Overview

Portolan charts have long been admired for their surprising overall spatial accuracy, presenting, on what is generally considered to be the oldest survivor, the Carte Pisane, coastal outlines for the Mediterranean and Black Sea that are fully recognisable today.

This book-length study does not participate directly in the debate about the origin of the portolan charts, and when that was supposed to have occurred. However, by identifying further, fundamental innovations in the charts during the early decades of the 14th century - particularly a massive injection of new toponymy - it does comment, if obliquely, on the likely appearance of their 13th-century predecessors, for which we have no tangible evidence. [On this and a wide range of other points relating to the charts' early history see the extended essay on the dating of the Carte Pisane (March 2015) and another long essay, on the Origins of the charts (January 2021).]

Nor is this a general history of those charts through the centuries, a mere summary of what was previously written. Instead, these pages display the results of several new, in-depth studies. Based on the old adage that 'the devil is in the detail', the focus has been on smaller features, those not previously considered of any significance. Panning for gold along some of the subject's lesser tributaries has proved surprisingly rewarding. Close observation of such previously overlooked aspects as the colour and shapes of the smaller islands, and a few previously unremarked stylistic conventions, have revealed new insights into the charts' purpose(s) and helped us understand why such an apparently static functional tool should have remained relevant for so long.

Similarly, the first general survey to be attempted of portolan chart toponymy has thrown into relief the erratic manner in which names first found their way onto a chart and then migrated to others. These new evidence-based conclusions, to which a new study of red names has contributed, are a corrective to some existing assumptions and certainties.

Mnemonic island shapes
While the same careful delineation of the coastline was also applied to the larger Mediterranean islands, it does not seem to have been appreciated that the handling of the smaller islands was noticeably different. 14th-century charts display strange geometric shapes for islands in the largely unknown Atlantic, which, if they existed at all, had certainly never been charted. That seems fully understandable to a modern viewer. But the application of that same approach to islands in the Adriatic, and even more so the Aegean, demands a different explanation.

Why were certain distinct, but 'man-made' and wholly implausible shapes given to the islands and islets of the Aegean? Why were those idiosyncratic forms copied by one practitioner from another, and, broadly, persisted with by chartmakers for well over three centuries? Why was this treatment given to islands that were well known to the ships of the three early chart-making powers: Catalonia, Genoa and Venice? Indeed, in some cases they even had a settled presence on the island in question.

Larger islands, such as Majorca and Cyprus, were outlined with overall fidelity because sailors needed to know the locations of headlands or bays and the names of harbours, just as they did along the equivalent stretches of the continental coast. However, on the smaller islands there was room for neither place-names, nor, at that relatively small scale, any coastal detail. Instead, it is proposed here that the bizarre shapes given to the smaller islands were chosen intentionally, as a visual mnemonic device. Their true, and sometimes complex outlines were consciously distorted into widely varying shapes so as to provide an easily-memorised way of distinguishing one from another.

Chart function
There is no documentary evidence to support that interpretation (it would be surprising if there were) nor has any direct pre-1311 antecedent yet been found for what must seem to a modern viewer like a planned subversion of the portolan charts' overall geometric accuracy. The explanation proposed in these pages requires a rethinking of the charts' purpose. We now know for certain that sailors routinely took charts to sea with them but arguments continue about their precise onboard function. I suggest that we need to distinguish three quite separate uses of a portolan chart at sea: first, for assisting navigation when out of sight of land; second, to confirm the ship's position along a coastline, with reference to observed headlands or islands; and, third, when picking a way through an archipelago (such as those in the Aegean).

The charts' overall fidelity in terms of distance and direction (once the user had made adjustment for the deviation of his compass) provided an essential tool when navigating in the open sea. The bearing to the destination would have been noted beforehand and an attempt then made to keep track of the actual, indirect course followed. Once land was sighted, the headland could be visually identified, and the sequence of named geographical features and settlements indicated on the chart used as a guide when proceeding along the coast. But the charts made no pretence at any realistic infilling of the coastal configuration between the (often exaggerated) headlands.

The non-realistic treatment of the smaller islands mirrors that for the separate coastal stretches. What mattered for this position-fixing stage of inshore navigation was to know the distance from one place or headland to another and their direction (which would be obvious when they were intervisible). For a small island, the navigator needed to know the approximate size and position but the shape was of no significance to him as he would be sailing past, not round it. So what we find with, say, the lesser Aegean islands is that they are broadly true as to position and size, despite their artificial shapes. And even the smallest islet is carefully named, providing a comprehensive toponymic catalogue of the archipelago, as a counterpart to the visual catalogue of their signature shapes.

