255. See E.5b. 'Why the Liber’s pelagic statements must have been copied from a cartographic document'.

256. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 16. Despite his forceful statement, with which I agree, it is important to refute the portolano-first argument.

257. But see doubts as to the way that those distances were measured in the portolani: G.1d. ‘Settling the priority question’.

258. On which see F.3.‘Sub-charts hypotheses’.

259. On shortcomings in Jonathan Lanman’s attempt to do that see Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 2, note 9.

259a. Ibid., Fig.7, for a modern example.

260. On that see A.2. ‘Why is there a widespread assumption in favour of a textual origin for the portolan chart?’.

261. Nicholas C. Vella. ‘A Maritime Perspective: Looking for Hermes in an Ancient Seascape’, in: J. Chrysostomides, J., Dendrinos, Ch. and Harris, J. (eds), The Greek Islands and the Sea, Camberley (Surrey): Prophyrogenitus and Hellenic Institute, Royal Holloway, University of London (2004), 33-57, at 52.

262. The Liber’s author refers to his ‘imperfect memory’, see Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 6.

263. e.g., Lo compasso’s treatment of the wind compass expressions, on which see The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use, and its much more detailed information relevant for navigators, especially on off-shore dangers.

264. See E.5b. ‘Why the Liber’s pelagic statements must have been copied from a cartographic document’.

265. See G.1b. ‘The parenting of the portolan charts’.

266. On which see the separate essay: The Charta Rogeriana: a reappraisal of the making of al-Idrīsī's world map of 1154 and its dissemination (2020).

267. Nevertheless, those compiling world maps in the 14th century certainly appreciated the charts’ superiority and absorbed their outlines for the regions they covered, on which see Marcel Destombes (ed.) Mappemondes A.D. 1200-1500. Catalogue préparé par la Commission des Cartes Anciennes de l'Union Géographique Internationale (Amsterdam: N. Israel, 1964); for a full list of the later mappaemundi see David Woodward, ‘Medieval Mappaemundi’, in J.B. Harley & David Woodward (eds) The History of Cartography, Volume 1 (Chicago University Press, 1987), 366-7.

267a. See C.1. ‘Navigation in the ancient world’.

268. Translation by Elizabeth A. S. Dawes, from Medieval Sourcebook: Anna Comnena: The Alexiad, Book XIII: vii.

269. See K.2a. ‘Earliest mentions’ for the full reference.

270. Pujades, 'The Pisana Chart: really a primitive portolan chart made in the 13th century?' (see note 159).

271. ‘A detailed reassessment of the Carte Pisane: a late and inferior copy, or the lone survivor from the portolan charts' formative period?’.

272. Ibid. For the latest thinking on the Carte Pisane’s dating see the 16 September 2020 note in the ‘Updates’ at the head of the webpage cited in note 271.

273. See E.5b. ‘Why the Liber’s pelagic statements must have been copied from a cartographic document'.

274. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 139-41.

275. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 6.

276. See ’Listing and analysis of portolan chart toponyms along the continuous coastline from Dunkirk to Mogador…’.

277. For a detailed examination of those toponyms and a sketch map locating them, see Kiril Nenov, 'The Black Sea region according to an anonymous Pisan geography', in: Bulgaria Mediaevalis. Studies in honour of Professor Vassil Gjuzelev, Vol.2 (Sofia: Bulgarian Historical Heritage Foundation, 2011), 131-40; for the wider context see Anton Gordieiev [Gordeev], Monography. Place names of the Black Sea and Sea of Azov coasts from portolan charts of XIV-XVII centuries (Kiev: Academia.edu, 2015), 544. That tracks 241 different toponyms through 394 charts and atlases; alternatively access his 2019 update, in Ukrainian, via his Academia page (Gordeev).

278. Nenov, 'The Black Sea region according to an anonymous Pisan geography' (see note 277), 134-5, note 21.

279. I am grateful to Klaus Belke for pointing out that it was on the Asian shore – personal communication 11 September 2020.

280. Nenov, 'The Black Sea region according to an anonymous Pisan geography' (see note 277), 135-6.

281. Ibid. See for the identification of all the tracks, mentioning the few mileage figures that have been provided.

282. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 18-19, refers to instances of missing mileages in other sections – from which he infers that what we have was not the definitive text – but the Black Sea is notable in that respect; Nenov, 'The Black Sea region according to an anonymous Pisan geography' (see note 277), 139, suggested instead that the author ‘was not aware of the distances’, but, if that had been the case, he would surely have omitted the ‘ml.’ prefixes.

283. Nenov, 'The Black Sea region according to an anonymous Pisan geography' (see note 277), 132-3.

284. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 10-11.

285. Ibid., 6.

286. ‘Putting the world in order: mapping in Roman texts’, in R.J.A. Talbert (ed.), Ancient Perspectives: Maps and their Place in Mesopotamia, Egypt, Greece, and Rome (Chicago, 2012), 193-234, at 199-200, fig. 7.3.

287. On which see F. 1b. ‘Measuring distance in terms of time or miles’.

287a. Jacoby, 'An Unpublished Medieval Portolan of the Mediterranean in Minneapolis' (see note 148), 71-2.

288. It is necessary, though to acknowledge a dissenting opinion, though not to concur with it. David Jacoby proposed, on the basis of what he considered to be detailed coverage, a likely date for the Liber in 'the first three decades of the thirteenth century'. Jacoby, 'An Unpublished Medieval Portolan of the Mediterranean in Minneapolis' (see note 148), 72.

289. This point seems not to have been made until it was included in the author’s recently published webpage, The Charta Rogeriana: a reappraisal of the making of al-Idrīsī's world map of 1154 and its dissemination.

290. M. Korte & Catherine G. Constable. 'Continuous geomagnetic field models for the past 7 millennia: 2. CALS7K', Geochemistry, Geophysics, Geosystems, 6, 1 (AGU and the Geochemical Society).

291. Personal communication; and see Joaquim Alves Gaspar, 'Dead reckoning and magnetic declination: unveiling the mystery of portolan charts', e-Perimetron 3:4 (2008), 200-01.

