Columbus did not give up his maritime enterprises.  He made voyages to the coast of Guinea and in other directions.

It is said that he was in command of one of the vessels of his relative Colon el Mozo, when, in the Portuguese seas, this admiral, with his squadron, engaged four Venetian galleys returning from Flanders.  A bloody battle followed.  The ship which Christopher Columbus commanded was engaged with a Venetian vessel, to which it set fire.  There was danger of an explosion, and Columbus himself, seeing this danger, flung himself into the sea, seized a floating oar, and thus gained the shore.  He was not far from Lisbon, and from this time made Lisbon his home for many years.(*)

     (*) The critics challenge these dates, but there seems to be
     good foundation for the story.

It seems clear that, from the time when he arrived in Lisbon, for more than twenty years, he was at work trying to interest people in his “great design,” of western discovery.  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.  Finding these cattle, he also heard the same cry of people calling cattle, which he had heard in the extreme East, and now learned, for the first time, that he had gone round the world on foot, to turn and come back by the same route, when he was only a day’s journey from home, Columbus was acquainted with such stories as this, and also had the astronomical knowledge which almost made him know that the world was round, “and, like a ball, goes spinning in the air.”  The difficulty was to persuade other people that, because of this roundness, it would be possible to attain Asia by sailing to the West.

Now all the geographers of repute supposed that there was not nearly so large a distance as there proved to be, in truth, between Europe and Asia.  Thus, in the geography of Ptolemy, which was the standard book at that time, one hundred and thirty-five degrees, a little more than one-third of the earth’s circumference, is given to the space between the extreme eastern part of the Indies and the Canary Islands.  In fact, as we now know, the distance is one hundred and eighty degrees, half the world’s circumference.  Had Columbus believed there was any such immense distance, he would never have undertaken his voyage.