EARTH (in Astronomy.) One of the pri mary planets, marked by the character (D. According to the Ptolemaic system, it was supposed to be immoveable in the centre of the universe, but according to that of Copernicus it moves from west to east, so as to occasion the succession of day and night, and also an nually round the sun, so as to cause the diffe rent seasons. In the solar system it has its orbit between Mars and Venus, at the dis tance of about 95 millions of miles from the sun, being accompanied by the satellite of the moon, which makes its own revolution round the earth thirteen times, while both make one revolution round the sun. It is 7924 miles in diameter, and its surface contains 150 millions of square miles, in seas inhabited by fishes, and 50 millions of land inhabited by animals and insects; of which America is a third, A& rica and Asia a fourth each, and Europe a sixth. Like the rest of the planets, it has two fold motions, one of 68,000 miles an hour in its annual orbit, and another of 1000 tails in its diurnal rotation ; the two forces being so exactly balanced, that the increased rotative force at the centre diminishes the weight of bodies only a 289th part, as compared with the poles ; the general velocity of the fall being one foot in a quarter of a second. The exterior
surface of the land consists of granitic and pri mary mountains, which slope beneath the ge neral surface, while that surface consists of rocks and strata of later formation, or of mix ed soil and ruins of rocks, which appear to have been displaced by the sea. As man is acquainted with the substance of the earth to the depth only of a mile out of 4000, and as the air, wind, and water, are constantly changing the surface,. general theories, such as those called Volcanic and Platonic, are con temptible, as are all those which relate to the origin and end of such a planet, except the scriptural aceount.