292. See D.3c. ‘Where does the compass fit into the origins debate?’.

293. Pujades, 'The Pisana Chart: really a primitive portolan chart made in the 13th century?' (see note 159).

294. See the comment on that issue in the Carte Pisane essay: Does the toponymy of the Carte Pisane, Cortona and Lucca charts indicate where they might have been made?’.

295. Private communication, 13 November 2018.

296. David Woodward’s authored section in Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 239), 388. It is also relevant here to refer back to a longer quotation from Woodward, in F.3. The 'sub-charts' hypotheses, where he mentioned the idea of a 'self-correcting closed traverse'.

297. On the ways that the triangulated data might have been gathered, see F.2. ’The importance of landward visibility’.

298. Ibid.

299. See F.3. The ‘sub-charts’ hypotheses.

300. British Library, Cotton MS Domitian A. XIII, fol. 115.

301. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 4-6, note 46.

302. The previous meaning was discussed in a paper delivered at the Second International Workshop on the Origin and evolution of portolan charts, Lisbon, 7-8 June 2018 – Abstract, p.21.

303. See E.3b. ‘Why the Liber’s pelagic statements must have been copied from a cartographic document’.

304. See L.3. ‘Literacy or illiteracy’.

305. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34) – see the map at the end. On this see also F.3a. The Adriatic and Aegean.

306. See A.1. Possible cartographic antecedents for the portolan charts. The above remarks were prompted by a suggestion from Wolfgang Koberer. See also a similar thought by the novelist Louise Penney, in A Great Reckoning (2016): “Maps gave them control over their surroundings, for the first time ever. It showed how to get from one place to another. It sounds simple now, but a thousand years ago it would have been an incredible feat of imagination and imagery. All maps are drawn as though looking down. From a bird's point of view. From their god's point of view. Imagine being the first person to think of that. To be able to wrap their minds around a perspective they'd never seen. And then draw it.”

307. Goldie, ‘An Early English Rutter’ (see note 30), 703.

308. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), 20, note 68. “I have already demonstrated that the main geometrical features of portolan charts can be satisfactorily explained by assuming the use of navigational information (pelagic courses and distances between places) in their construction”.

309. Gaspar (Ibid., 2 and note 12) reporting on Scott Loomer’s thesis, wrote that “The results of the analysis pointed to a high degree of correlation between the geometry of the charts and the Mercator projection, from which he concluded that they were based on loxodromic course bearings, rather than distances, probably using some form of triangulation”, continuing that “It must be stressed that Loomer emphatically stated that in his view the medieval cartographers did not consciously adopt any formal map projection”; for Loomer see 'A cartometric analysis of portolan charts: a search for methodology' (see note 239), 107.

310. Ibid., 3, note 17, citing Pedro Nunes, who, in 1537, was the first to describe the geometric basis of the portolan charts – information supplied by Henrique Leitão.

311. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 408. A similar conclusion, in favour of the Mercator Projection, was reached by Tome Marelić, in his doctoral thesis from the University of Zadar, December 2020 – ‘Tocnost prikaza Jadranskog mora na portulanskim kartama’ [The Accuracy of Adriatic Sea Renderings on Portolan Charts] – see the English Abstract. As with Roel Nicolai, that conclusion of a contrived projection carried with it the necessary corollary that the charts had to have been created by competent mathematicians. It would also rule out the mental-map source for the charts, since it would not have been possible to create a cognitive diagram of the interrelationships between the Mediterranean's pelagic termini and then overlay that on a projection that artificially extended distances. For a counter to the intended rather than accidental Mercator Projection claim, see Joaquim Alves Gaspar's review in Maps in History 53 (September 2015): 20-24.

312. Ibid., 350.

313. Pujades, Les cartes portolanes (see note 6), 513b & 516b.

314. Ibid., 516b.

315. Gaspar & Leitão. 'Early Modern Nautical Charts and Maps’ (see note 119), 27-28; for useful references about the role of artisans and scholars in early modern Europe see p.4, note 3.

316. The Hereford mappamundi has Cyprus as a square and Sicily as a triangle, as does the map in an Isidore MS in Munich, see Harvey, Medieval Maps (see note 28), fig. 16 (p.23).

317. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 23.

318. Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 150.

319. It needs to be pointed out that three of the earliest charts, Carte Pisane, Cortona and Avignon, had difficulty in providing direction lines around the junction of the two circular networks. However, had the early sketches been restricted to the Mediterranean alone, without the Atlantic and Black Sea, perhaps only a single circle would have been necessary and that problem would not have arisen.

320. However, Pujades, Les cartes portolanes (see note 6), 418a does note the use of paper, imported perhaps from Alexandria or Constantinople, for use in Italian archives in the second half of the 12th century. The Arabs had obtained the knowledge of paper-making after a battle in 711 and went into production, particularly in Damascus. Some was exported to the West and al-Idrīsī saw that himself in Valencia in 1150. However it seems that European paper “was regarded with disfavor, as not only was it higher in price and more fragile than parchment, which had been used for bookmaking, but it was distrusted on account of its introduction by Jews and Arabs.” Abdul Ahad Hannawi, ‘The Role of the Arabs in the Introduction of Paper into Europe’, MELA Notes, 85 (2012): 14-29, particularly 18-23. (I owe this note to Fateme Savadi). {All but the first sentence added 17 May 2021}.

321. Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 148 & 150.

322. As John Kenneth Hyde pointed out: “From at least the mid 13th century even quite small merchant ships were required to carry not one but two scribes,” for commercial reasons and to record the itinerary, but they would not have been involved in navigation, see Hyde, 'Navigation of the eastern Mediterranean’ (see note 207), 521.

323. For full details see ’Cartographic innovations by the early portolan chartmakers’.

324. However, when that was more appropriate, the chart could be arranged in portrait orientation, such as the detailed focus on the Atlantic coastlines in Andrea Bianco’s chart of 1448 (Biblioteca Ambrosiana, Milan).