That the mnemonic form was of more practical use than the sometimes clumsy attempt at realism can be seen by the longevity of the most striking construct of all, the series of 'lollipop' projections placed on three sides of a roughly square Limnos in 1330, and still largely present on charts at the end of the 17th century. Even more surprisingly, such excrescences were added - by the Catalan chartmakers - to their home island of Majorca, indeed close to Palma itself. For the British Isle of Man, a cross, in the right place and of the right size, served sufficiently well for a later, far more realistic alternative to be generally ignored.

Workshop practice
Turning now to the other side of the story - the chartmakers' viewpoint - there must have been obvious benefits from those same memorable island shapes. Whereas the overall coastal outlines would have been transferred by some tracing method (probably pouncing), that did not apparently apply to the smaller islands, and certainly not to the numerous islets. Their real shapes would not have been distinctive in most cases and, had an attempt been made to reproduce those, the accuracy would have been lost through constant hand-copying. But, by giving some of those islands their own distinctive shape - often geometric and symmetrical or formed of flowing curves - with others represented by certain simple, repeated forms, drafting would have been significantly speeded up. After a while, the chartmaker would have been able to draw in most, if not all of them from memory.

A feature that has not, seemingly, been focused on before are the small hydrographical details, in red or black ink and red paint. An approximate count of those suggests that a typical chart might have had up to 3,500 such indications. In some cases those are pointilliste arrangements of dots (red for a sandbank, black or brown for a reef) which did not need careful copying. But the majority of those features were precisely positioned and remained broadly constant in their shape. These hydrographical details have fallen beneath the notice of historians but if anyone sat down to copy a chart they would soon appreciate that they constituted a significant part of the overall workload.

It is hard to see that a sailor would have been able to make much use of those hydrographical indications, since, for any real meaning, the scale would have had to be much magnified. Yet the chartmakers persisted with them. Why?

The answer - and again modern perceptions were likely to overlook it - is surely that, to the medieval mind, faithful copying was an imperative enforced by the weight of tradition. We call them 'chartmakers' but almost all were no more than chart copyists, at least as far as the core regions repeated from the earliest charts were concerned. If there was any hierarchy in the perceived value of portolan chart features, it was not what we would have expected. Grazioso Benincasa thought it was vital to place every rock in its 'correct' place but was not too concerned if the arrangement of his atlas sheets meant that one or two of the final Portuguese discoveries in west Africa had to be omitted for lack of space.

Because copying was not selective, the cheapest and most luxurious charts are essentially the same beneath the skin. Strip away the lavish ornamentation from the Catalan Atlas and you will find the same hydrographical details and the same complement of place-names. Anyway, how would they have known which place-names to leave out, or which rocks to omit, when making a rudimentary chart?

This lack of ambition, imagination, creativity, or any attempt to produce work that was better than their master's, is likely to prompt criticism today. But that conservatism was what allowed the portolan charts of the Mediterranean and Black Sea to survive for so long. Only by insisting on the careful training of apprentices and an unquestioning obedience to the authority of the workshop pattern could the charts have avoided the corruption that would have inevitably followed from any careless copying. This would have applied particularly where small hydrographical shapes had to be transferred by hand and eye.

Only by attempting to look over the shoulder, as it were, of someone - perhaps an apprentice - actually copying a chart can we hope to shake off our own values and experience so as to see it through his eyes. For the chartmaker, it (or the part he was dealing with) was one indivisible whole that had to be reproduced precisely, down to the smallest details, without adding or omitting any elements (except illustrative ones), and without lavishing extra or less care on some features than others. Certainly, each master practitioner had his own distinct model and could make changes to it, but the differences rarely affected the underlying content. Likewise, toponymy - the only feature of the early portolan charts that does show elements of dynamism (being presumably set out on a different workshop pattern) - can be a good pointer to authorship, as can another, superficial element, the choice of island colouring.

Colour
Island and estuary colouring is dealt with in the 'Colour and Shape Analysis' (C&SA), a sequence of Microsoft Word tables with accompanying commentary. It comprises a careful examination of about 100 features relating to 51 geographical entities found on virtually all the works produced up to 1469, and on a selection thereafter. This comprehensive survey allowed conclusions about the different colouring patterns of individuals, centres and periods, while also assisting in the attribution of works lacking a signature.

