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The Earth, the world we inhabit, forms one of the primary planets, which, at various distances, revolve round the sun as a centre, and receive from that resplendent source the blessings of light and warmth. It is a globular or orange-shaped mass of matter, and consists of an indefinite aggregation of earthy, metallic and other substances, chemically and mechanically combined. Vast as the earth appears to the external senses of man, its greatness is only acknowledged by the inferiority of our perceptions. Science has demonstrated the earth to be one of the least among the worlds which traverse the infinity of space, and which are linked together by the force of attraction into a splendid universe. It is only one-fourth the diameter of Uranus, and an eleventh the diameter of Jupiter, and forms therefore a comparatively small portion of the planetary system, and with reference to the stars, only a speck in the vastness of creation.
The earth, according to the calculations of astronomers, is 7,902 miles in mean diameter, and measures about 25,000 miles in circumference. But the diameter, or thickness, is greater at the middle or equatorial line, than in a contrary direction. The cause of this may be here adverted to. The diurnal motion of the earth on its axis, or imaginary poles, causes a greater velocity at the middle than at the extremities of the mass, and the earth, originally in a soft or fused state, has been then bulged out all around. The extent of this bulging is twenty-six miles on the whole thickness, or thirteen miles from the centre to the surface: thus, the globe has a spherical form, and is consequently twenty-six miles greater from one side to another at the equator than betwixt the poles. Such is the nice adjustment of the diurnal motion of the earth on its axis, that, if it were but a little accelerated, the sea would rise and fly off, and if the velocity were somewhat further increased, the whole mass of earth and water would be dispersed in fragments, or, in other words, destroyed : such, indeed, is the perfect balance of all its parts, that to add to, or abstract from, would destroy the whole fabric.
The world, as far as has been ascertained, is a solid mass or body, and consists of two kinds of matter, viz: land and water; the land is composed of rocks, metallic ores, mineral and vegetable soils, and a variety of other substances, to describe which is the province of the geologist; the water, as is well known, is a chemical combination of two gases and the most pervading of all other kinds of matter : as a general mass, it holds in solution various salines; but the water, when pure as it falls from the clouds, is fresh; the one is the water of the sea, while the other is peculiar to lakes and rivers. The greater portion of the earth consists of solid land, but an extensive area of it is covered by a superstratum of water; and therefore, to appearance, the ocean forms the principal portion of the globe. It is so, however, only in appearance, notwithstanding its imposing extent, the water being merely a superficial covering to the subjacent land.