Helen Wallis, "What Columbus Knew," from History Today, May 1992 (42): 17-23.
Master mariner or dedicated amateur? Helen Wallis examines the state of geographical knowldge when Columbus set sail, and outlines his use of it.

History knows of no man who ever did the like' claimed the epitaph over the tomb of Christopher Columbus in the cathedral at Seville. In the simplest terms his aim was described as 'Buscar el Levante por el Ponente': to seek the East by way of the West. Columbus was not the first to consider the possibility of finding lands across the Atlantic Ocean. His originality lay in the conviction that there was a navigable western route to Asia and his determination to prove the route by sailing it. Unlike the contemporary Portuguese explorers, Bartolomeu Dias and Vasco da Gama, he was not one in a succession of navigators pursuing an agreed and long term aim. He was not a merchant adventurer working with associates such as the armateurs of Dieppe. He was on his own, self taught, with a mystical belief in his destiny.

What Columbus knew and how he came to devise his project are therefore questions of universal interest which have been pondered over by historians through the centuries. The eulogistic and controversial biography of Christopher by his younger son Fernando, the Historie del S.D. Fernando Colombo, was published in an Italian translation from a Spanish original in Venice in 1571, more than thirty years after Fernando's death in 1539. Although a compilation marred by later insertions, this work gives many clues to Columbus' motives.

Other major sources are the contemporary histories, Peter Martyr's De orbe Novo, 1516, Gonzalo Fernandez de Oviedo's Historia General y natural de las Indias, 1535, and Bartolome de Las Casas' Historia de las Indias. Written between 1550 and 1563 but not published until 1875, Las Casas' Historia reveals a close relationship to Fernando's Historie. Seven books which Columbus read and annotated (the postils), now preserved in the Biblioteca Colombiana at Seville, are valuable supplementary evidence. The proceedings of the committees in Spain and Portugal which examined Columbus' proposals also provide a dialogue indispensable to the understanding of his project.

Contemporary ideas of world cosmography which influenced Columbus and his interrogators concerned first the circumference of the globe and the number of miles to a degree, and secondly, the size of the oecumene, the continental landmass of Europe, Africa and Asia, in relation to the whole circumference. Ptolemy and Marinus of Tyre, geographers of the ancient world, were major authorities in Columbus' calculations, as Fernando reports. The recovery of Ptolemy's Geography, written c. 150, was the outstanding cartographic event in the fifteenth-century. When the Geography was printed with maps from 1477 onwards, the world map attributed to Agathodaimon, a contemporary of Ptolemy, became widely known.

Constructed on a framework of latitude and longitude, the map reveals the extent of the known world in relation to the whole. It shows Eurasia extending through 180 degrees of longitude from Cape St Vincent in Portugal in the west, to Catigara in the Far East. This was a great overestimation, as the true distance is only 100 degrees. The error arose from the fact that Ptolemy had taken the circumference of the earth to be a quarter too small. In correcting Ptolemy, Columbus made an even greater error. He preferred the estimate of Marinus, who calculated the oecumene to cover 225 degrees in east-west extent. Columbus then made a further adjustment, pointing out that Marinus and Ptolemy did not know the full extent of eastern lands.

In support of the view that the distance between Western Europe and Asia was small, Columbus turned to the opinion of the Arab geographer Alfraganus (al-Farghani) of the late ninth to tenth century, who gave the length of a degree to be 56-2/3 Italian miles. Columbus took the figure from the D'Ailly's Imago Mundi, written c. 1410. He claimed that he had checked the figure himself. In his annotations he comments on the distance between Lisbon and Guinea, which he had sailed, and on the observations of Bartolomeu Dias, made on the expedition to the Cape of Good Hope in 1488.

The classical authorities cited by Fernando as Columbus' sources in favour of a short western route to Asia included Pliny's Natural History (AD 77), Strabo's Geography (AD 17-23) and Seneca, who wrote in the first book of his Natural Questions (c. AD 50) that with a fair wind a ship could sail from the end of Spain to the Indies in a few days. The quotation for which Seneca is most famous, however, was a favourite prophecy of Columbus, taken from the chorus in the tragedy Medea:

There will come a time in the later years when Ocean shall loosen the bonds by which we have been confined, when an immense land shall be revealed and Tiphys (the pilot of the Argonauts) shall disclose new worlds, and Thule will no longer be the most remote of countries.

