In the fifteenth century the day’s run of a ship was commonly reckoned by the pilot. In an old nautical work it is said: “In order to know the speed of the ship over the length of the course the pilot must set down in his journal the progress the vessel has made according to hours; and to do this he must know that the greatest distance that a ship advances in an hour is four miles, and with feebler breezes, three or only two.”[102] Time was measured by sand-glasses, or _ampolletas_, as they were called by the Spaniards. Forty-eight changes of these half-hour glasses equalled the space of a day.[103] In 1487 the persistent enterprise of the Portuguese in exploring a commercial route to India along the west and south coasts of Africa was notably signalized by the success attending the expedition commanded by the adventurous seaman, Bartolomeu Dias. The indomitable zeal of this Portuguese mariner enabled him to reach the southern extremity of Africa, where he found a bold promontory to which he gave the name of Cabo Tormentoso, (the Stormy Cape,) commemorative of the adverse winds and bad weather encountered there. King John II., personally appreciating the good fortune attending the explorations of the navigators of Portugal in this direction during the previous seventy years, in which time more than six thousand miles of coast-line had been inspected by them, called the promontory discovered by Dias, Cabo de Boa Esperança (the Cape of Good Hope).[104] CHAPTER III. 1474-1492. The success attending the voyages of the Portuguese along the coast of Africa suggested to Cristoforo Colombo[105] (or Christopher Columbus, as he is more commonly called by those speaking English), the possibility of sailing by a shorter way to India in another direction. Ferdinand Columbus, in his history of the life and achievements of his father,[106] makes no attempt to conceal this fact from publicity. With an apparent intention to give all the information which might be desired concerning the great discoverer’s first thoughts respecting the practicability of reaching Asia by sailing in a westerly direction, he frankly tells what originated them in the mind of the admiral. “As one thing leads to another, and one thought to another, in this way, while the admiral was in Portugal, he began to infer that as the Portuguese sailed so far southward, it was also feasible to steer westward, and that land might likely be found in this direction. In order to be more assured and satisfied in this matter, he began to review the cosmographies which he had read, and to note what astronomical reasons would support this theory.[107] That he might be more enlightened concerning his assumption, he paid attention to what was said by people respecting it, especially by seamen. His diligent investigations soon led him to conclude that there were many lands west of the Canaries and the Cape Verd Islands, and that it was practicable to sail to and discover them.”[108]