The World of Gerard Mercator: The Mapmaker Who Revolutionised Geography

Ptolemy’s geographic writings are filled with errors of fact, many of them, as he engagingly admitted himself, due to a lack of basic information. Some, such as the “great southern continent” that he believed must balance the world on its axis, would endure, like the fabulous creatures described by Herodotus and other Greek writers, for centuries after Mercator.

For all its shortcomings, though, the rediscovery and publication of the Geographia in the West laid the foundations for the work of the great cartographers of the sixteenth century. The book traveled with Columbus to the New World; when Mercator compiled his great world map of 1569, he began with Ptolemy’s calculation of the position of Alexandria. The Geographia was still being treated as the ultimate authority fourteen hundred years after its author’s death. It shows a man trying to apply scientific methods to achieve a precise, objective representation of the world in a way that was unique in his time, and remained so until Mercator’s day.

IN THE EAST, the scanty records and remains of the work of the Chinese suggest that they had their own impressive tradition. Around the third century AD, a government minister of works named Phei Hsiu set out official principles for the making of maps under the Chin Dynasty. The most important of these was that they should be constructed on a rectangular grid in order to create a consistent scale and locate places accurately. There is no evidence that Ptolemy’s thinking had reached the Far East – a grid system had been introduced in China some two hundred years before Phei Hsiu by Ptolemy’s near-contemporary Chang Heng, an astronomer royal of the Han Dynasty.* He wrote of a spherical world suspended in infinity, like a yolk in an egg, and the system he introduced of building up a map by equal squares – “casting a net over the Earth,” in a contemporary phrase – was the basis of Chinese cartography for centuries.

Chang Heng’s grid made no allowance for the curvature of the Earth, and it is hard to know from what is left of ancient Eastern cartography whether his image of a spherical world had any effect on current thought. There are no indications that early Chinese mapmakers realized the world was a sphere, that the lands they were mapping were consequently curved, nor whether the challenge, which still fascinates cartographers, of representing such a three-dimensional world on a flat surface had even occurred to them as a problem.

In the Islamic world, Arab mapmakers drew on the ideas of Ptolemy and the Greeks to develop their own traditions. By the eighth century, they were compiling maps for overland diplomatic missions to China, military campaigns, and trading expeditions; the tales of Sindbad the Sailor, dating from some two hundred years earlier, are ample evidence of their seafaring traditions. Unlike the work produced by medieval monks in Europe, their maps seem to have been designed for use as much as for study, but they were still based mainly on copies of older European originals. There are early versions of the T-O maps, with south at the top and Mount Sinai in the center and, slightly later, more distinctively Arab interpretations in which a disk-shaped world, surrounded by water, is pierced from the east by the Arabian Gulf and the Red Sea, and from the west by the waters of the Mediterranean.

Later mapmakers of the tenth and eleventh centuries were often slave dealers or traders, making their way north to the shores of the Caspian Sea and up the Volga River deep into the heart of Asia. Asian tribesmen, Russians, Norsemen, and Arabs would meet on one of the medieval world’s great trading routes, exchanging goods, knowledge, and ideas.

One account, by the writer Ibn Haukal, author of The Book of Roads and Kingdoms, which contained a map of the Islamic world as it was then known, described a meeting toward the end of the tenth century with the great Arab cartographer al-Istakhri. “He showed me the geographical maps in his work, and, when I had commented on them, he gave me his work with the words, ‘I can see that you were born under a lucky star, therefore take my work and make such improvements as you think fit.’ I took it, altered it in several particulars, and returned it to him.”6

