Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/52

 48 planet, through long successions of change and of convulsive movements, to a tranquil state of equilibrium; in which it has become the convenient and delightful habitation of man, and of the multitudes of terrestrial creatures that are his fellow tenants of its actual surface.

the summary we have given of the leading phenomena of unstratified and volcanic rocks, we have unavoidably been led into theoretical speculations, and have seen that the most probable explanation of these phenomena is found in the hypothesis of the original fluidity of the entire materials of the earth, caused by the presence of intense heat. From this fluid mass of metals, and metalloid bases of the earths, and alkalies, the first granitic crust appears to have been formed, by oxidation of these bases; and subsequently broken into fragments, disposed at unequal, levels above and below the surface of the first formed seas.

Wherever solid matter rose above the water, it became exposed to destruction by atmospheric agents; by rains, torrents, and inundations; at that time probably acting with intense violence, and washing down and spreading forth, in the form of mud and sand and gravel, upon the bottom of the then existing seas, the materials of primary stratified rocks, which, by subsequent exposure to various degrees of subterranean heat, became converted into beds of gneiss, and mica slate, and hornblende slate, and clay slate. In the