But were the matter of this globe thrown into a confused, disorganized state, and then put into a quick rotary motion, such as it is known to have, it would throw off from the centre towards the surface, first the heaviest, and next the lighter substances, which is the very order in which they are found to be arranged, in the composition of the earth.
This principle, for it is simply the principle of projectile force, will account for mountains, hills, vallies, plains; and for nearly all the inequalities on the face of the earth. These circumstances depend on the density of substances composing the earth. Substances of the greatest specific gravity are susceptible of the greatest projectile force; and hence we find that mountains are composed of heavy masses of rock, mineral substances, and heavy earths; hills, or the next highest eminences, of earth of the next specific gravity; and plains, or level lands, of lighter substances. Had the earth originally been composed of one uniform substance, sand, for example, of equal fineness and weight, the whole surface of the globe would have presented one uniform level or unbroken plain. But, presuming that it was originally composed of, at least, earths of different densities, the heaviest masses would be first thrown out and raise their heads above the surface of the ocean: thus islands would be formed; and clusters of islands would form continents, rearing their lofty heads into the air; and, if the substances of which they were originally composed, were not as hard as the rocks which we now find on them, the sun and changing temperature of the climates, might convert certain kinds of earth into masses of stone, increasing in specific gravity by petrifaction, and other causes, until the towering peaks of the Alps and Andes assumed their present solid form. One continent having thus emerged, another would naturally be produced simultaneously on the opposite side of the sphere, as an equipoise to the first, to keep equal the earth's motion; until all the heavy substances should be thrown out and united in a compact sphere.
To an observer of the earth the crust every where appears to indicate the emergence of land from water: almost the whole surface of the solid crust is alluvial, and by reasoning and reflecting, we are led to the conclusion, that the solid parts of our globe are nothing more than a crust, and formed into concentric spheres, in accordance with the principles of projectile force. I would ask, what proofs have we, that the sphere we inhabit is solid beyond the degree of thickness necessary to preserve it from injury by its rapid motion round the sun, by its diurnal motion round its own axis, and by its motion round its common centre of gravity with the moon? It has been ascertained with mathematical certainty, that the large planet Jupiter, is more than 1300 times the bulk of the earth, and Saturn independent of his double ring, is about 1000 times the size. If we apply to those prodigious bodies, the reasoning of Newton relative to plastic forms moving variously, there is no just grounds for concluding that they are solid substances to their centres. If they were, their vast weight and remote position would require much more attraction than probably even the sun could furnish, to keep them within their orbits.