325. Patrick Gautier Dalché, 'Maps, travel and exploration in the Middle Ages: some reflections about anachronism', The Historical Review / La Revue Historique, XII (2015): 143-62, at 156.

326. However, see O.1 ‘The portolan charts contrasted with the post-1500 surveys outside the Mediterranean’, for doubts about navigational abilities even then.

327. Pujades, Les cartes portolanes (see note 6), 515a.

328. Debanne, Lo compasso de navegare (see note 160), 86-7 and (partly repeated) 108-9.

329. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 286 (Fig. 8.5) – Malta is in the bottom right corner.

329a. First posited by Aristotle, the wisdom-of-the-crowd theory values more highly the collective opinion of a group over that of any individual, through a process of averaging out the estimates. On this see Wikipedia. This was famously demonstrated at a country fair in Plymouth (England) in 1906, when the middle point of 800 guesses as to the weight of a particular ox proved to be accurate within 1%. This has also been proposed as an explanation for the navigational precision of long-distance flocks of migratory birds, as they follow their shared mental route map passed down in their genes – on which see Scott Weidensaul, A world on the wing: the global odyssey of migratory birds (Picador, 2021), p.83. It is therefore not unreasonable to suggest that a comparable process might have been involved in fixing the position of coastal locations during the proposed rectification period {this note added 17 May 2021}.

330. Pujades, Les cartes portolanes (see note 6), 510b, note 58, citing Lanman, 1987 (see note 22).

331. From ‘De Regimine Principum – on which see K.2a. ‘Earliest mentions’.

332. Other theoretical sub-divisions have been proposed, see F.3. ‘The sub-charts hypotheses’.

333. It needs to be pointed out that Roel Nicolai gives an opposite view: “A point feature will be charted in different locations when different routes to the point are followed and plane charting techniques are applied” – Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 79.

334. An Adriatic restored to its correct size is first seen on the 1330 Angelino DulcetiAngelino Dalorto or Dulceti was a Genoese who worked in Palma, Majorca, leaving us dated charts of 1330 and 1339. His were the first to introduce inland and illustrative details chart, on which see the Carte Pisane essay; for more on the post-Carte Pisane improvements see J.2. 'Charting the Atlantic coasts and the final Mediterranean improvements'.

335. Pujades, Les cartes portolanes (see note 6), 461.

335a. For more details on this see, ’Stages in the construction of a chart’.

336. The marginal portraits were evidently provided by a specialist illuminator.

337. See K.2c. ‘How were the dangers recorded and how did those get onto the charts’; and for a comment about fishermen as informants see K.2d. ‘Fishermen'. [A separate essay is contemplated around the vital issue of the method(s) used to replicate the portolan charts].

338. See H.2. ‘Dating the portolan chart’s appearance: why the Liber’s account of the Black Sea and the Charta Rogeriana are important’.

339. See supplementary notes about the ‘Black Sea’.

340. See H.2a. 'The Liber’s Black Sea toponyms'.

341. Which prompts the observation of how bodies of water are still side-lined in world atlases. In my Times Atlas four sheets are required to see the Black Sea, with the south-eastern section at a far smaller scale.

342. That is in the unlikely scenario that mariners drawing out the sea’s outlines in the 13th century were aware of the Geographia’s text, let alone the maps.

342a. For the early unsigned and undated charts see N.1b. 'Not a single lineage'.

343. Debanne, Lo compasso de navegare (see note 160), 120-5.

344. Ibid., 27.

345. Whereas the Liber’s lack of available information c.1210 is understandable, it is surprising that the compilers of earlier iterations of Lo compasso did not think it necessary to incorporate the Black Sea.

346. See 'An intentionally truncated Black Sea?' There is an instructive contrast here with the first production of Pietro Vesconte, whose chart of 1311 excludes everything west of Sardinia. Clearly different priorities were involved.

347. See the Carte Pisane essay section on the ‘Black Sea’.

348. It can be noted, for numerical comparison, that about 130 toponyms can be seen on the Ptolemaic maps (in the printed atlas of 1478) and 45 on al-Idrīsī’s world map. Vesconte started with 156 Black Sea names, to which a further 52 would be added in the 14th century. On the toponymy statistics, see the tables attached to ‘The Introduction and Abandonment of Toponyms on Portolan Charts 1300 to 1600’. For the definitive analysis of Black Sea names see Gordieiev, Monography. Place names of the Black Sea and Sea of Azov (see note 277).

349. On which see a summary note in the essay on Grazioso Benincasa.

350. See G.1c. ‘The coastal itineraries'.

351. Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 67.

352. For a note on the problem of determining directions and measuring distances along the coast, see G.1d. ‘Settling the priority question’.

353. Lanman, On the origin of portolan charts (see note 22).

354. See Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 275 et seq. Lanman subscribed to the thesis that a written portolano preceded the chart and indeed could have itself provided a plausible chart. See ‘Alternative origin hypotheses’.

355. Jacques Mille, The French Mediterranean coasts on portolan charts (self-published, 2016), 6-7.

356. Personal communication, 15 January 2019, from Zoltán Biedermann, who has studied the significance of different coastline patterns.

357. Writing about a chart by Bartolomeu Velho of c.1560, Zoltán Biedermann noted that “the surveyed littorals appeared in a clear and precise visual idiom known as the ‘portolan style’. Unexplored shores, in contrast, were rendered through slightly undulating lines” – ‘Drawing Lines to Tame the Unknown: A Typology of Littorals in Early Modern Maps’.

358. For improvements observed in the coastal outlines between the time of the Carte Pisane and Vesconte in 1311 see the Carte Pisane essay (sections E.5c-E.5e, covering Asia Minor, the Gulf of Sirte and the larger islands.

358a. Michael Barritt suggests that this is the Nahr al-Kabir al-Shamali, now much reduced by upstream dams and emerging just west of Bassel Al-Assad International Airport.

359. As an exception, the Vescontes included loose depictions of the inland Danube. On the significance of ports, see Catia Antunes and Louis Sicking, ‘Ports on the Border of the State, 1200 1800: An Introduction’, International Journal of Maritime History 19: 2 (2007): 273-86.