There was cooperation not just between individuals but between cultures. One of the greatest of all the Arab cartographers, Muhammed al-Idrisi, was born in Morocco, studied at Cordoba in Islamic Spain, and worked at the twelfth-century court of the Christian king Roger of Sicily. There, he produced several world maps that drew directly both on Ptolemy and on the observations of Arab travelers, and which were still being used as models by Islamic cartographers four hundred years later. Among them were a large rectangular map in seventy sheets, and a smaller, circular map, similar to the T-O maps of the West, but incorporating curved parallels, which suggest that al-Idrisi was aware of the spherical shape of the world. The maps and sources that he used are lost, but the geographic detail he provided was far in advance of anything that was being produced by the copyists in Europe’s monasteries. Al-Idrisi’s representation of Spain, for example, with the northern coast of Africa, the Straits of Gibraltar, and Bay of Biscay all clearly discernible, is far more detailed than the stylized version presented around the same time by European mapmakers. When Al-Idrisi described Britain as “a great island, shaped like the head of an ostrich,” and the peninsula of Cornwall as “like a bird’s beak,”7 he had evidently been studying more accurate maps than anything available in Europe.

DESPITE ITS ULTIMATE INFLUENCE in Europe, for hundreds of years after publication of the Geographia, Christian scholars turned their backs on Ptolemy’s knowledge. With the fall of the Roman Empire, the original manuscripts that Ptolemy had written in the second century were lost and forgotten. For the medieval scribes of the early Church, the old T-O maps compiled in the centuries before Ptolemy had the great advantage that they could easily be adapted to place the holy city of Jerusalem at the center of the world, as the Bible itself decreed.8 For them, as for the Greek philosophers, the sea was a fitting symbol to represent the mysteries that bounded man’s little area of knowledge on every side. What had not been established by exploration was supplied by imagination or faith; the maps that the medieval Christian scholars drew were therefore inaccurate, impressionistic expressions of belief, not descriptions of fact.

Some of these great mappaemundi, the medieval pictures of the world, were also works of art of staggering beauty. Most of them are lost, but in the English cathedral city of Hereford, it is still possible to glimpse the vision of the world that was in men’s minds on the eve of the age of discoveries. The great Hereford mappamundi dates from the last years of the thirteenth century.9 Even after a visitor to the cathedral has puzzled out the fact that, as on almost all early maps, east is to the top, and has spotted the outline of the Mediterranean Sea that divides the world down the middle, the coastlines and landforms are almost unrecognizable. There is no mistaking the traditional T-shape of great waters surrounded by the O of the ocean, although the lands are threaded with rivers. The British Isles clutch grimly to the perimeter of Europe, twisted and misshapen; instead of the familiar boot shape of Italy, there is a bloated peninsula, dotted with apparenty random cities and ribbed with unknown rivers. The names of Europe and Africa are transposed, probably a mistake by the copyist. Indeed, the map as a whole seems to be sketched more in hope than in conviction. Any modern classroom could produce a dozen more realistic views of the world. Ptolemy would have scoffed.

Yet the Hereford mappamundi has its own confidence, as befits the only complete wall map of the world known to have survived from the Middle Ages. It speaks the language of another age. What were once its bright colors are faded and browned into a dull ochre that challenges the eyes, while the drawings that crowd the map seem almost to jostle each other aside; it takes a while to focus on them individually, to see the delicacy and precision with which they are sketched in. Carefully drawn towers and turrets mark some of the cities of which the map-maker had heard: The familiar names of the Bible are clustered around Jerusalem, and, closer to home, Paris, Ghent, and even Hereford itself are marked. But it is a work to be interpreted, rather than simply consulted; a statement of belief.

Medieval library catalogs show that there were few monasteries or noble palaces without such maps in their stores of manuscripts. Charlemagne, at the end of the eighth century, had plans of Rome and Constantinople engraved on silver tablets among a comprehensive collection, and most great libraries would have included maps of the Holy Land as well as the great mappaemundi – triumphs and baubles for the rich and mighty, and reminders for the humble poor of their place in the great scheme of being. Few survived. A sister-map of the Hereford mappamundi, the Ebsdorf map, was rediscovered in a Benedictine monastery in the German town whose name it bears after being lost for six hundred years, only to be destroyed by Allied bombing during World War II. Now it survives only in modern copies and photographs. The history of cartography is the tantalizing study of what has been left behind.

