NAVIGATION

Navigation is then applied, with equal propriety, to the arrangement of the sails, according to the state of the wind and to the directing and measuring a ship's course by the laws of geometry; or it may comprehend both, being then considered as the theory and practice thereof.

Since every sea-officer is presumed to be furnished with books of navigation, in which that science is copiously described, it would be superfluous to enter into a particular detail of it in this place. As it would also be a fruitless talk to those who are entirely ignorant of the rules of trigonometry, and those who are versed in that science generally understand the principles of navigation already, it appears not to come within the limits of our design. It suffices to fay, that the course of a ship, and the distance she has run thereon, are measured by the angles and sides of a right-angled plain triangle, in which the hypothenuse is converted into the distance; the perpendicular, into the difference of latitude; the base, into the departure from the meridian; the angle, formed by the perpendicular and hypothenuse, into the course; and the opposite angle, contained between the hypothenuse and base, into its complement of the course.

The course of the ship is determined by the compass; and the log-line, or a solar observation, ascertains the distance. Hence the hypothenuse and angles are given, to find the base and perpendicular: a problem well known in trigonometry.

That part of navigation, which regards the piloting or conducting a ship along the sea-coast, can only be acquired by a thorough knowledge of that particular coast, after repeated voyages. The most necessary articles thereof are already described in the article COASTING: it issufficient to observe, that the bearings and distances from various parts of the shore are generally ascertained in the night, either by light-houses, or by the different depths of the water, and the various sorts of ground at the bottom; as shells of different sizes and colours, sand, gravel, clay, stones, ooze, or shingle. In the day the ship's place is known by the appearance of the land, which is set by the compass, whilst the distance is estimated by the master or pilot.

Reference Works