by Peter Watson
No less Christian in intent were the ‘zone and climate’ maps which, by tradition, divided the earth into five climatic zones–a northern extremely cold zone, a temperate, habitable band further south, a central, uninhabitable ‘torrid zone’ around the equator, and two further zones to the south, a temperate one, and a frozen one, echoing those in the north.36 The idea of an impassable torrid zone, in particular an impossibly hot sea, seems to have been a Greek idea originally, taken up by the Christians. The effect of this was to suggest that a northern sea passage was impossibly cold, whereas a southern one was impossibly hot. This implied that the only way to travel the earth was by going west.
Early in the fifteenth century, the Geography of Ptolemy, the second-century geographer, was rediscovered. The Greek text was brought to the West by Chrysoloras and made generally available through a Latin version prepared around 1409 by Jacopo Angelo de Scarperia.37 This work was supplied with maps, thanks to Cardinal Guillaume Fillastre, and the so-called ‘new geography’ became immensely popular (though there was some doubt about the very great size Ptolemy attributed to Asia).38 Gatherings of scholars, in particular for the 1450 Papal Jubilee in Rome, encouraged more and more maps that made use of Ptolemy’s ideas. One effect of these maps, which has provoked great interest among scholars concerned with the mind-set of Columbus, was to minimise the size of the globe. Though Columbus didn’t accept the shortest estimates available, Samuel Morison, in his great life of the explorer, shows how, from a reconstruction of a chart by Paolo Toscanelli, a Florentine physician who was in correspondence with Columbus, fifteenth-century mapmakers had taken on board Marco Polo’s observations, namely that Cipangu (Japan) was about 1,500–1,600 miles off the coast of China, with many islands in between. On this reckoning, Polo’s Zaiton (the port he left from, when he journeyed home) might lie ‘a little to the east of present day San Diego, California’.39
Valerie Flint’s reconstruction of Columbus’ known reading shows that, in addition to Italian, he was adept at Latin, Castilian and Portuguese and that his books–many heavily annotated to the point of defacement–fell into two broad areas. He was, as the remarks at the beginning of this chapter underline, fascinated by Asia, by the exotic people and treasures to be found there, which all reinforced his conviction that he would one day find a new route to the East. The less copious aspect of his reading was given over to how new countries might be governed and administered. This was against a general background that you would expect for an explorer—a grounding in astronomy, arithmetic, geography, geometry, as well as history and philosophy.40 It would appear that Columbus did not read widely, but he did read deeply. There survive five books heavily annotated by the admiral. These include the Imago Mundi of Pierre d’Ailly (1350—1420, bishop of Cambrai, then cardinal) which was printed in the early 1480s and claimed that in parts of the world it was day for six months followed by night for six months.41 Columbus’ copy contains 898 postille, or annotations. A second book, the Historia Rerum Ubique Gestarum, by Aeneas Silvius Piccolomini (Pius II, pope 1458—1464), had 862 annotations, and a third, De Consuetudinibus et Conditionibus Orientalium Regionum, produced by the Dominican friar Pipino of Bologna, in the early fourteenth century, had 366 annotations. A lot of Columbus’ mental horizon can be reconstructed from these annotations. For example, we can observe Columbus as he settles on certain aspects of these books. He is very interested in the treasures they describe, in the effects of climate on human nature—he believes, for instance, that the peoples of the East, where the sun rises over them, are quicker by nature than other peoples, and ‘inclined to high enterprise and to astrology’.42 Columbus is particularly interested in any abnormalities of nature. He believes that extremes of climate may produce deformities in people, in particular cannibalism, an interest which pervades his writings. Among the monstrous and marvellous peoples, he seems to have had an abiding interest in Amazons, societies where the traditional gender and sexual roles are reversed, and where women are the leading lights. 43 He shared the feelings of many people of his age that the wearing of silk led to moral turpitude but he was fascinated by China because he believed it lay opposite Spain, across the Atlantic, with the northern part opposite Ireland.