Fernando commented, 'Now it is considered certain that this prophecy was fulfilled in the person of the Admiral!'

In extending the eastern Asia of the classical writers Columbus drew upon the travels of Marco Polo and Sir John Mandeville, who had passed 'far beyond the eastern lands described by Ptolemy and Marinus'. Fernando explains:

they do not speak of the Western Sea, but from their description of the East it could be argued that India neighbours on Africa and Spain.

Mandeville, who died in 1372, was the author of one of the most popular travel books. It was compiled from various sources, including the Speculum Mundi of Vincent de Beauvais (who died in 1264), reporting the travels of John de PIano Carpini through the Mongol world of Asia, 1245-47.

Marco Polo was the most important of Columbus' late medieval authorities. Marco's travels (1271-95) to China and back, with a stay in that country of seventeen years, had transformed Europe's ideas of the Orient and had revealed a navigable route around south-east Asia. A total of 138 manuscripts survive, and by 1500 the work had been translated into Latin, Italian, German and Spanish. Columbus had the 1485 abridged Antwerp edition of II Millone (a title alluding to Marco's supposed exaggerations). His many notes in this volume all date from a period when his project was well advanced.

Columbus had learned about Marco Polo from Paolo dal Pozzo Toscanelli, the Florentine physician and cosmographer, to whom he wrote in 1481. Toscanelli was Columbus' most important contemporary authority. In 1474 Afonso V, King of Portugal, had consulted Toscanelli over the shortest route to the lands of spices in Asia. Toscanelli's answering letter was sent to Canon Fernao Martins of Lisbon, a friend who was acting as intermediary. In response to Columbus' enquiry Toscanelli sent a copy of the earlier letter to Martins, and Columbus transcribed this letter on a page of his copy of Piccolomini's Historia (Venice, 1477):

Paul the Physician is delighted to hear that the king (of Portugal) is interested in a shorter way of going by sea to the land of spices... He has made a chart to demonstrate the course. On this chart he has marked divers landfalls that a ship sailing westward from Portugal might make ...

The letter to Martins describes the western route to Asia as follows:

From the city of Lisbon due west there are twenty-six spaces marked on the map, each of which contains two hundred and fifty miles, as far as the very great and noble city of Quinsay (Hangchow) ... And from the island of Antillia, which you call the island of the Seven Cities, to the very noble island of Cipango, there are ten spaces, which make 2,500 miles, that is two hundred and twenty-five leagues. This land is most rich in gold, pearls and precious stones ... But because the way is not known, all these things are hidden and covered, though one can travel thither as with all security.

Toscanelli's chart is lost, and has been reconstructed by various experts. Hermann Wagner's version of 1894 is regarded as one of the most convincing. Wagner postulated that Toscanelli followed the projection of Marinus, with rectilinear meridians and lines of latitude. Ptolemy is the only source of our knowledge of Marinus' projection. It was the only projection described by Ptolemy which could be used by mariners.

Wagner comments that Toscanelli had thus made the first attempt to show on a chart the distance between Europe and Asia in units of distance which sailors could understand and use. Toscanelli's sources were the narative of Marco Polo and the account by the Venetian trader Nicolo de' Conti of travels to the Far East over twenty-five years in the early fifteenth century. Toscanelli's friends and associates included two leading German scholars, the astronomer, Johannes Muller, known as Regiomontanus, and the cosmographer, Nicholas of Cusa, both of whom dedicated books to him. Toscanelli's credentials as a geographical adviser were beyond question, and doubts about the authenticity of his letters are now no longer accepted.

The Genoese world map of 1457, which records the results of Nicolo's travels to Asia has been identified by Sebastiano Crino as probably the work of Toscanelli, but it depicts the sea route from Europe south-eastward to Asia, not the western route which was the subject of the letter and the purpose of the map. It thus could not have been the map sent to Lisbon, with a copy sent later to Columbus.

