13. As soon as the reputation of this instrument had become well established, navigation assumed a bolder character; and the capacity of vessels having been enlarged to meet this adventurous spirit, oars were laid aside as inapplicable, and sails alone were relied upon, as means of propulsion.
14. Navigation, in the early days of its revival, was indebted to the Portuguese for many valuable improvements. To them, also, is the world under obligation for many splendid discoveries, among which was that of a passage by sea to India. This long-desired discovery was made in 1497, by Vasco de Gama, who had been sent out for the purpose by Emanuel, king of Portugal.
15. Five years before Vasco de Gama had found his way to India, by the way of the Cape of Good Hope, Columbus made his discovery of the New World. This great man had conceived or adopted the idea, that the form of our earth was spherical, in opposition to the generally received opinion, that it was an extended plane; and learning that India stretched to an unknown distance eastward, he supposed, that, by sailing in an opposite direction, the navigator would meet with its eastern extremity.
16. Pursuing this idea, he applied successively to the governments of several states and kingdoms for patronage to enable him to test its correctness; and having, at length, succeeded in obtaining three small vessels, with the necessary equipments, from Ferdinand and Isabella, sovereigns of Arragon and Castile, he proceeded on his proposed voyage, which resulted in the discovery of the American continent.
17. These two great discoveries gave another powerful impulse to navigation; and inventions and improvements multiplied in rapid succession. The learned and ingenious, who at different times have turned their attention to the subject of navigation, have supplied the mariner with various means, by which he can direct his course on the deep with accuracy and certainty.
18. The instruments now employed in navigation, are the mariner's compass, the azimuth compass, the quadrant, the sextant, the chronometer, the half minute-glass, the log, and the sounding-line. In addition to these, the general navigator needs accurate maps and charts, lists of the latitude and longitude of every part of the world, the time of high water at every port, and a book of navigation, containing tables, to aid him in performing various calculations with facility; and, with a view to calculate the longitude by observation, he should be furnished with the Nautical Almanac, containing the places and declinations of the fixed stars and planets, and especially the distances of the moon from the sun and other heavenly bodies.