SYSTEM OF UNIVERSAL GEOGRAPHY. BOOK I. Theory of Geography. Of the Earth, considered as a celes tial Body, and in its relations to the other celestial Bodies. Of Latitudes and Longitudes. In exhibiting under one view the actual state of the science of Geography, the statement of general truths ought to precede the detail of particular facts. We shall therefore consider our planet in relation to its dimensions and physical structure, before entering upon the study of the different countries which cover its surface. excluded It belongs to astronomy to exhibit to our view the earth Astronomy balanced by its own weight in the immensity of space, re- from this volving, with all the other planets, around the resplendent treatise. luminary, which distributes to each of these celestial globes its portion of light and heat. It belongs also to astronomy to ascertain the laws which govern the solar system, and to trace the orbits of the different bodies which compose it; of Mercury, lost in the rays of the sun; of Venus and of Mars, in the neighbourhood of our earth, but which are not attended by any moon or satellite; of Vesta, Juno, Ceres, and Pallas, which are so closely connected with each other; and lastly, of Jupiter, Saturn, and Uranus, each BOOK I. Proofs of dity of the earth. surrounded by a magnificent train of satellites, or secondary planets. It is still farther the business of the astronomer, to demonstrate that the magnitude of the sun is 1,384,462 times greater than that of our planet, which in this respect is in like manner surpassed by Jupiter 1,281 times; by Saturn 995 times, and by Uranus, 80 times; while all the other planets are inferior to it.* As geography exclusively is our province, it is sufficient for us to borrow such notions belonging to astronomy, as are necessary for comprehending the terms employed in reference to geographical maps, and for conceiving the truth of the methods used in constructing these representations of our globe. The spherical form of the earth is the fundamental printhe rotun- ciple of all mathematical geography. The proofs of this truth present themselves to the senses. The phenomena of the heavens discover it to us; terrestrial appearances also render it obvious. We shall begin with the latter. Proofs drawn from ter Were we placed in a vast plain of Arabia, or on the surface of the ocean, no mountain would there intercept the restrial ap- objects situate within the range of our vision. Why then pearances. do we not see elevated objects only diminish in apparent magnitude, as they recede from our view, without any portion being hid; as would certainly be the case if we were upon the same horizontal plane with them? Why do towers, vessels, and mountains, when we recede from them, appear to sink below the horizon, commencing with the base? and why, on the contrary, when we approach them, do these objects shew first their summits, and thereafter their middle, and last of all their lower parts? These phenomena, which every one has an opportunity of observing, prove evidently that every apparent plane upon the earth is a curve surface. It is the convexity of this surface which conceals from the eye of the spectator, upon the beach, the See, in the Sequel of this Book, the Synoptical Table of the solar System. Consult Laplace, Exposition du Système du Monde; Biot, Astronomie Phy. sique. ↑ Varenius, General Geography revised by 1. Newton, b. I. sect. ii. chap. 3 Maupertuis, Elements of Geography, chap. 2. But BOOK hull of the vessel of which he sees the masts and sails. I. rived from ances. The objects at which the first observers of the stars aim- Proofs deed in their researches was, without doubt, to find certain celestial guides in the voyages which either curiosity or necessity appearprompted them to undertake. They remarked that the sun, their first guide, occupied, in the celestial hemisphere, a place opposite to certain stars, which every night were constantly visible over their heads, while other stars disappeared and re-appeared alternately. Their attention was particularly attracted by the pole star: they marked this point in the heavens, which, itself alone immovable, appears to serve as a pivot, or, according to the Greek expression, as a pole,* to the apparent motions of the heavenly bodies. They next traced a meridian line, that is, a right line in the direction from the sun at noon to the pole star; and however imperfect this first operation may have been, it was sufficient to mark out to them the four quarters of the world, usually denominated the cardinal points. Now, if they proceeded towards the north, they saw the pole star take a position more elevated in the heavens, with regard to the circle which on all sides bounded their view, and which is named the horizon. Did they go towards the south, this same star appeared to sink, and others, before invisible, appeared successively to rise. It was therefore impossible that the line whose direction they followed, could be a straight line traced upon a horizontal plane; it could *Пoxos, a pivot, from weer, to turn. I. BOOK only be a curve, an arc of a circle, to which corresponded another arc of an imaginary circle in the heavens. But as the same changes of the horizon had every where taken place, it was natural to conclude that the earth had at least a circular form from north to south. Confirmed It was without doubt by some such reasoning that Anaximander, and some other of the ancient philosophers, were led to regard the figure of the earth as cylindrical.* Astronomical observations, by being multiplied, were rendered perfect. The motions of the heavenly bodies were calculated from fixed epochs; and the periodical return of eclipses was determined. It was then easily perceived, that the sun rises sooner to those who dwell more towards the east, and gradually later to others in proportion as they are removed to the west; for if an eclipse of the moon is observed at Paris and at Vienna, and if this eclipse begin when it is ten o'clock at night at Paris, it will be near eleven o'clock at Vienna before its commencement is observed; so that the sun must rise sooner to the inhabitants of Vienna, than to those of Paris. This, however, could not happen unless the surface of the earth were curved from east to west; for were it flat, the sun would begin to illuminate all parts of the face of it at the same instant. Lastly, when by a series of observations, we are fully convinced that the eclipses of the moon are caused by the conical shadow of the globe of the earth, we have a complete confirmation of all the preceding proofs in favour of the rotundity of the earth; and we see at the same time, that the globe of the earth is not subject to any great irregularity; since, in all possible positions, its shadow upon the disk of the moon is found to be terminated by an arc of a circle. The numerous voyages which have been made round by voyage the world, have finally shut the mouths of all those who as a round plane, or a round the world. persisted in regarding the earth hemispherical disk. Navigators, such as Magellan and Arist. de Cœlo, lib. ii. cap. 13. |