There is no evidence that Columbus saw the Genoese world map, but the achievements of the Portuguese in their search for the route to India, which the map illustrated, were an important influence on his plans. His experiences as a mariner and his years in Portugal from December 1476 were the initial impetus. Fernando writes:

The Admiral while in Portugal began to speculate that if the Portuguese could sail so far south, it should be possible to sail as far westward, and that it was logical to expect to find land in that direction.

Columbus probably sailed to Mina in Guinea in 1481 under Diogo d'Azambuja, or made a trading voyage in 1482-83 or 1483-84. He was also an experienced Atlantic voyager. A memorial in the Historic gives his first hand account of a voyage beyond Tile (Thule), namely Iceland, in 1477.

Although the evidence for this voyage has been contested, the Paris map, c. 1490, with its detailed depiction of Iceland, appears to support Fernando's statement.

The various clues to Columbus' project listed by Fernando include 'fables and stories' which Columbus heard from persons and sailors who traded with the Azores and Madeira, reporting signs of land from across the Atlantic. Taviani, Columbus' Italian biographer, believes that these were more formative in influencing Columbus' mind than the various books which he turned to later in support of his proposals. Western discovery was in the air some twenty years before Columbus sailed in 1492 but no new evidence has come to light about the 'Unknown Pilot', who is supposed to have given Columbus sailing directions, as reported by Oviedo in 1535.

Chasing theories that Columbus had secret information has been a favourite pursuit of many historian detectives. John Dyson, journalist and adventurer, and Dr Luis Coin, Professor of Navigational History at the University of Cadiz, presented in their BBC Timewatch programme, The Columbus Conspiracy, October 16th, 1991, a new version of the 'hidden agenda' theory. Columbus' negotiations with the authorities in Portugal and Spain depended on a convincing cosmographical presentation. In about 1484, after his return from Guinea he put his proposal for a western voyage to Don Joao II of Portugal. The king referred the matter to his Maritime Committee, the Junta dos Mathematicas. The historian Joao de Barros (1552) reports that the experts 'considered the words of Christavao Colon as vain, simply founded on imagination, or things like that Isle Cypango of Marco Polo...' The proposal was rejected.

Columbus moved to Spain in 1485 to seek support from the Catholic sovereigns, Ferdinand and Isabella. The Junta in its meetings at Salamanca in 1486-87 and again at Santa Fe near Grenada in 1491, debated the question of the proportions of land and sea on the terrestrial sphere. Two divergent theories were current concerning the size of the oecumene, both derived from writings of Aristotle. Roger Bacon (c. 1219-92), citing the De Caelo, argued that the oecumene was large in relation to the terrestrial sphere and that 'those who imagine that the region around the Pillars of Hercules joins the regions of India ... are not suggesting anything incredible'. Between Spain and India there was a 'Mare parvum'. Bacon was accepted by Pierre d'Ailly in his Imago Mundi (Louvain, 1480-83), Columbus' favoured authority.

Many writers, on the contrary, interpreted Aristotle's four elements - earth, water, air and fire - as lying in concentric circles, with water preponderant over earth. Most notable was Paul de Burgos (1350-1435), a converted Jew, who argued that the oecumene could not be greater than half the circumference of the sphere of the water. Spanish cosmographers accepted his ideas.

An Italian observer at the meetings, Alexandro Geraldini, pointed out that the Portuguese voyages into the southern hemisphere had disproved Paul de Burgos' theory. The extension of the African continent far to the south indicated a large-sized oecumene, since the land mass was regarded as circular in shape.

The discouraging experience of the long navigations down the African coast probably explains why Joao II asked Columbus back to Portugal in 1488. Columbus was present in Lisbon in December when Dias arrived home with his report of discovering, naming and rounding the Cape of Good Hope. In a postil to Imago Mundi Columbus refers to Dias taking an observation of latitude by astrolabe and finding himself at 45 degs, a curious error as the Cape lies in 34 deg 50'S. Dias' success in entering the Indian Ocean explains why Joao abandoned further consideration of Columbus' project.

Columbus returned to Spain and had his proposals examined by the Junta of Santa Fe in 1491. There followed a surprising volte-face. Luis de Santagel, keeper of King Ferdinand's privy purse, presented himself to Queen Isabella and pleaded Columbus' cause. Columbus was recalled and his project accepted. With the Portuguese well on the way to India, Spain had nothing to lose by backing an alternative western route.

