Years before that first great achievement, Christopher Columbus—who had studied at the University of Pavia and had himself taken part in one or more of Prince Henry’s African expeditions, and even ventured to the northwest, probably as far as Iceland—had been converted to the theory that the world was round and that the oceans west of Europe and east of Cathay were the same. As a consequence, he had concluded, the East Indies (as India, China, Japan, and the other countries and islands east of the Indian Ocean were indiscriminately called) _could be reached from Europe by sailing west_. Eighteen years before he was finally enabled to put this theory to the test, he had written Toscanelli, one of the foremost astronomers of the time, asking his opinion as to this possibility. Toscanelli sent him a copy of a letter he had written shortly before to King Alfonso of Portugal on the same subject, in which he said: “I have formerly spoken of a shorter route to the places of spices than you are pursuing by Guinea. Although I am well aware that this can be proved by the spherical shape of the earth, in order to make the point clearer I have decided to exhibit that route by means of a sailing chart, made by my own hands, whereon are laid down your coasts and the islands from which you must begin to shape your course steadily westward, the places at which you are bound to arrive and how far from the pole or equator you ought to keep away.” (Neither in the chart nor in the description was there indication of anything whatever resembling the continents of North and South America.) “From the city of Lisbon as far as the very great and splendid city of Quinsay” (Pekin), he continued, “are twenty-six spaces, each of 250 miles. This space is about a third of the whole sphere. But from the Island of Antilia, which you know, to the very splendid Island of Cipango” (Japan) “there are ten spaces. _So, through the unknown parts of the route, the stretches of sea are not great._” In his letter to Columbus he congratulates him on having undertaken an enterprise— “Fraught with honor, as it must be, and inestimable gain and most lofty fame among all Christian peoples. It will be a voyage to powerful kingdoms” (he prophetically added, though he had never even dreamed of the empires of the Aztecs and the Incas) “and to cities and provinces most wealthy and noble. It will also be advantageous to those kings and princes who are eager to have dealings and make alliances with the Christians of other countries. For these and many other reasons, I do not wonder that you, who are of great courage, and the whole Portuguese nation, which has always had men distinguished in such enterprises, are now inflamed with a desire to make the voyage.”