were naturally few, and he had gained a livelihood with ease by the making of maps. His father was a carder of wool at Genoa, and young Christopher, rebelling at the monotony of this trade, commenced his maritime life before he was fifteen years old.

It was doubtless while at Porto Santo that Columbus had thought out his theories, aided by not a little evidence of the material order, such as floating logs and other objects, which had sailed, wind and current borne, from the unknown lands across the Atlantic. Columbus, of course, was not actually the first to feel convinced of the possibility of gaining India by sailing to the West; the theory had been held by Aristotle, Seneca, Strabo, and others. The sole mistake Columbus made in his calculations was concerning the size of the world. He had overestimated the extent of the Continent of Asia, and underestimated the extent of the Atlantic Ocean; he seems to have been convinced that a very few days' sailing to the west of Madeira would bring him to the shores of India. It was this error in calculation that undoubtedly was responsible for many long and agonizing hours spent on the actual voyage.