Two maps of about 1490 are believed to have been associated with Columbus. The Paris map, an anonymous manuscript chart on vellum in the Bibliotheque Nationale, shows the coasts of the Atlantic from Norway to the mouth of the Congo. In the neck of the vellum is drawn a small circular mappa mundi surrounded by nine spheres on the moon and planets. On this mappa mundi Africa is depicted to the Cape of Good Hope and eastern Asia follows Ptolemy. Inscriptions on the map derive mainly from D'Ailly's Imago Mundi and duplicate Columbus' annotations in his own copy. Charles de la Ronciere in 1924 identified the map as by Columbus. Of the various theories put forward today, David Quinn's suggestion that the map was made by Bartolome Colon in association with his visit to England in 1488-89, is the most convincing.

The second map is a large world map c. 1490 by Henricus Martellus, a German cartographer working in Italy in association with the Florentine map engraver and publisher Francesco Rosselli. The map is marked with degrees of latitude and longitude. Although Martellus follows Ptolemy in many features, he corrects him in depicting Portuguese discoveries round Africa and in opening up the closed Indian Ocean. He extends Asia to include China and marks Cipango 20 degrees to the east of China.

The discovery in 1961 of the Martellus map, now in Yale University Library, has solved a puzzle which confounded experts. There is the striking resemblance between the conceptions of Toscanelli and Columbus and the depictions on the globe made by Martin Behaim at Nuremberg in 1492, the earliest extant terrestrial globe. Yet we have no evidence that Columbus and Behaim were collaborators or acquainted. To explain the similarity, authorities such as George E. Nunn conjectured that Columbus and Behaim drew on a common map source. Roberto Almagia speculated that the prototype map was one by Henricus Martellus. The Yale map fits Almagia's concept of the missing map. It appears that Columbus had seen this map, or one very like it, and that Behaim used a copy as one of his main sources.

Columbus' ideas about the measure of the earth and the extent of Eurasia, combined with the evidence of a navigable ocean, were the impulse behind his search for a western route to Asia. Cathay and Cipango (China and Japan) were key elements in the plan. The wealth of these countries was the lure to convince his backers they would gain good returns for their money. The capitulations granted in the titulo of April 3Oth, 1492, by Ferdinand and Isabella, however, were conveniently vague: 'Whereas you, Cristobal Colon, are setting forth ... to discover and acquire certain islands and mainland in the Ocean Sea ...'

Columbus named his project (in retrospect) 'the Enterprise of the Indies'. His idea of the measure of the earth and the distribution of land and sea explains the problem of nomenclature which faced him when he discovered the Lucayan Islands in 1492. What distinguished Asia from Europe on the continental landmass of Eurasia? Where did the Indies end? The term 'Indies' could apply to the whole of eastern Asia. The 'Sea of India' referred generally to the seas of Asia. Yet Columbus' use of the term 'Indies' might imply that the islands and people were already known.

Fernando felt it necessary to justify Columbus' name for his first discoveries as 'the Indies'. Columbus used the name because the islands were in the eastern part of India beyond the Ganges, to which no geography set bounds. 'Indian' was a conveniently unspecific term.

The Lucayan Islands were very different from what Columbus expected. They bore no resemblances to the lands of the Chinese empire as described by Marco Polo. Columbus made much of the nakedness of the Indians, which indicated to him a lack of cultural heritage. On the other hand, Marco Polo had written of the islands of Nocueran (Nicobar), whose naked inhabitants were idolaters. The islands depicted in the eastern margins of Martellus' map could well have fitted into Columbus' picture of islands lacking Chinese culture, but situated in the China Seas.

Columbus was undeterred, and persisted in his plan to reach the Grand Khan. The island of Cuba (also called Juana) raised his hopes. He wrote on October 24th, 1492, 'I believe ... that it is the island of Cipango of which marvellous things are told'. On the second voyage 1493-96, he became convinced that Cuba was part of a mainland, and took sworn statements from his men to that effect, believing it to be the south-east promontory of Asia, the Golden Chersonese.