360. See K.2. ‘Navigational Dangers’.

361. An alternative explanation would be that the truncated lines defining the river mouth represented a saving of time both for drawing the river itself and when subsequently locating the place-names.

362. ‘The vast majority of islands are visible from the peaks and elevated shorelines of adjacent mainland areas or form links, or “stepping stones,” in a chain of islands tied to the mainland by their mutual, island-to-island visibility …’ – Davis, 'Commercial Navigation in the Greek and Roman World' (see note 86), 22.

363. For specific details see E.5e. ‘Larger Islands’.

364. Tony Campbell, ’Why the artificial shapes for the smaller islands on the portolan charts (1330-1600) help to clarify their navigational use’, Cartes et géomatique, 216 (June 2013): 47-65 (paper delivered at the international conference, 'D'une technique à une culture: les cartes marines du XIIIe au XVIIIe siècle', Paris 3 December 2012. Note that there were also post-1500 repetitions, on which see ‘O.1. The portolan charts contrasted with the post-1500 surveys outside the Mediterranean’.

365. On the ambiguity of the meaning of some toponyms see ‘The meaning of names’.

366. Gaspar, 'The Liber de existencia riveriarum (c.1200)’ (see note 12), Figs 4 & 7.

367. See K.1a. ‘What was the source for the coastal outlines?’.

368. See Cristoforo Buondelmonti, Description of the Aegean and Other Islands . Edited and Translated by Evelyn Edson (Italica Press, 2017); also George Tolias, ‘The birth of the genre: Florence, fifteenth century’, in David Woodward (ed), The History of Cartography. Volume Three. Cartography in the European Renaissance, Part 1, 265-7, where mention is made of the possible influence of the portolan charts (267).

369. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 421 – though the enlarged scale could have followed automatically from filling a sheet of predetermined size with a smaller geographical area.

370. See ‘Contents of the Charta Rogeriana’.

371. See K.1d. ‘Islands’.

372. The Mediterranean, A Memoir Physical Historical and Nautical (London, J. W. Parker and Son, 1854) – a reference I owe to Michael Barritt. The only other contribution of which I am aware was made by James E. Kelley, who focused on the vigias, fictitious or temporary hazards, see James E. Kelley, Jr, 'Curious vigias in portolan charts', Cartographica 36,1 (Spring 1999, i.e. April 2000): 41-9; and also his article with the same title published in: On Old Nautical Charts and Sailing Directions: Technical Essays (Melrose Park, PA: Sometime Publishers, 1999), 253-9 (in a section labelled: ‘1st draft 1986, Revised 1997’).

373. Tony Campbell & Captain Michael Barritt RN. ‘The Representation of Navigational Hazards: the Development of Toponymy and Symbology on Portolan Charts from the 13th Century onwards’, The Journal of the Hakluyt Society, December 2020.

374. See ’Development of the signs for navigational dangers’ [Table 7].

375. “The symbols on a portolan chart indicating dangers, such as the variable depths in the approaches to the River Ebro, were as effective as the warning notes on modern charts.” (Michael Barritt, Lisbon 8 June 2018).

376. Emmanuelle Vagnon, ‘Cartographie et représentations occidentales de l'Orient méditerranéen, du milieu du XIIIe à la fin du XVe siècle’, Terrarum Orbis, 11 (Turnhout: Brepols, 2013): 140-2 (originally included in her doctoral dissertation of 2007). I owe this reference and the English translation to Peter Barber.

377. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 175 [line 2261].

378. Ibid., lines 2255-67.

379. See further, M.1b. ‘The advantages to a navigator of a chart over a portolano.

380. See ’Patterns’ and scroll down to ‘Small hydrographical details’.

381. Kevin Sheehan, 'The Functions of Portolan Maps: an evaluation of the utility of manuscript nautical cartography from the thirteenth through sixteenth centuries', PhD dissertation, Durham University, July 2014.

382. Ibid., 108.

383. Ibid., 100.

384. Jacques Mille, The French Mediterranean coasts on portolan charts (self-published, 2016).

385. For the geographical spread of the dangers first recorded on Lo compasso, see ’Navigation Dangers Summary Table’ – an Excel spreadsheet (sort on column T).

386. Ibid. The spreadsheet lists the named navigational hazards with their first recorded appearance in a text or on a chart.

387. Ibid. Sort on columns K & L.

388. Debanne, Lo compasso de navegare (see note 160) supplies a valuable glossary of the technical terminology of the medieval sailor as preserved by the creator of Lo compasso, which includes an extended thesaurus denoting specific dangers, e.g.:

  • rocks or reefs (clappa / klappa, escoio, farillione, planca, roccia, roches, rupe, scogli / scolli, scolliera)
  • sandy shoals (arena / arenile, grado, lena, piage / plaia, placca, sabbia, spiaggia)
  • shoals (asperile, estagno, secca / seche)

389. To isolate those instances, sort the Excel spreadsheet (see note 385), on columns S & T.

390. See K.3c. ‘Toponymic referents’.

391. See the author’s Excel spreadsheet: ’Listing and analysis of portolan chart toponyms along the continuous coastline from Dunkirk to Mogador…’; and also Kevin E. Sheehan. 'The Appearance of Lighthouses on Portolan Charts: 1300-1600 AD', in: Judith Mills & Marjolein Stern (eds), North and South, East and West: Movements in the Medieval World: Proceedings of the 2nd Postgraduate Conference of the Institute for Medieval Research, University of Nottingham, 30-31 May 2009; Jesús Ángel Sánchez García. 'Unveiling a Ghost / Desvelando un fantasma. Sobre un mapamundi árabe, la Torre de Hércules y las representaciones de faros en la cartografía medieval', Memoria y Civilización, 20 / 2017. Revista del Departamento de Historia, Historia del arte y geografía, Facultad de Filosofía y Letras, Universidad de Navarra (2017): 259-308; and Ken Trethewey. Ancient Lighthouses [See his Academia page, for a multi-part series of papers (2018), including 'Part 1: The Literature' and 'Part 8: An Overview']. For signalling towers that conveyed information to mariners via a kind of semaphore, such as the Torre de Farell on Monjuic (Barcelona), which, though documented from the 11th century, seems first to have been depicted on a chart by Gabriel Valseca in 1449, see Sandra Sáenz-López Pérez, 'Las voces silenciosas de las torres de señales: un sistema de comunicación mediterráneo ahora perdido’, Anales de historia del arte, nº extra (2009): 323-37.