The Hereford mappamundi

Hereford Cathedral Library, Hereford, England

The worldview of the mappaemundi encompassed the soul as well as time and space. The Hereford map, for example, shows not only the towns of the Holy Land but also the expulsion of Adam and Eve from Eden and Noah riding on the waters of the Flood. It admits no conflict between geographic accuracy and religious faith: The holy city of Jerusalem stands unchallenged at the center of the world, while Paradise itself is shown far away in the apparently unreachable East, a round island circled by flames that warn the importunate traveler not to dare too much.

The mappaemundi may have been used for planning journeys from town to town across Europe – marks over the great central city of Paris on the Hereford map suggest that fingernails may have traced a route through it at various times – but it mattered little to the mapmaker that the shape of the coastlines should be so inaccurate, or that the whole map should have been shoehorned so ruthlessly into an all-embracing circle of ocean. Much more important, from his standpoint, God had to be shown overseeing the whole of his kingdom, and the fabulous creatures described by the ancients, such as the bonnacan, with its bull’s head, horse’s mane, and ram’s horns, the screaming mandrake plant, and the death-dealing cockatrice, needed to be faithfully represented to demonstrate the awesome variety of his Creation.

The Hereford mappamundi laid out a world at once mysterious and threatening, where the only hope of safety was to be found in the majestic figure of Christ that dominates the map. To criticize it for inaccuracy would be as foolish as to find fault with Picasso’s famous painting as a street guide to Guernica. Yet for the rapidly growing world of the fifteenth and sixteenth centuries, the mappaemundi were quickly proved inadequate. A new geography was needed to enable sailors to plot a reliable course across the oceans and to represent the world they were revealing.

Three events in the half century or so before Mercator’s birth made his achievement as a cartographer both possible and necessary. The first was the rediscovery of the geographic writings of Ptolemy, brought back into Europe after hundreds of years; the second was the development of printing, which meant that Ptolemy’s ideas could be spread more quickly and efficiently than the monks who had copied them by hand could ever have dreamed; and the third was the voyage of Christopher Columbus, who, looking for Asia, discovered America.

Other explorers had made great discoveries around the coast of Africa and in Asia about lands that were already dimly known about, but Columbus’s voyage proved that there really was a world elsewhere. The looming shadows that had marked the boundaries of geographic knowledge ever since man first looked about him were beginning to part, to reveal a reality far different from anything the ancient scholars had imagined.

Chapter Two Forgotten Wisdom

FOR THE SCHOLARS of fifteenth–and sixteenth-century Europe, who looked on the past with reverence, the rediscovery of Ptolemy’s writing in the early fifteenth century was a revelation and an inspiration. The task of translating the Geographia into Latin from an original Greek manuscript in Byzantium was begun by the Byzantine scholar Manuel Chrysoloras and finished in 1406 by his pupil Jacobus Angelus in Tuscany.

In the Arab world, the Almagest and the Geographia had both been known by then for some five hundred years, and practically every Islamic cartographer either mentioned, quoted, or silently borrowed from what they called the Kitab gagrafiya (Book of Geography). However, not until the fall of Byzantium to the Turks in 1453 did refugees bring the manuscripts to the West in any numbers. Monks in Florence translated them from Greek into Latin and wrote them out painstakingly by hand, making copies available over the following years, first without maps, then with regional maps, and finally with world maps drawn according to Ptolemy’s recommendations. At the time of Mercator’s birth, they were still fresh and exciting – a philosophical framework into which the new discoveries about the extent and shape of the world could be incorporated.

Ptolemy’s books had been copied and copied again in the Arab world for centuries prior to the time they resurfaced in Europe; by then, they almost certainly included the additions and amendments of generations of nameless and unknown thinkers. Nonetheless, however much or little of them had actually been written by Ptolemy himself, they were a virtual synthesis of classical scientific knowledge.