Columbus' aim on the third voyage (1498-1500), according to Las Casas, was to find the mainland which Joao II of Portugal believed to lie south of the islands, a theory whose source is not known. Columbus discovered Trinidad and the coast of Venezuela. After two weeks of coasting, as Las Casas reports, 'he became conscious that so great a land was not an island but a continent'. Its great river the Orinoco indicated this Columbus called the land an 'Otro Mundo', an Other World. He saw it also as the terrestrial paradise, which D'Ailly had located in the Far East, and reported accordingly to the Sovereigns in his letter from Santo Domingo. He wrote in 1500 that God had made him 'the messenger of the new sky and the new earth' which had been announced in the Apocalypse 'and He showed me where to find it'.

The fourth voyage, 1502-4, was 'El alto viaje' the high voyage. Columbus was now seeking a strait between Cuba, seen as a promontory of China, and the newly discovered continent. From Honduras and Darien he followed the coast of Central America which he identified with Marco Polo's Ciamba (Cochin-China). He was hoping to find a navigable passage into Ptolemy's great gulf, the Sinus Magnus. He believed the Indies were only ten days sailing from the Ganges. The Indians informed him that he was on an isthmus between two seas, but a chain of mountains impeded his progress.

Columbus returned home from the voyage on November 7th, 1504. He died at Valladolid on May 20th, 1506, still believing that he had achieved his aim and discovered Asia in the west.

The first printed map to record the discoveries of Columbus is by Giovanni Matteo Contarini, 1506. It comes from the workshop of Rosselli who had also published the Martellus map of c. 1490. The map reflects Columbus' views at the time of his death.

The Contarini map also records John Cabot's discoveries of 1497-98. They are marked on the east coast of an elongated cape of Asia. A wide sea separates these lands from the Spanish discoveries. Terra de Cuba, Insula Hespanola, and La Dominga are marked between 20 deg N and 30 deg N and described as 'the islands which Master Christopher Columbus discovered at the instance of the Most Serene King of Spain'. To the south lies the continent of the 'Otro Mundo', named 'Terra S. Crucis'. To the west lies the island of 'Zinpangu'. Near the coast of Cathay (China) a legend records Columbus' discovery. It states that he had reached the province called Ciamba (Champa, next to Cochin China). This legend confirms Columbus' belief that he had reached the coasts of south-east Asia on his fourth voyage.

The map by Johann Ruysch of 1507 is similar in general outline to that of Contarini, but lacks the legend off Ciamba. It became much better known than Contarini's map since it was published in the Rome editions of Ptolemy's Geography of 1507 and 1508.

Another map with a close association to Columbus is that of the Turkish admiral Piri Re'is, 1513. Piri Re'is states that his map was compiled from eight world maps, including a map drawn by Columbus in the west. Legends describe in detail Columbus' aims and achievements. The continuation of the coast of South America southward and eastward shows that Piri Re'is was adapting Columbus' discoveries to a Ptolemaic model, but only the Atlantic section now survives. Lope Homem's world map of c. 1519 suggests how the whole map might have looked. It shows the coasts of the New World joined up to the far eastern peninsula of Asia.

The strength of Columbus' belief that he had navigated the western route to Asia pushed into second place his discovery of the 'Otro Mundo'. Paradoxically, this contributed to his loss of the greatest honour, the naming of the New World after him. The interest of the Italians in publishing news of the new discoveries, including those of other explorers, was a major factor in the naming of the continent America after Amerigo Vespucci, the Florentine navigator. Vespucci made three voyages to the New World but claimed to have made four. He wrote letters about his discoveries which were quickly published in various tracts, one of which was Mundus Novus, 1504. This work was the first to reveal the fact that a new continent had been discovered. German versions of the Florence edition became known to the geographer Martin Waldseemuller of St Die, Alsace, who named South America after Vespucci on his world map and globe of 1507. In the Strasburg Ptolemy of 1513 he correctly gave Columbus' name as the discoverer, but through the power of the printed word America had become accepted.

Columbus' misconceptions inspired a voyage which would never have won backers had the truth been known. He became famous for the discovery which he neither anticipated nor intended, the discovery of America.

Hellen Wallis OBE edited The Maps and Text of the Boke of Ideography presented by Jean Rotz to Henry VII now in the British Library (Oxford , The Roxburghe Club, 1981), and has also published on Portuguese exploration, Drake and Raleigh.