392. Personal communication from Michael Barritt, November 2019; likewise Giacomo Marieni, when surveying the Adriatic in 1818-19, referred to experienced fishermen who “were without doubt the best acquainted with the seabed” – quoted in Imago Mundi 69:1 (2017): 104.

393. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 427-8. The Statement to the Reader is transcribed (but not translated) in Pujades, Les cartes portolanes (see note 6), 461.

394. Amy Remensnyder, ’Mary, Star of the Multi-Confessional Mediterranean: Ships, Shrines and Sailors’, in: Nikolas Jaspert, Christian A. Neumann, & Marco di Branco (eds), Ein Meer und seine Heiligen: Hagiographie im mittelalterlichen Mediterraneum (Paderborn: Wilhelm Fink, 2018), 301-2); on mariners' beliefs and observances, see Peregrine Horden and Nicholas Purcell, The Corrupting Sea: A Study of Mediterranean History (Oxford: Blackwell Publishers, 2000); Timmy Gambin, 'Maritime activity and the Divine – an overview of religious expression by Mediterranean seafarers, fishermen and travellers’, in: Dionisius A. Agius, et al. (eds), ‘Ships, Saints and Sealore: Cultural Heritage and Ethnography of the Mediterranean and the Red Sea’ (Archaeopress Oxford, 2014): 3-12; and Goldie, ‘An Early English Rutter’ (see note 30).

395. Aaron J. Brody, ‘The Specialized Religions of Ancient Mediterranean Seafarers’, Religion Compass 2 (2008).

396. Westerdahl, ‘Odysseus and Sindbad as metaphors’ (see note 17), 50.

397. See ’Some areas for possible future research into Portolan Chart history’ – under ‘sante parole’.

398. Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 125-53.

399. See L.2b. ‘The London Underground Map.

400. O’Connor, Wayfinding (see note 57), 118. For detailed analyses and explanatory essays about portolan chart toponymy in general, see the Toponymy section on the Contents page on ‘Map History’ and, from the Carte Pisane essay ’What toponymic sources might have been used by the early chartmakers’.

401. See N.2a. ‘The possible contribution of merchants to the charts’ origin and development’.

402. See M.1d. 'Usage by non-mariners’.

403. ’Listing and analysis of portolan chart toponyms along the continuous coastline from Dunkirk to Mogador…’.

404. See ’Names on the two early portolani related to those on the four charts’.

405. For statistical detail on these comparisons see the Carte Pisane essay – and particularly the tables listed at the end of the Contents page.

406. The ‘heterogeneity’ of the two early portolani was noted by Pujades, Les cartes portolanes (see note 6), 512b.

407. A digital tool for comparing text, 'veccompare', which could presumably be applied to this toponymy question, has been announced and demonstrated: Heather Wacha & Jacob Levernier, 'Cartography and Code: Incorporating Automation in the Exploration of Medieval Mappaemundi', Digital Medievalist, 12(1) (2019).

408. Portolani and printed charts’ on the 'Toponymy Innovations' page.

409. For a detailed analysis of the North Sea on the recently discovered Avignon chart, and suggested matching of its toponymy to modern names, see the publications of Jacques Mille, via the Portolan Chart ’Bibliography’.

410. But not seas, straits and other maritime divisions, which the charts largely omit.

411. For more on referents see ‘The meaning of names’.

412. See ‘Innovative Red name totals by individuals to 1600’ (Table 2).

413. For the instances see ‘Summary Table of Red Names: their appearance, frequency and disappearance’, sorting on column 12.

414. I was alerted to this question by Ljiljana Ortolja-Baird. For an examination of the incidence of red names on the portolan charts from the outset up to 1700 see ‘Red Names on the Portolan Charts (1311-1677): a detailed investigation’.

415. See K.3a. ‘The Carte Pisane’s toponymy compared to that of the portolani'.

416. See Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 422.

417. For full details, see note 6.

418. ’Listing and analysis of portolan chart toponyms along the continuous coastline from Dunkirk to Mogador…’.

419. For the statistical details, see the Toponymy Menu and scroll to the tables at the end.

420. See the introduction to the Toponymy Innovations (see paragraph 8).

421. See the essay, ‘Innovative Portolan Chart Names’ and in particular ‘Historical time-lag’ and ‘Dissemination time-lag’.

422. 'Toponymy Innovations’ [Table 1].

423. Andrea Bianco, Francesco Cesanis, Nicolo Fiorino, Nicolo Nicolai, Cristoforo and Zuan Soligo, Albertin di Virga, Giacomo Ziroldi, and the Anconitan Grazioso Benincasa – see Piero Falchetta, 'Marinai, mercanti, cartografi, pittori. Ricerche sulla cartografia nautica a Venezia (sec. XIV-XV)', Ateneo Veneto 182 (1995): 7-109. For their sparse toponymic introductions see ‘Toponymy Innovations’ [Table 3].

424. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 427-8; Pujades, Les cartes portolanes (see note 6), 461, includes the full untranslated text.

425. The broadly unchanging sea atlases produced by Mount & Page and their successors for the use of British sailors throughout the 18th century provides an instructive parallel. In each case, a fixed model – whether the portolan chartmaker’s pattern or the publisher’s engraved copperplate – encouraged conservatism.

426. On this topic see further ‘The mechanisms for the staged introduction and repetition of new names’, under ’Incorporation of toponyms’.