Of course, he was interested in seafaring too, as may be imagined, and in particular ailments that might be encountered at sea. Remedies for kidney stones consist of a sea scorpion soaked in wine, or water-snakes’ livers, or sea nettles also soaked in wine. Perhaps the most unexpected aspect of Columbus’ reading was Plutarch’s Lives, which was translated fully into Latin only in 1470.44 As well as showing an interest in history, and historical biography, it seems that Columbus was looking for models of government that might be needed if he did indeed find new countries.45 He noted instances of liberality and openness, the arrangements that induce fellow-feeling among citizens, and the amount of public display of wealth that is permissible.
So much was general background for Columbus. But there was a more immediate set of influences on his knowledge and thinking, and the first key figure here is Prince Henrique of Portugal, better known to history as Henry the Navigator. Henry’s interest in navigation is said to have been stimulated by the war which Portugal waged against Morocco in 1412 when, after the Portuguese victory, Henrique was more taken by Ceuta market than anything else. ‘There he saw goods that had travelled over desert routes reaching far south toward Timbuktu, in the heart of Africa, and eastward to the Red Sea. Henry came back to Portugal wondering if the ocean might not be a better highway to the south and east than the desert.’ He settled down in the little town of Reposeira to study geography, astronomy and navigation, and to interview sailors from ships that anchored in the shadow of Cape St Vincent, the south-west corner of Europe.46 It was a spot that could hardly be bettered, for he could learn from both the Mediterranean and Atlantic traditions of seamanship.47
From the Mediterranean navigators came knowledge of the compass. This had been invented in China, thanks to the practice of the Chinese of always wanting to be buried lying in the most propitious direction. (Since we are alive on earth for only a short time, but lie in the ground for centuries, graves were regarded as much more important than, say, houses.) One of the ways a correct burial was achieved was by means of a special board, on which a spoon was spun. (Spoons were possibly used because their shape roughly conformed to the Great Bear in the sky, the constellation which fixes the Pole.) As the practice developed, so more precious materials were used for the sacred spoons–jade, rock crystal, lodestone. It was noticed that whereas all other materials produced variable results, lodestone spoons always ended up by pointing south. This was the basis of the compass, which was conceived around the sixth century AD, and spread gradually to the West. It replaced the very earliest method of navigation (across open sea, that is), which was to take birds on board and release them at intervals. They instinctively knew where land was and so the sailors followed them. Among other things, this was the method used to discover Iceland.48 The great age of discovery would not have been possible without the compass.
Mediterranean ships also carried marine charts on which the course was plotted through daily records of sailing, known as dead-reckoning. These charts included a great deal of hard information, based on the conduct of regular trade. But the requirements of oceanic travel were somewhat different and this only emerged gradually. The plain fact was that the oceans were so large that the curvature of the earth became an important factor in navigation. It took time for men to realise this and it took time for them to find a solution.
The term portolano originally meant written sailing instructions but it was adapted to describe the Mediterranean marine charts. These portolano charts were hand-drawn, showing principal harbours, major landmarks and the intervening towns and ports, filled in according to experience. Their appearance hardly varies. Drawn on a single strip of parchment, three to five feet long and eighteen to thirty inches deep, the coastlines are in black, towns are in black, writ
ten perpendicular to the shoreline, with major features in red. There is little inland detail, save for rivers and mountain ranges.49 Off-shore navigational hazards are marked, as dots or crosses, but no currents, depths, or tide races are given. The main aim of the cartographers at this point was to achieve accuracy in terms of distances and no account was taken of the sphericity of the earth. This did not cause much error in the Mediterranean, because it was a relatively narrow east–west sea, where the range of latitude was small.
Beginning in the middle of the fifteenth century, however, as Portuguese explorers extended their knowledge of the west African coast, and the islands of the Atlantic, there developed a demand for charts showing these parts of the globe. (The earliest Atlantic charts were produced between 1448 and 1468.) The first technical innovation of these new charts was the introduction of a single meridian, usually that of Cape St Vincent, stretching right down the chart from top to bottom, indicating degrees of latitude. Though this was an advance, the problem here was that the portolan tradition used magnetic north rather than true north and, as exploration proceeded, this variation began to matter more and more. Some charts therefore contained a second meridian, drawn obliquely on the charts, at an angle relative to the central meridian, corresponding to the variation.50 Maps of the late fifteenth and early sixteenth centuries show the progressive discoveries that had been made: for example, the Indonesian islands and the Moluccas–the long-sought Spice Islands–were more accurately rendered.
