The World of Gerard Mercator Read online

  The Phoenician capital Tyre, on the coast of what is now Lebanon, had trading links that extended through the entire eastern Mediterranean and far beyond. The places Ezekiel named in these verses as the Phoenicians' trading partners in the sixth century BC were in central Asia, southern Arabia, Armenia, and the coast of Spain, and his list of the merchandise— slaves, animals, manufactures, luxuries, and other goods— that appeared in their marketplaces lasted for more than twenty biblical verses. Travel and its commercial benefits were common enough; from the earliest times, explorers and adventurers had returned with exotic cargoes, but the stories they brought back were confused and unreliable. The island of Taprobane that Ptolemy described was said to dwarf the Indian peninsula that lay to its north, while the great medieval map of the world, dating from the late thirteenth century and still on display at Hereford in England, shows two distinct Niles, one running into the eastern Mediterranean, the other snaking across almost the whole width of the African continent. The accounts of the early adventurers were neither more nor less believable than the grotesque creatures with which ancient Greek and Roman authors loved to people the unknown places. There was no agreed view of the world; anything was possible. Travelers had no reliable or accurate way to record what they had found, to set it out for people to see. To become part of a shared image of the world, their stories had to be written down, described, and mapped.

  Today, the oldest so-called maps look like little more than a few carved scratches, their meaning lost with the civilizations that created them. About four thousand years ago, craftsmen near the present-day village of Bedolina, some ten thousand feet high in the Italian Alps, set about carving the rock with rough bronze or iron tools. They drew pictures of animals, daggers, and suns, much as their cavemen ancestors elsewhere in Europe had done ten thousand years earlier. But the artists of Bedolina also produced one of the first known maps. The Mappa di

  Bedolina is approximately four yards wide and six yards high, an ambitious patchwork of carved lines and symbols, with a series of crudely drawn rectangles, most of them filled with carefully spaced dots and linked with snaking irregular lines. They seem to represent fields with paths, rivers, or irrigation canals running between them—a graphic illustration of a cultivated landscape in the Valley of Valcamonica below. Their carvings could have had some religious or magical purpose, but after four millennia, we can only guess at what it might have been. Armed figures, huts, and shapes like ladders were added to the map hundreds of years afterward, maybe adapting it for new mystical or ceremonial rites in a mixture of religious faith and straightforward observation that was to characterize mapmaking through the ages.

  Centuries later, merchants and travelers who were pushing farther and farther afield in the search for new markets brought back garbled reports of the mighty Rivers Don and Nile running south out of Asia and north out of Africa to form a T-shape with the well-traveled waters of the Mediterranean. The waters of the ocean were then thought to surround the world in a gigantic O, leading to the creation of the so-called T-O maps, which represented for ancient Greek, Roman, and even Arab seamen an agreed image of the outline of the world.

  THAT WAS THE WORLDVIEW Claudius Ptolemy inherited as he worked in the great library of Alexandria around the middle of the second century AD. His name appropriately linked the Greek-Egyptian Ptolemy with the Latin Claudius, for Alexandria was a cosmopolitan place, more than five hundred miles from Greece, under Roman rule, and yet at the heart of Greek civilization. The city, with its port and its great lighthouse, was a triumphal expression of Greek civilization and Roman power. Like Antwerp in Mercator's day, it was one of the world's great cultural and commercial crossroads, with mineral ores and spices ferried down the Nile from the depths of Africa and along an elaborate network of canals, then traded along the waterfront with the day-to-day cargoes that had been brought into harbor from the busy eastern Mediterranean. Sailors and merchants brought with them tales of distant lands like Taprobane, half-digested stories that might conceal a thin vein of truth for scholars trying to extend their grasp of the unknown world. Busy ports have always been the mines of geographers; travelers' gossip was the unsmelted ore of exploration for Ptolemy, as it was to be for Mercator.

  The merchants brought wealth to Alexandria as well. In the days of its greatness, the story went, the buildings contained so much glistening marble that a tailor could thread his needle by the reflected light of the Moon. The library where Ptolemy worked, with its collection of some seven hundred thousand manuscripts in Hebrew, Greek, and Egyptian, was one of the most obvious expressions of that wealth. Just as the merchants in the port haggled and bargained over the commerce of the mightiest empire the world had ever seen, so Alexandria's scholars swapped ideas and theories in the library and the museum associated with it.