427. Cited in Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 372.

428. Ibid., 398-401; and see also the Update notes to that.

429. For details of these developments see ‘Innovative Portolan Chart Names’.

430. On which see N.3a. ‘Survival’.

431. See L.3c. ‘What textual information was included on the charts and what omitted?’; and for the lack of any input from landsmen see M.1d. ‘Usage by non-mariners’.

432. Joaquim Alves Gaspar, private communication 4 March 2020.

433. See A2. ‘Why is there a widespread assumption in favour of a textual origin for the portolan chart’; and also I.3c. ‘Missing link’.

434. See M.1a. ‘Planning a voyage’ and K.2d. ’Fishermen’.

435. “After the ship-boy had served for some time in his apprenticeship, and had become an expert in life on board, in manoeuvres and navigation, he was to learn the use of the portolan chart and become conversant with calculating the ship route” – Piero Falchetta, 'The use of portolan charts in European navigation during the Middle Ages', in: Ingrid Baumgärtner & Hartmut Kugler (eds) Europa im Weltbild des Mittelalters: kartographische Konzepte. Orbis mediaevalis: Vorstellungswelten des Mitttelalters. Bd.10 [Proceedings of the conference held in Nuremberg, 15-17 June, 2006] (Berlin: Akademie Verlag, 2008) 275.

436. Pujades, Les cartes portolanes (see note 6), 23 (illustrating a sample); on the mental wind compass see The mental wind compass of the medieval Mediterranean: the rediscovery of its structure and interpretations of its use (2020).

437. Ibid., 514b.

438. On the issue of whether measurements in miles were used or simply hand spans see F.1b. ‘Measuring distance in terms of time or miles’, and on scale see F.1c. ‘Scale(s) of the portolan charts’.

439. On the dangers symbols see K2. ‘Navigational dangers’.

440. Given that the stippling for shoals must have taken the copyist a considerable amount of time why did they not instead outline the extent of that feature and just write secca (shoal), perhaps with its name? No significant information would have been lost. Why those details were to continue unaltered through the centuries reflects the tight discipline of the chartmaker’s atelier, but that doesn’t explain why those features were treated so elaborately from the outset.

441. Carte Pisane Hydrography Tables [Table 7].

442. See K.1b. ‘How were the coasts demarcated?'.

443. See K.1c. ‘Rivers’.

444. See K.3c. ‘Toponymic referents’.

445. See 'Cartographic innovations by the early portolan chartmakers' (note 33).

446. See C.2c. 'Mediterranean navigation: Sea signs'.

447. See the note at the end of K.2c. ‘How were the dangers recorded and how did those get onto the charts?’.

448. See B.2. ‘The brain and spatial memory’.

449. O’Connor, Wayfinding (see note 57), 68 and 157.

450. From ‘Nea Mathisi’, Chapter 1.

451. ‘How reading affects us’, a 10-minute YouTube presentation, 13 June 2010. (I owe this reference to Robbie Campbell).

452. See B.3b. ‘Western examples of mental navigation maps’.

453. ’The secret green shelters that feed London’s cabbies’ – Ella Buchan, BBC, 1 May 2018.

454. Rebecca Campbell, ’Spatial Orientation and the Brain: The Effects of Map Reading and Navigation’, GIS Lounge, 8 March, 2013.

455. There is however a precedent for noting this parallel. The commentators on the 11th-century Islamic Book of CuriositiesAn Arabic manuscript of the 11th century including maps and descriptions of the Mediterranean, but not related to the portolan chart – see Section A.3a, and Rapoport & Savage-Smith, 2018 compared the 10th-century Balkhi School maps to the London Underground Map. The textual narrative of the Balkhi land routes was “transformed and abstracted to a series of straight lines, with only minimal orientation and no indication of scale“. See Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 142.

456. Catherine Delano-Smith: ‘For whom the map speaks: Recognising the reader’, in Paula van Gestel-van het Schip & Peter van der Krogt (eds), Mappae Antiquae. Liber Amicorum Günter Schilder (‘t Goy-Houten: HES & De Graaf, 2007), 634.

457. An important qualifying comment needs to be made. As the Underground historian Douglas Rose has discovered, a few of the novel features on Beck’s map had been used four years earlier by George Dow. To pursue this see a bibliographical note by Kenneth Field on the Map Room blog, 1 May 2018. Whether or not Beck had seen Dow’s work, it is generally considered that the credit for the map’s overall concept and its detailed structure remains with Beck.

458. See the equivalent list of unstated and supplementary information required for the full utilisation of the portolan chart: L.1a. 'What needed to be explained orally for the charts’ effective use’.

459. See N.2b. ‘How important was trade in the charts’ origin?’.

460. See D.3c. ‘Where does the magnetic compass fit into the origins debate?’.

461. It is true that during the period Beck was working on the design in the 1920s the network was undergoing significant expansion. But that would not have provided the prompting for a new plan because the additions were extensions into the suburbs and the density of the crowded central area, where the cartographic problems lay, was not affected. See 'Timeline of the London Underground’, and also Darien Graham-Smith, 'The History of the Tube Map', Londonist, 6 April 2018.

462. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 183-203.

463. "For the types of ships built in private shipyards he describes a system based on a proportional approach; for the galleys built in the state-run Arsenal his approach reflects the recording of actual measurements on paper:" ’Ships and Shipbuilding’ – Dibner Institute for the History of Science and Technology, 2005.

464. Wikipedia, citing: Renaud Beffeyte, ‘The Oral Tradition and Villard de Honnecourt’ (2004).

465. T. Sutton, ‘A note on medieval local maps and their readers’, Imago Mundi 71:2 (2019), 197. There is an interesting parallel in the baptism of sailors, for which the earliest recorded reference is from the later 16th century. It was concluded that the reason for this was because sailors kept it to themselves, see Westerdahl, ‘Odysseus and Sindbad as metaphors’ (see note 17), 42 (citing Henningsen).

466. Tony Campbell, ‘The woodcut map considered as a physical object: a new look at Erhard Etzlaub's Rom Weg map of c.1500’, Imago Mundi 30 (1978): 83.