The earliest world chart to include both the Old World and the New is Spanish, bearing the date 1500, which was drawn up by the Biscayan cartographer and pilot Juan de la Cosa, who accompanied Columbus on his second voyage. It has no latitude marker and the two halves are drawn to a different scale. In a slightly later chart, known to historians as the Cantino chart, because it was smuggled out of Portugal by a man of that name, the outline shows the whole of west Africa and even the west coast of India, based on accounts of Vasco da Gama’s discoveries, where a coastline of the New World, to the north-west of the Antilles, is clearly marked as ‘Parte de Assia’. The whole chart is headed: ‘Chart for the navigation of the islands lately discovered in the parts of India.’
But the most important charts of the period were the Spanish Padrón Real, the official record of discoveries, first produced under royal command in 1508 and kept in the Casa de la Contratació n in Seville, and continuously updated as discoveries proliferated.51 Though none of these maps survives, some based on them, produced by Diogo Ribeiro and now in the Vatican, show that the proportions of the world were being progressively better understood. The dimensions of the Mediterranean shrink to something like their true layout, and Africa and India are more accurately represented. There is still one major error: the east–west extent of Asia, which was much elongated. People still felt that Asia was not so very far to the west of Spain.52
The medieval mappae mundi, biblically inspired, with Jerusalem at the centre and a terrestrial Paradise in the east, were becoming unrecognisable by the middle of the fifteenth century. What may be called a half-way map, which shows the evolution (rather than the revolution) of ideas, is the famous world map drawn up in Venice in 1459 by Fra Mauro. This is portolan in style; Jerusalem is central, latitudinally, but displaced to the west longitudinally, so that Europe and Asia are shown in more or less their proper proportions. Parts of Africa (Ifriqiya) bear Arabic place names, and Asia is shown with a number of features first described by Marco Polo. There is a continuous ocean to the south of both Africa and Asia. The monstrous races and the terrestrial Paradise have gone.
As more of the globe was discovered, so the portolan tradition began to fail navigators in more important ways. This was mixed up with the discovery of Ptolemy’s Geography, which had attempted to cope with the curvature of the earth but at the same time posited a vast terra incognita in the south, beyond the torrid zone. It was now realised that there was no torrid zone, not in the ancient sense, and no terra incognita, at least in the sense of a whole continent connected to Africa or Asia.
The first printed map to show America, that produced by Giovanni Matteo Contarini in 1506, does show the curvature of the earth, while at the same time displaying the new world in three parts–the north joined to Cathay, the West Indies as a group of islands not far from Japan, and Terra Crucis, South America, as an entirely separate (and huge) continent in the south. A year later Martin Waldseemüller produced his famous world map, twelve sheets drawn on a single cordiform projection, with its title describing it as ‘according to the tradition of Ptolemy and the voyages of Amerigo Vespucci and others’ (this is the first map to use the word America to describe the New World). It shows the Old World landmass as occupying 230° of longitude, but Waldseemüller later abandoned Ptolemy and produced maps which showed Asia in its more or less proper proportions.53
But Ptolemy’s influence lived on in the inspiration he provided for those who sought to improve navigational techniques as the curvature of the earth came to be better understood. The first man to explore this problem was Pedro Nunes, a Portuguese mathematician and cosmographer. Though he never reached the point of actually projecting a chart, others did, in particular the Fleming Gerhard Kremer, or Mercator. Mercator was a land surveyor, and engraver, a maker of mathematical and astronomical instruments, as well as a cartographer. He was the most learned geographer of his day (he made an edition of Ptolemy, among other works), but his fame rests on his world map, which was very large, made up of twenty-four sheets.54 It was drawn up to his new projection which, though modified many times since, still bears his name. The basic principle of the map is a graticule (or grid) of latitudes and longitudes, drawn as parallel straight lines. But Mercator overcame the effect of the curvature of the earth by increasing the length of the degree of latitude on his map progressively towards the poles in the same proportion that, on a curved surface, the meridians converge. In the phrasing of the time this meant that his maps had ‘waxing latitudes’. In this way the correct relationship of angles between one place and another was preserved, and meant that navigators could plot courses as straight lines on their charts. Mercator’s projection was, in a sense, a theoretical breakthrough, in that it introduced stability into navigation without, as it were, corresponding increases in the quality of the maps on which it was used. Longitude was still an impossibility at sea and, for the most part, throughout the sixteenth century the world was being discovered by sailors and explorers who did not know how to plot their discoveries on a chart. Mercator’s map perpetrated one outlandish mistake, as John Noble Wilford puts it–the Greek concept of a great southern continent, Terra Australis, which covered the pole and extended north as far as South America and South Africa.55
