He says himself, "I was constantly corresponding with learned men, some ecclesiastics and some laymen, some Latin and some Greek, some Jews and some Moors." The astronomer Toscanelli was one of these correspondents.
We must not suppose that the idea of the roundness of the earth was invented by Columbus.

Although there were other theories about its shape, many intelligent men well understood that the earth was a globe, and that the Indies, though they were always reached from Europe by going to the East, must be on the west of Europe also.

There is a very funny story in the travels of Mandeville, in which a traveler is represented as having gone, mostly on foot, through all the countries of Asia, but finally determines to return to Norway, his home.

In his farthest eastern investigation, he hears some people calling their cattle by a peculiar cry, which he had never heard before.

After he returned home, it was necessary for him to take a day's journey westward to look after some cattle he had lost.