Imatges de pàgina
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219. In the wide and pathless ocean, therefore, this instrument proves a certain guide to the mariner and enables him, if he has recorded his past course correctly, to ascertain his exact position at all times on the sea, and to shape his future course accordingly.

220. In the construction of the compass, the magnetic needle is usually placed in a frame, and covered by a glass. Beneath it, in the frame, are marked the 32 points of the compass; that is to say, the whole circle of the horizon is thus divided into 32 parts.

The principal of these are, the four cardinal points, the north, south, east, and west; and these are subdivided into north-east north-west, south-east, and south west, &c. &c.

Obs.-Annexed is the representation of this division; the boxing or repeating of which is, among young sailors, deemed a considerable achievement.

THE MARINER'S COMPASS.

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221. The practice of navigation led, however, to various other discoveries; which now render the mariner's compass not the only guide to the navigator, except, during a series of cloudy weather.

Every child can tell where he is, by looking at objects out of himself; i. e. at the houses, trees, and places, to which he is accustomed.

So it is with sailors: there are certain fixed objects out of the earth, as the sun, moon, planets, and stars; and by the position of these, a skilful sailor with the aid of his instruments can always ascertain his true situation.

222. If it appear by the nautical almanac, that the sun is, on the fifth of June, at London, 61 degrees high at 12 o'clock, and a sailor, by his quadrant, finds it at that time to be 70 degrees high, he concludes that he is nine degrees, or 625 miles, nearer to the vertical place of the sun, or more to the south than London.

223. If it appear by the almanac, that at ten o'clock on the evening of June 5, that the moon comes to a conjunction with the planet Mars, at London, and a sailor find that the conjunction takes place at nine o'clock where he is, he concludes that he is one hour, or 15 degrees, or 1045 miles west of London.

224. The nautical almanac is a work published annually by the British government expressly for the use of navigators. It consists of tables and calculations shewing the positions and motions of the heavenly bodies and their various relations to each other, by means of which, the navigator with

his quadrant, or sextant, and a good watch or time piece, can now ascertain his position in any part of the ocean within a few miles. Several American editions of this most useful work, have been published with important additions and improve ments, for the facility of navigation.

225. So expert are navigators become in our days, that a ship has sailed from Portsmouth to Calcutta in 55 days, and from Batavia to Philadelphia in 78 days, voyages which formerly employed six months; from Portsmouth to Malta in 11 days, formerly two months; to New York in 21 days, formerly two months; and to the West Indies in 21 days, formerly two months.

Drake and Anson were three years in sailing round the world; and this is now frequently performed by merchantmen, in nine or ten months

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Obs. Of all the arts and professions which at any time attract notice, none appear more astonishing and marvellous, than that of navigation, in the state in which it exits at present. This cannot be made more evident, than by taking a retrospective view of the small craft to which navigation owes its origin; and comparing them. to a majestic first-rate ship of war, containing 1000 men, with their provisions, drink, furniture, apparel, and other necessaries for many months, besides 100 pieces of heavy ordnance, and bearing all this vast apparatus, safely to the most distant shores. A man in health consumes, in the space of twenty-four hours, about eight pounds of victuals and drink: consequently, 8000 lb. of provisions are required daily, in such a ship. Let us then suppose her to be fitted out for three months, and we shall find, that she must be laden with 720,000 lb. of provisions. A large forty-two pounder weighs about 6100 lb., if made of brass, and about 5,500 lb. of iron; and generally there are twenty-eight or thirty of these, on board a ship of 100 guns; the weight of which, exclusive of that of their carriages, amounts to 183,000 lb. On the second deck, thirty twenty-four pounders; each of which weighs about 5,100 lb. and therefore altogether, 153,000 lb.; and the weight of the twenty-six or twentyeight twelve-pounders on the lower deck, amounts to about 75,400 lb.; that of the fourteen six pounders on the upper deck, to about 26,000 lb ; and beside that, on the round-tops, there are even three-pounders and swivels. If to this we add, that the complete charge of a forty-two pounder weighs about 64 lbs. and that at least upwards of 100 charges are required for each gun, we shall find this to amount nearly to the same weight as the guns themselves. In addition, also to this, we mus reflect, that every ship must have, by way of providing against exigencies, at least another set of sails, cables, cordage, and tacklings, which altogether amount to a considerable weight: the stores, likewise, consisting of planks, pitch, and tow; the chests belonging to the officers and sailors; the surgeon's stores, and various others articles requisite on a long voyage; with the small-arms,

bayonets, swords, and pistols, make no inconsiderable load; to which we must finally add, the weight of the crew; so that one of these large ships carries, at least, 2,162 tons burden, or 4,324,0001b.; and, at the same time, is steered and governed with as much ease as the smallest boat.

226. There does not, perhaps, exist a more prodigious and wonderful combination of human industry, than is visible on board a first-rate man of war. It appears almost incredible that a vessel so large should be moved and directed in the water with nearly the same rapidity and precision as a small boat; and it is wonderful that human hands could have fabricated and put together such gigantic materials.

227. The immense ropes and cables consist of hemp spun together; the aggregation of timbers lately grew separately in the forests; the ironwork was melted and prepared from the ore: the cannon were cast in the foundery; in short, the whole fabric has been assembled together by man from the raw productions of the earth!

XII. Geography and Astronomy.

228. Geography describes the surface of the earth; the shape and size of the land and seas; the boundaries of empires and states, and their climate and natural productions.

It also teaches the character of the inhabitants; their government, religion, manufactures, and mode of living; and it ought to enable us to avoid their errors, and profit by their experience.

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