  There are no surviving original manuscripts of Ptolemy's work, and hardly any facts known about his life, but it would be hard to exaggerate the effect of his books on the generations that followed him. For centuries after his death, they were largely forgotten in the West, but to Mercator, the writings of Ptolemy represented the fount of ancient knowledge, the standard by which new discoveries and theories should be measured. Apart from the eight books of the Geographia, the Al­magest set out Ptolemy's views on astronomy and the place of the Earth at the center of the universe, while his various other writings encompassed mathematics, music, and history.

  Other writers had concentrated on stories of the wonders that lay at the farthest reaches of knowledge, but Ptolemy's main interest lay in establishing a reliable and coherent system for showing the spherical Earth on a flat sheet of paper. Philosophers could only suggest what form the Earth took, while travelers either by land or by sea could do little more than estimate distances—in both cases, their contributions were merely elegant guesswork. The generally accepted image of the land surrounded and limited by the ebbing and flowing waters of the sea suggested a comfortingly finite world. Ptolemy raised the possibility of a world beyond those boundaries, basing his conclusions not just on the arguments of the philosophers and on the reports of travelers but also on exact astronomical measurements.

  Ptolemy saw geography as a mathematical enterprise, a matter of measurement and calculation rather than the simple telling of stories. Like Mercator some fourteen centuries after him, he designed and made instruments for measuring angles and altitudes in the heavens; his Geo­graphia includes descriptions of a brass astrolabe and a quadrant for calculating the height of the Sun in the sky.

  Ptolemy knew the true location of a place could be fixed by taking precise sightings of the stars. The Geographia therefore included a catalog of some eight thousand place-names, rivers, mountains, and peninsulas, each of them with its position defined by degrees of latitude and longitude. It is a work of staggering ambition and exactitude—the first time anyone had attempted to use coordinates in such a precise way. Many of the observations Ptolemy needed to make the calculations had already been taken, but to place cities in remote or unexplored parts of the world, he had no choice but to rely on traditional accounts and the estimates of travelers. In such a case, he said, the mapmaker should use his judgment as to what figures to use, "deciding what is credible and what is incredible."4

  It is impossible to know whether Ptolemy drew any maps to go with his Geographia. The illustrations that adorned medieval versions of his books were additions by later copyists working to his descriptions and coordinates, but in them his worldview, with the traditional three continents of Europe, Asia, and part of Africa, can clearly be recognized. Taprobane is grotesquely out of proportion in comparison with the half-formed India that lies to its north, and the coastline of the Far East is clearly drawn largely from imagination, but the Arabian peninsula and the whole of the Mediterranean basin are presented in some detail.

  Perhaps most important of all, though, Ptolemy left open the possibility that there were more lands to be discovered beyond the extent of his own knowledge. Wher
e the Romans and Greeks who came before him had been content to keep their studies inside the limits of the habitable world, his interest was in the Earth as a whole, and geography, for him, was no more or less than the art of making maps. "It is the prerogative of Geography," he said, "to show the known habitable earth as a unit in itself, how it is situated and what is its nature; and it deals with those features likely to be mentioned in a general description of the earth, such as larger towns and great cities, the mountain ranges and the principal rivers."5

  The circle of seas that surrounded the Earth in the early T-O maps was one way of suggesting a round world, but Ptolemy's was the first serious attempt to deal with the problem of projection. He described two possible solutions, based on a simple rectangular grid that ancient Greek philosophers had already devised, but adapting it to take account of the fact that the Earth was curved, not flat.* The systems he suggested were, as they had to be, a compromise, and one which worked satisfactorily enough within the limits of the known world. Even in the sixteenth century, most maps were still produced on grids that were simple adaptations of Ptolemy's projections. Mercator's greatest achievement would lie in rethinking these fifteen-hundred-year-old proposals.

  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 in-troduced 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 Bool{ 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,"7he 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.8For 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.9Even 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 apparently 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 mapmaker 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.