81 XII. The Art of Navigation. 224. That art must be allowed to be curious and extraordinary, which enables men to conduct great ships with precision, across vast seas many thousand miles wide, in which they often sail for weeks together without seeing any land. 225. Anciently, and indeed till within the last 400 years, no ship ventured out of sight of land. If the mariners lost sight of the land, they gave themselves up, and it would be merely accidental if they ever regained the same shore: such were the disadvantages of Phoenician, Carthaginian, Roman, and Grecian commerce. 226. In the 13th century, it was discovered, by mere chance, that if a certain part of the ore of iron was suspended on a point, and allowed to turn itself at pleasure, it would always point to the north part of the world. Hence, if a seaman took with him to sea one of these loadstones, he was enabled to tell the north, and keep a journal of his course. When from the bosom of the mine, "My bark," she said, "this gem shall guide "While as my daring sons explore "The rude, inhospitable shore, "Mid desert sands and ruthless skies, "New seats of industry shl rise, And culture wide extend his genial reign, "Free as the ambient gale, and boundless as the main." PYE. 227. As the loadstone enabled him to keep an account of the course of his voyage out, so it was not difficult to retrace the same course back, by referring to his journal. If a man in the dark go 50 steps to the right, 20 straight on, and 30 to the left; he will easily return to the place whence he set out, if he takes 30 steps to the right, 20 straight on, and 50 to the left. 228. In the wide and pathless ocean, the loadstone then, by constantly pointing northward, proves a certain guide, and enables the mariner, if he has recorded his past course, to ascertain his exact position on the sea, and to shape his future course accordingly. 229. The loadstone, or magnetic needle, as it is also called, 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 i the boxing or repeating of which is among young sailors, deemed a considerable achievement, 230. The practice of navigation led, how ever, to various other discoveries; which now render the mariner's compass of primary utility, only, during a series of cloudy weather. Every child can always tell where he is, by looking at objects around him; i. e. at the houses, trees, and places, to which he is accustomed. So it is with sailors: there are certain fixed objects around the earth, as the sun, moon, pla neis, and stars; and by the position of these, a skilful sailor can always tell where he is. 231. If it appear by the almanack, that at London, the sun is, on the 5th of June, 61 degrees high at 12 o'clock, and a sailor, by his octant, 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. And thus he determines his latitude. 232. If it appear by an almanac, that at 10 o'clock on the evening of June 6, the hoon comes to a conjunction with the planet Mars, at London, and a sailor find that the conjunc tion takes place at nine o'chuk where he is, he concludes that he is one hour, or 15 degrees, or 1045 longitudinal miles west, Hence he knows the longitude of the place where he is, 233. A Nautical Almanack is published by government, expressly for the use of sailors; and is carried, in many curious particulars, to such a nicety, that by means of his octant, a telescope, and an accurate watch or time-piece, a sailor can now ascertain his position in auy part of the seas within half a mile. 234. So expert are navigators become in our days, that a ship has sailed from. Portsmouth to Calcutta in 55 days, a voyage which for merly 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. 236. Geography describes the surface of the earth; the shape and size of the land and seas, the boundaries of nations, 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 shun their errors, and profit by their experience. Obs.---As there are numerous works adapted for schools on this subject, and the details are very extensive and prolix, it would be trifling with the pages of this work, to dwell tediously on geography. 236. The earth, on which we live, is a round ball or globe, 8,000 miles in diameter, and 25,000 miles round. Its surface is covered with one part of land, and three parts of water, which are inhabited and filled with innumerable living creatures. 237. Öf the internal parts of this immense globe little is known to us. From the surface to the centre is 4,000 miles, yet no mine is a mile. deep. As far as man has penetrated, he has found successive layers or coats of different earths; lying over each other, like the coats of an onion, or the leaves of a book. Obs. In digging wells, various thicknesses of different soils are found in different places, in an order something like the following: three feet of black earth, called ves getable mould, four of gravel, five of gravel and sand, six of clay, three of sea-shells, fifty feet of clay, forty of sand, five of stone, three of marl, &c. &c.; and what is remarkable, every laver is the same thickness as far as it extends, and generamy parallel with the surface of the earth. See my Grammar of Philosophy. 288. The highest mountains detract no more from the roundness of the earth than the ine qualities on the rind of an orange detract from |