The Geographia concentrated on the arts and skills of mapmaking, discussing the comparative merits of flat maps and globes, and arguing through the mathematics of how a map should be constructed and how the world could be divided into the three continents of Europe, Asia, and northern Africa. The great undiscovered continent that Ptolemy believed lay to the south turned the Indian Ocean into an inland sea, and in the East, the known world petered out in the unexplored lands beyond the Ganges. West of the Pillars of Hercules, at the mouth of the Mediterranean, of course, he described nothing but sea and a few scattered islands.

Fresh versions appeared year by year, with cartographers adapting and expanding Ptolemy’s work. An edition was printed in Cologne in 1475 without maps; only two years later, the interest and the technology existed to prepare a version in Bologna that included twenty-six copper engravings based on Ptolemy’s text. By the time Mercator was working, the book’s reputation was established among scholars, even though the great voyages of the fifteenth and sixteenth centuries were already demonstrating its limitations.

For all the dedicated work of the monastic copyists, it was the development of printing that allowed Ptolemy’s work to be widely read in Europe. The impact of Johannes Gutenberg’s first press with movable type in the 1450s is hard to exaggerate. In the Low Countries alone, more than four thousand different books were produced in the first decades of the sixteenth century; there were in excess of 130 printers there, half of them in the thriving city of Antwerp.

Ptolemy’s Geographia was only one of a range of classical works that flooded off the new presses to feed the public’s apparently insatiable appetite. As these books were shipped around the continent, they invigorated and inspired learning not just in the palaces, monasteries, and great houses that had always collected rare and expensive manuscripts, but also in the studies of poor students. Without the explosion of printing, Mercator would never even have seen many of the books that enthused him at Leuven. He would certainly never have gathered around him the personal library in which he delighted in the German city of Duisburg.

However, for all the excitement that the rediscovery of Ptolemy’s Geographia stirred up, his three continents soon could no more be accepted as they stood than could the old T-O maps or the mappaemundi. There had been rumors for centuries of scattered islands far away to the west, but no one had any idea of the vast extent of the newly discovered land. Just twenty years before Mercator was born, the discovery of America had revealed a new world of which Ptolemy and his predecessors never dreamed, confounding the ancient view that the Earth was limited to the three continents of Europe, Asia, and the strange and mysterious Africa.

While the actual extent of the world would have astonished the ancients, its round shape had been known since well before Ptolemy’s time. Various early Greek philosophers had produced detailed arguments to prove that the Earth was cylindrical, disk-shaped, or rectangular, that it was cushioned in compressed air, or that it was floating on water. Yet by 250 BC, Eratosthenes of Cyrene, one of the scholars who devised a rudimentary grid of latitude and longitude, had not only accepted the idea of a spherical world but had studied the stars to calculate its circumference.1

Strabo, another Greek geographer and historian, who worked before Ptolemy in the library of Alexandria in the last century BC, had a severely practical turn of mind. The world could be represented on a globe, he declared, but the globe would have to be ten feet across to show all the necessary detail. The work of Ptolemy himself a century or so later in devising projections shows that he had no doubts either about the curvature of the Earth. For accuracy, he concluded, there was no substitute for a globe.

Ptolemy had described in great detail how it should be done, with the globe suspended between two poles connected by a semicircle, which should almost touch its surface. Such an arrangement, he wrote, had advantages and disadvantages when compared to his own efforts at working out a way of projecting a map onto a flat surface: “It preserves the world’s shape, and avoids the need for any adjustment of it, but it hardly provides the size needed for containing most of the things that must be marked on it, nor can it allow the entire map to be shown from one vantage point.”2

Like his books, Ptolemy’s endorsement of the globe was lost to Europeans in the Middle Ages. There are tantalizing mentions in classical literature of various globes, including small representations of the Earth enclosed within glass spheres which showed the constellations, like the pair Charles V, the Holy Roman Emperor, would later demand from Mercator. But if the Greeks or Romans ever made large detailed models of the spherical Earth, in line with the recommendations of Ptolemy and Strabo, none of them survived. European craftsmen produced armillary spheres in which concentric metal rings would demonstrate the supposed motion of the planets around the Earth, but they showed no interest in the idea of a terrestrial globe.