None of this was made any easier by the fact that, once at sea, time-keeping was difficult and troublesome. Ships generally operated a two-watch system, each of four hours. The passage of time was measured by sandglasses, turned every half-hour and marked by a chant sung by the boy of the watch. (Made chiefly in Venice, these sandglasses were very fragile and numerous spares were carried–Magellan’s ship had eighteen of them, just in case.) Noon was established by means of a compass card which produced a shadow that shortened, and then lengthened.56
Steering presented a problem, at least until the eighteenth century. There was a long tiller, mortised to the head of the rudder. The helmsman could usually not see where the ship was going and the course was called out to him by the officer of the watch. Rudders were of little use in a following sea, or even one that was beam-on, and in storms as many as fourteen men might be needed to hold the tiller steady. In the seventeenth century a whipstaff was introduced–this was a long lever working with a fulcrum set in the quarter-deck, and attached to the tiller by a ring. This allowed the helmsman to watch the sails and gave him some extra leverage, but again it was less than perfect in rough weather. Eventually a yoke was fitted to the head of the rudder and lines were led through a series of blocks to a horizontal d
rum on the quarter-deck, which could be rotated by a wheel. But the ship’s wheel did not appear until the eighteenth century.57
In addition to the compass (first used in Europe, by tradition, at Amalfi) there was the lead and line. By using a deep-sea lead and line the seaman could get an early indication of land–it was known that the sea descended to a depth of about 100 fathoms (600 feet) off Europe, then dropped precipitously to much, much deeper levels. Seamen learned that, off Portugal for instance, the continental shelf extended for about twenty miles, while further north, off Britain say, it extended for about a hundred miles. The lead weighed about fourteen pounds and was attached to a 200-fathom line, marked at twenty, then every ten, fathoms with knots indicating the marks. Off a familiar coast, soundings also aided position–seamen learned to remember patterns of the sea bottom. The lead was sometimes hollow and the detritus picked up also helped knowledgeable captains work out where they were.58 Other aids included the Compasso da Navigare, a comprehensive pilot book, covering the whole of the Mediterranean and the Black Sea, which had been compiled by the late thirteenth century. These types of book came into use in the north much later, where they were known as routiers or, in English, ‘rutters’. By the sixteenth century they gave detailed records of soundings.59
As ships ventured into the open sea, pilotage was replaced by navigation proper and one of the early problems here was that there was no way of measuring speed. The earliest method was a piece of wood tied to a rope that was knotted at intervals. When the ‘log’ was released the speed at which the knots ran out over the stern of the ship was timed with a sandglass. This was not very accurate and many sailors–Columbus included–regularly overestimated their speed. Calculation was not made any easier by ignorance of ocean currents but there were tables in place, from the late thirteenth century, which enabled navigators to work out how their position was affected when they tacked before the wind. Rudimentary knowledge of speed helped navigation by dead reckoning but the longer an ocean voyage went on, without knowledge of currents and tides, the greater the inaccuracies that could be expected. The only alternative was navigation by the heavens. The most prominent feature in the night sky was the Pole Star, whose height above the horizon grew less the further south one sailed. This is where the quadrant came in, to provide a reading of latitude. In Columbus’ lifetime, a degree of latitude was reckoned to be 1623 leagues (roughly fifty miles), a considerable error, traceable to Ptolemy. After about 9° N the Pole Star was lost sight of altogether but other stars, whose angular distance from the Pole Star was known, could then be used. The disappearance of the Pole Star of course confirmed (for those who didn’t accept other evidence) that the earth was round.