Toponymic development
The 1987 Chapter relied heavily on an investigation into toponymic innovation, which, for reasons of space, could only be summarised there. The DVD accompanying Ramon Pujades's notable study of 2007 provides researchers with unparalleled access to legible scans of almost all the charts produced before 1470. None of this new work would have been possible without that. As a result, a Table of 'Significant Names' has been compiled displaying the data used in 1987, but much revised and extended to 1600 (and even beyond). Its information about the chartmaker on whose dated work each of the 1,800 names was first seen, coupled with the apparent date of its subsequent disappearance, has spawned a suite of analytical tables.

The story is a mixed one of stasis and change. More than three-quarters of the names seen on the early-14th-century work of Vesconte were still there in 1600. Yet new names can be found on the work of all the 16 chartmakers who signed and dated their productions up to 1440. Then again, a massive toponymic injection by the Vescontes is followed by a steady decline in the rate of innovation until, counter-intuitively, there is a marked increase (mostly associated with the Oliva family) in the second half of the 16th century. Likewise, with discarded names there seems to have been a matching process of what could be a mass extinction around 1600, just when the charts' relevance might have been thought nearing its end in the face of printed alternatives.

Those seeking clear patterns will sometimes be frustrated by findings that undermine such certainties. For example, over a quarter of the names that Vesconte introduced after his earliest productions can be seen on the 'Compasso de navegare', dating probably from about 60 years earlier, while more than 10% of those supposedly 'new' names are found on the even earlier portolano, the 'Liber de existencia riveriarum'.

That a handful of those 'precursor names' seem first to reappear in the 15th or even 16th centuries is just another illustration of occasional toponymic intermittency, sometimes involving a century or more. The time-lag between chartmaking centres, particularly the much-delayed incorporation of some 14th-century Venetian names into Majorcan charts, highlights the separatist elements that co-existed with many shared traditions. Why Vallseca and Roselli decided to take in those names and then did so on at least seven separate occasions is just one of the continuing portolan chart mysteries.

It has been widely assumed that, since they were a tool of mercantile navigation, portolan charts would reflect trading patterns in the areas they covered. Evidence from toponymic changes, at least in the 14th century, provides little support for that. Instead, what shines through is 'propinquity': the Venetians' greater knowledge of, and interest in, the Adriatic, and an equivalent focus for the Catalans and Genoese on the seas to the west of Italy.

Why names were added or rejected - and perhaps a small majority refer not to human features but to natural ones, which, by definition, could not be 'new' - remains unclear. The answers would need to be teased out, piecemeal, via detailed local research, though much may anyway have depended on chance.

During 2013 two new developments took place. First, the 'Table of Significant Names' was expanded from 1,800 to 2,800 names, with the addition of less usual names. A number of those proved, surprisingly, to be emphasised in red. This Excel spreadsheet also supplies transcriptions of the two early portolani, 'Liber de existencia riveriarum' and 'Lo compasso de navegare', as well as the earliest surviving charts (though their dating is now controversial), the Carte Pisane and the Cortona Chart.

Second, a comprehensive study - the first of its kind - was made of the incidence of red names over the three centuries between Vesconte and the late 17th century. These are worthy of special attention because red was used to emphasise the importance of the place - and almost all referred to human geography not natural features. 630 such names were identified on 75 works (with a further 60 checked selectively). The results have been set out in detailed listings and analytical tables. Among the unexpected findings it that the number of red names seen uniquely on the work of an individual chartmaker is considerably larger than the total of such toponyms seen regularly over the period up to 1600. It also emerged that 17% of the red names not noted until after 1313 appeared thus when first seen, i.e. they were not 'promoted' black names. More than a quarter were found uniquely in the work of a single chartmaker, which, if confirmed by further studies, would provide researchers with a number of toponymic 'signatures'.

Coda
These pages build on my earlier publications - the chapter in Volume 1 of The History of Cartography (1987) and the Census of 1986, both concerned with charts produced before 1501. The 'Chapter' update page draws attention to some of the valuable features in the outstanding (but un-indexed) Pujades books of 2007 and 2009. A new Census, set out on an Excel table, links to descriptions of the handful of works that have surfaced in the past 25 years, and which occasionally still do (usually as binding fragments).

Benincasa is the subject of a separate study, which first identifies his 'visual signature' and then uses that to assess the authorship claims of related works. One part of that detailed analysis leads to a new understanding of the transmission of Portuguese west African discoveries to Mediterranean chartmakers.

A provisional index is provided to the available illustrations of portolan charts after 1469. This should assist future researchers.

Finally, an attempt has been made to produce a comprehensive bibliography of studies relating to portolan charts, mainly those published since 1986.

While it is hoped that these pages will have illuminated some aspects of the 'mystery' of portolan chart production, much uncertainty remains. For that reason some pointers have been suggested for possible future research.

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