The Arabs, on the other hand, turned Ptolemy’s words into reality. Many of them used his Almagest rather than the Geographia and showed the stars, not the Earth, in their work. In Florence’s Museum of the History of Science, there is an engraved metal sphere about eight inches in diameter, with 1,015 stars marked on it according to Ptolemy’s descriptions, made by Ibrahim ibn Said al-Sahli al Wazzan with his son Muhammed in Valencia, in Moorish Spain, in the late eleventh century.

Such magnificent celestial globes were often carved on brass or silver, intended for a study rather than the navigator’s desk, but the Arabs must have made terrestrial globes as well. None survives today, but Christopher Columbus said in his ship’s log that he had seen globes of the world on which the island of Cipangu, or Japan, was marked.

The Arab globes were also studied by Martin Behaim, a Nuremberg traveler and adventurer who set out to copy the technique and manufacture a globe of his own toward the end of the fifteenth century. Behaim claimed to have sailed the coasts of Africa with the Portuguese explorers, and to have seen the globes at the Royal Observatory, which had been established in about 1420 by Portugal’s Prince Henry the Navigator at the southern port of Sagres.3

One advantage that neither Strabo, Ptolemy, nor their Arab imitators had mentioned was that the globe offers a dramatic way of demonstrating the circularity of the Earth to a layman – an investor, for instance, who might be persuaded to put money into an expedition. The Portuguese had demonstrated that there were riches to be won in the East, and in order to show the wealthy financiers of Germany how easily the Indies could be reached by sailing west, Behaim constructed the first modern globe known to have been produced in Europe. It was intended not for scholars or sailors but for bankers.

Behaim, the son of a German nobleman, had been packed off to Portugal as a young man to gain experience as a businessman, but had spent more time there among the sailors and navigators around the docks than in import and export. He had a healthy disrespect for authority – in his youth, he was said to have served a month in prison for dancing at a Jew’s wedding during Lent – but he also had a shrewd commercial eye. He was fascinated not only by what he had seen of the voyages of discovery but also by Prince Henry’s Arab globes.

None of those globes is known to have survived, but the Arabs had proved that Ptolemy’s theory worked. A globe to show how the western ocean lay between the continents of Europe and Asia was clearly the way to impress a skeptical audience with the practicality of sailing west to reach the Spice Islands in the East. The Portuguese controlled the passage around the southern coast of Africa, and huge costs were involved in the ancient overland trails from Asia through Arabia to the Mediterranean. The globe – which Behaim called his erdapfel, his earth-apple – was a striking demonstration of another route.

Today, Behaim’s brainchild is the most famous exhibit in Nuremberg’s Germanisches Nationalmuseum,4 darkened by age and scarred by the attentions of well-meaning “restorers” in the nineteenth century – the oldest terrestrial globe in the world. It was a scientific wonder, an artistic triumph representing the best thinking of Behaim’s age about the shape of the world – and a commercial dead end. Unlike the globe manufacturers who followed him in the sixteenth century, Behaim could not profit from selling examples of his creation; his globe was, unavoidably, unique. He lived before the development of printing techniques enabled artisans and mapmakers to create limitless copies of their work, and his map had to be painted by hand onto sheets of thin, fine leather after they had been stuck to a twenty-inch papier-mâché shell and mounted on an elegant wooden stand. It was never designed for navigation. Apart from the equator, a single meridian, and the Tropics of Cancer and Capricorn, there were no longitudes and latitudes marked on it, although Behaim did include the constellations of the zodiac and an array of forty-eight flags of European nations and noble families, fifteen coats of arms, and forty-eight portraits of kings and rulers. The globe was a tool of commerce, and to catch the interest of the Nuremberg merchants, Behaim incorporated lengthy descriptions of what merchandise could be purchased in the various islands of the Far East, and how trade should be conducted. For the artist Behaim paid to paint his globe, it was a miniature masterpiece. But however much the burghers of the town admired the piece, it could never be reproduced, except by starting from scratch with a new map.