467. Waters, The art of navigation in England in Elizabethan and early Stuart times (see note 91), 31-2 and the associated illustrations.

468. For arguments about whether the portolan charts themselves had a textual origin, see A.2. ‘Why is there a widespread assumption in favour of a textual origin for the portolan chart'?, and for the relationship between literacy and memory, see C.3. ‘The mental map in the Mediterranean context’.

469. Campbell & Barritt, 'The representation of navigational hazards’ (see note 373).

470. Ramon J.Pujades i Bataller, La carta de Gabriel de Vallseca de 1439 (Barcelona: Lumenartis, 2009), see the loose folding table.

471. Pujades, Les cartes portolanes (see note 6), 459-60.

472. George Tolias, The Greek portolan charts, 15th-17th centuries: a contribution to the Mediterranean cartography of the modern period (Athens: Olkos, 1999), 42.

473. Sheehan, ‘The functions of portolan maps’ (see note 381), 100 & 108, who concluded that an undecorated chart would have taken about three weeks to produce.

474. See ’Toponymy on charts produced outside the Mediterranean’.

475. Tony Campbell, ‘Why the artificial shapes for the smaller islands on the portolan charts (1330-1600) help to clarify their navigational use’.

476. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 416a & 419b.

477. Wikipedia.

478. I.3. 'What might such a pelagic diagram have looked like?'.

479. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 441-3, and the 'Portolan charts from the late thirteenth century to 1500. Additions, Corrections, Updates' to those pages, under ‘Shipboard use’ and the section that follows, ‘Navigational practice’.

479a. Ibid.

480. See H.1a. The confirmed 'terminus ante quem'.

481. Cunliffe, On the ocean: the Mediterranean and the Atlantic from prehistory to AD 1500 (see note 83), 69.

482. See E.5b. ‘Why the Liber’s pelagic statements must have been copied from a cartographic document’.

483. See Rapoport & Savage-Smith, Lost maps of the Caliphs (see note 37), 133, who explain that the winds facilitated a journey in that direction but, for going northwards, the voyage had to be along the Levant coast.

484. See C.1.‘Navigation in the Ancient World’.

485. Pujades, Les cartes portolanes (see note 6), 465a.

486. See K2.‘Navigational Dangers’.

487. See, for comparative mentions of named dangers on the two works, ‘Navigation Dangers Summary Table’. Jacques Mille kindly provided confirmation of details along the coast of Provence not found on the charts until the Beccari familyFrancesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library) (personal communication, May 2020).

488. Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), 19, 29-31.

489. Other smaller gaps have also been noted, see Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 383.

490. On which see G.1d. ‘Settling the priority question’.

491. On which see L.1a. 2. ‘Information not provided by the charts but necessary for navigation'.

492. Hyde, 'Navigation of the eastern Mediterranean’ (see note 207), 532.

493. Cited in Gautier Dalché, 'Maps, travel and exploration in the Middle Ages’ (see note 325), 154.

494. The Riverside Chaucer, lines 401-9.

495. The occasional references to the ruins of an old town alongside the modern replacement are unlikely to indicate an antiquarian concern on the part of chartmakers, rather that those could help in visually locating the ship’s position. Search the Excel spreadsheet: ’Listing and analysis of portolan chart toponyms along the continuous coastline from Dunkirk to Mogador…’ for ‘vechia’ or ‘vecchia’ to retrieve a few examples.

496. Pujades, Les cartes portolanes (see note 6), 521b.

497. Sheehan, ‘The functions of portolan maps’ (see note 381), 108, concluded that a functional chart of the full usual extent would have taken around three weeks; the same period was mentioned by the 17th-century English chartmaker, Nicholas Comberford, for his illustrated productions, see Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 436. note 465.

498. For Jacques Mille’s studies on the Avignon chart see the Portolan Chart Bibliography.

499. Philipp Billion, 'A newly discovered fragment from the Lucca Archives, Italy', Imago Mundi 63: 1 (2011): 9-11, Plates 1 & 2.

500. Pujades, Les cartes portolanes (see note 6), C6 on the accompanying DVD; see also a note on the Carignano map; and a scan is provided by the Florence Archives.

501. See a note on the Riccardiana chart.

502. On which see, What is meant by an 'atelier'?.

503. Not surprisingly, given their far wider relevance, the Bible and books of hours circulated in very large numbers from the 13th century. Those were mass produced in lay ateliers, as decorated texts for sale. In the case of the Paris Bible they were arranged in standard chapters for ease of reference, with attention to the practical aspect, and in small format for portability. All of that has echoes in the practicality of the portolan charts. I am grateful to Richard Gameson for this information.

504. See H.1a. The confirmed 'terminus ante quem'.

505. e.g. by the Datini firm, see Pujades, Les cartes portolanes (see note 6), 459-60.

506. The totals, with some of the dating being necessarily approximate, since almost half lack a stated date, are: 683 (16th century), 922 (17th), 255 (18th). 'Pflederer Census of Portolan Charts and Atlases' (edition September 2020 – available at no charge from the author, Richard Pflederer: rlpfled@prodigy.net).

507. On the issue of the commercial dissemination of the charts, follow up the ‘Chart trade’ references in 'Portolan charts from the late thirteenth century to 1500. Additions, Corrections, Updates'.

508. See ’The Vallseca contract of 1433’.

509. See N.3a. ‘Survival’.

510. See ‘Traces of master/apprentice relationships’.

511. See N.1b.’Not a single lineage’.

512. Francesco Beccari Francesco and his son Battista were active in or around Genoa in the first half of the 15th century. Francesco’s 1403 chart is notably innovative (New Haven, Yale University, Beinecke Library) provides a neat proof that he had not served an apprenticeship. For two of the toponyms – aygue morte (S. France) and damiata (Egypt) – some chartmakers, from about 1330 onwards, separated off the first one or two letters and placed those on a nearby island. [For the details, see ‘The features chosen to illustrate the developing portrayal of islands and estuaries on portolan charts up to 1469’ (see Nos 23 & 51).] Not realising that, Beccari superfluously repeated the initial ‘a’ for the first instance and swung round the ‘d’ in the second, proving that he did not understand the purpose behind those two idiosyncrasies [Powerpoint, Slide 28].

