This novel and serviceable nautical instrument, first made of wood and of a triangular shape, was soon in general use on Portuguese vessels. The astrolabe was improved from time to time. At the beginning of the seventeenth century, when the French seaman, Samuel de Champlain, was exploring the St. Lawrence River and its tributaries, it was a disk of brass, having one of its faces marked with degrees and minutes. A brass rule, called a label, with sight-holes, turning upon a pivot at the centre of the instrument, moved over the marked circumference of the disk. At the zenith part of the instrument there was a small ring by which it could be suspended from the thumb of the person taking an observation. When used the astrolabe was turned to the sun, so that his rays could freely pass through the two sight-holes of the label. In this position the altitude of the sun was indicated on the divided limb of the instrument. Opposite the zenith point was a small eyelet from which a weight could be suspended to keep the instrument from shaking when used.
A representation of the astrolabe found in 1867 in the county of North Renfrew, province of Ontario, Canada, supposed to have been lost by Champlain on his way to Ottawa in 1613. The diameter of the instrument is “five inches and five-eights.” Vide “Champlain’s astrolabe.” By A. J. Russell. Montreal, 1879.
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]
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]