The remarkable aptitude displayed by Columbus in forming his conclusions that the Atlantic Ocean was navigable, and that ships might pass across its unexplored expanse to Cathay, was the natural expression of his peculiar passion for geographical knowledge. In a letter written to their Spanish majesties, King Ferdinand and Queen Isabella, in 1501, he says: “I went to sea when quite young, and have continued my sea-faring until now; and this profession makes those who follow it eager to discover the secrets of this globe. It is now forty years that I have been sailing to all those places which are at present visited, and I have dealt and talked with learned people, ecclesiastics as well as laymen, Latins, Greeks, Indians, Moors, and many other people of different nations, and our Lord has favored this inclination, and I have received from him the spirit of understanding. He has made me very skillful in navigation, and to know much in astronomy, in geometry, and mathematics. God has given me the knowledge and the ability to portray the globe, and also to delineate cities, rivers, islands, and ports in their proper situation. During my life I have examined and endeavored to see all books of cosmography, history, and philosophy, and of the other sciences, so that our Lord has sensibly opened my mind in order that I may sail from here to the Indies, and has made me extremely anxious to do it.”[109] Columbus’s irrepressible desire to possess all the information he could acquire respecting the navigable water-ways of the Atlantic also led him to sail over the sea-path to Iceland and to the south coast of Africa, at the equator. In his geographical work, written “to show that all the five zones are habitable,” he says: “‘In February, 1467, I sailed myself a hundred leagues beyond Thule, the northern part of which is seventy degrees distant from the equator, and not sixty-three degrees as some will have it to be; nor does it lie upon the line where Ptolemy’s West begins, but much more to the westward, and to this island, which is as large as England, the English trade, especially those from Bristol.[110] At the time I was there the sea was not frozen, but the tides were so great that in some places it swelled twenty-six fathoms and fell as much.’ The truth is, that the Thule of which Ptolemy speaks lies where he says, and this is called by the moderns Frizeland.” Again he says: “I have followed sea-faring for twenty-three years without being on shore any space of time worth mentioning, and I have seen all the East and all the West, and have been to the North where England is situated, and even to Guinea.” He also says that he went to sea when fourteen years old, and ever after that led a sea-faring life.[111]