513. H.3. ‘Where might the portolan chart have been initially developed?’.

514. For an example of that see ‘Andrea Bianco's "London" chart of 1448’.

515. See for example, Ingrid Houssaye Michienzi & Emmanuelle Vagnon, ‘Commissioning and Use of Charts Made in Majorca c.1400: New Evidence from a Tuscan Merchant's Archive', Imago Mundi 71:1 (2019): 22-33 [available free here]; and R. A. Skelton, ‘A contract for world maps at Barcelona, 1399-1400’, Imago Mundi 22 (1968): 107-13, especially 107-9.

516. For example, in discussion at the ‘Second International Workshop on the Origin and Evolution of Portolan Charts’, in Lisbon, 7-8 June 2018.

517. Campbell, ‘Portolan Charts from the Late Thirteenth Century to 1500’ (see note 5), 398-401, and the update notes to that chapter: ‘Stylistic development: Flags’.

518. Interestingly, and perhaps uniquely, the Liber includes the names of several places along the Rhône, the only large river accessible to sailors from west Italian ports. See Gautier Dalché, Carte marine et portulan au XIIe siècle (see note 34), lines 1872-5.

519. See ’The Vallseca contract of 1433’.

520. Some merchants were sailors as well, leading Ramon Pujades to refer to “merchant-mariners and mariner-merchants”: Pujades, Les cartes portolanes (see note 6 ), 518a.

521. On the later use by trading houses, for example Datini, see Ibid., 459-60; and Ingrid Houssaye Michienzi and Emmanuelle Vagnon, ‘Commissioning and Use of Charts Made in Majorca c.1400: New Evidence from a Tuscan Merchant’s Archive’, Imago Mundi 71:1 (2019), 22-33 [available free here], where the Datini-commissioned charts were evidently used both to prepare for a business trip and embody the memory of it afterwards.

522. For a visual picture of those patterns see the diagram included in Pujades, Les cartes portolanes (see note 6), 34-7; see also Martin Jan Mansson’s ‘Medieval trade route networks’, though the routes shown are mostly over land. Ramon Pujades, for example, has discussed the maritime trade background in detail see Pujades, Les cartes portolanes (see note 6), 414-22; see also the 'Portolan charts from the late thirteenth century to 1500. Additions, Corrections, Updates'. One measure of trade concerns wrecks and, since wood does not normally survive, the best evidence available is amphorae and, because of their regional styles, anchors, on which see Peta Knott, ‘Weighing Down the Trade Routes’ (Honours Thesis, University of Sydney, 2003), “describing how the distribution of anchors geographically and chronologically will be examined to show trade route patterns”. As she points out “anchors show trade – the long-distance exchange of goods, not available locally, by sea between different settlements – in progress” (11 & 13).

523. For a rebuttal of the suggestion that the opening up of the Black Sea to the Venetians in 1204 might have provided the trigger for the chart’s creation see H.2d. ‘Establishing a terminus ante quem for the portolan chart'.

524. See D.3c. ‘Where does the magnetic compass fit into the origins debate?’.

525. See under N.1e. ‘Customisation’.

526. I owe the suggestion in the final sentence to Corradino Astengo and Joaquim Alves Gaspar.

527. See M.1d. ‘Usage by non-mariners’ for enhancements that merchants might have requested, but did not.

528. On which see ’A note on the Cornaro Atlas’.

529. See the Excel spreadsheet, ‘A complete chronological listing of portolan charts assigned to the period pre-1501’ [sorting on Column C].

530. As Ramon Pujades pointed out, "Inventories abound with references to old, torn charts, and narrative and poetic sources with allusions to their use on ships" – Pujades, Les cartes portolanes (see note 6), 456a.

531. Maev Kennedy, ‘What lies beneath’, The Guardian newspaper, 28 August 2009.

532. Burney MS 111 [select f. 102v from the list of folios down the right side].

533. Campbell, ‘Why the artificial shapes for the smaller islands on the portolan charts (1330-1600) help to clarify their navigational use’ (see note 475).

534. “The geodetic basis of the charts, expressed in their accuracy and their map projection, is far beyond the capabilities of the European Middle Ages. Far from being primitive charts that are mildly anomalous in the Middle Ages, the charts are sophisticated cartographic products that can neither be explained in any way from medieval European, nor from Arabic-Islamic available geodetic-cartographic capabilities” – Nicolai, A critical review of the hypothesis of a medieval origin for portolan charts (see note 10), 410. On the early refinements to the outlines seen on the Carte Pisane see J.2. ‘Charting the Atlantic coasts and the final Mediterranean improvements’.

535. Monique de La Roncière & Michel Mollat du Jourdin (trans. L. le R. Dethan), Sea charts of the early explorers: 13th to 17th century (London: Thames & Hudson, 1984), 8.

536. “It answers questions that we not only do not ask but do not understand, and it falls short in answering the questions we ask about it” – review by Thomas O’Loughlin in the IMCoS Journal, 161 (June 2020): 53-4.

537. As itemised in Cartographic innovations by the early portolan chartmakers.

538. It is presumptuous to compare the search for the portolan charts’ origin with the greatest of all maritime mysteries, the ‘Eel Question’, because the untangling of the eels’ four forms and its reproduction methods has intrigued marine biologists since the time of Aristotle. But the attempts to explain the charts’ inception do mirror aspects of that zoological puzzle. In that case, a succession of discounted theories have been replaced in modern times with careful observation that was sufficient to answer most of the questions, yet leaving continuing speculation as to precisely where and how the eel reproduces. At that point empirical science had to give way to deduction, which is effectively all that a portolan-chart historian has available, once mathematical scrutiny has made its contribution. For a readable account of the eels’ history see Patrik Svensson, The Gospel of the Eels (Picador, 2020).

539. For details of these see ’Census of pre-sixteenth-century portolan charts: Additional ('E') entries’.

 


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