The Day the Universe Changed - James Burke [40]
On 11 August 1464, in the Umbrian town of Todi, Nicholas of Kues died on his way to Rome to attend the Pope. Toscanelli attended the funeral rites for his old friend, and there he met the Canon of Lisbon, Fernan Martins de Roriz, the confessor of Afonso, of Portugal. He and Toscanelli added their names as witnesses to Nicholas’s will.
Martins at this time was undoubtedly well informed on the Portuguese sailing expeditions because he was in charge of the navigation committee in permanent session regarding the problems besetting exploration of the African coast. The ships’ captains were facing a crisis. The further down the west coast of Africa they went, the lower the Pole Star dropped towards the northern horizon behind them. South of the Equator they would lose sight of it completely, and with it the ability to navigate their way home.
The new charts broke with Christian tradition too, in displacing Jerusalem from the centre of the earth, as it was depicted in medieval world maps, where Europe and Asia were entirely surrounded by the Great Ocean.
A modern reproduction of what Toscanelli’s map of 1474 may have looked like. Note the critical absence of the American continent. Reports had been received of a land-mass in the Atlantic, perhaps the Azores, here shown as the imagined island of Antilia.
This early map of the New World includes South America, discovered early by Portuguese navigation training ships which had been blown west in the south Atlantic. The presence of a new continent questioned the completeness of revealed truth, since the Bible made no mention of it.
Navigation at the time was principally a matter of finding a destination by taking the angle of altitude of the Pole Star at certain hours, and then ‘running up or down’ the north-south latitude lines. Coming north the navigator would sail until the star was in the right position, then turn east until he came to Lisbon. South of the Equator, the stars were unknown. No altitude tables existed for them. Some other way of navigating had to be found, if the ships were not to lose their way.
The new method took Toscanelli back to his days with Nicholas. If perspective geometry allowed the measurement of an object at a distance, the same might be done with the surface of the earth. The gridding method gave metric coherence. With a regular scaled map to go by, a sailor returning from south of the Equator could sail north by the sun a given number of grid distances, and find his way back by the same method.
As he developed this idea, Toscanelli must have seen its potential application for a greater enterprise about which Afonso’s ambassador had also spoken in Florence some years before. This was the possibility of finding an alternative to the West African route to the Spice Islands. The Portuguese had been undertaking training voyages out into the southern Atlantic, navigating by the sun. Toscanelli remembered that during his conversations with Conti, the traveller had said that he thought there was a great ocean to the east of Japan. Where was its other edge?
Finally, on 25 June 1474, Toscanelli wrote to Martins, in Lisbon:
I am pleased to hear the King is interested in a shorter route than the African one now being attempted.… I enclose a chart showing all the islands from Ireland to India and South to Guinea [Ghana].… the straight lines across the map show the distance East—West… the others show the distance North—South.… if you go West from Lisbon… you get to the fine and noble city of Quinsay [Cathay, China]… and… to Chipango [Japan]… full of gold, pearls and precious stones…
Toscanelli’s chart was based on an assessment of the circumference of the earth using the value of a degree at the Equator as equal to 75 miles. He reckoned that Quinsay was about a third of the circumference from Lisbon, at the same latitude of 40°N. So he divided his chart up