ON THE FORMATION OF ROCKS, AND ON FORMATIONS Having now described the different kinds of struc ture which occur in the crust of the earth, we shall next treat of the formation of mountain rocks, and of the revolutions which the earth is alleged to have expe rienced during its formation. But those revolutions are of a different nature from the effects now produced on the surface of the earth ; and therefore the specula tions in regard to them are to be considered more in teresting on account of the facts they bring to light, than from any intrinsic merit they themselves possess. The most ingenious of these speculations respecting the formation of the earth, hitherto proposed, is that of Werner ; and the following statement will, we think, convey to our readers a distinct account of it.
The spheroidal figure of the earth, its crystalline and stratified structures, and its numerous petrifac tions, are proofs of its original fluidity. The fluidity, according to Werner, was aqueous; and he conjectures that the various rocks were originally suspended or dis solved in water, and gradually deposited from it.
In chapter second, when mentioning the effects of ;eater on the surface of the globe, we described several mechanical and chemical depositions which are daily taking place, as it were, under our eye ; and as these present the same kind of structure that occurs in moun tain rocks, Werner infers these also to have been formed by the same agent. As the highest mountains are com posed of rocks, possessing a structure resembling those fossils which have been formed by water, we natu rally conclude, that the ocean must have formerly stood very high over these mountains. Further, as the most elevated mountains are composed of rocks, such as granite, gneiss, mica-slate, clay-slate, and others, which extend around the whole globe, and have been formed during the same period of time, it follows, that the ocean must have formerly covered the whole earth at the same time.—The former great height, and the pre sent low level of the waters of the globe, is so remark able a phenomenon, that it gave rise to many very op posite hypotheses, as soon as it attracted the attention of observers. We shall notice a few of these speculations.
It has been supposed, that the water has suffered a translocation, by a complete alteration of the terres trial poles and equator. This hypothesis, however, is unsupported by fact, as no traces are to be found of so vast a change. The difference between the equato rial and polar diameters, the accumulation of high land around the equator, are proofs that the present poles and equator are the original ones. Even allow ing that such a change had taken place, it is evident that the greatest possible alteration of earth's axis could cause no uncovering of it, as th . water stood
high over the whole globe.
Another opinion was proposed by De Luc, La Me therie, and others ; namely, that the water had retired into caverns, situated towards the centre of the earth. From the description already given of the internal structure of the earth, it is evident that the existence of such caverns is imaginary, and totally irre concileable with the notion of precipitation from a state of solution. Allowing, for a moment, the possi bility of their existence, is it not evident, not only that the water would have rushed into them with such vio lence as to leave the most marked traces of its effects on the surface of the earth, but that the places where the water entered would still be discoverable ? The most probable explanation is that of the gradual diminution of the water from the surface of the earth. It was first obscurely hinted at by Herodotus, Strabo, and other ancient miters. Maillet, French consul at Alexandria, in a work entitled Telliamed, published in 1740, was the first in modern times who directed the attention of philosophers to the theory of the diminu tion of the waters of the globe. This opinion was ea gerly adopted, and keenly supported by Linnaeus, Cel sius, and other Swedish naturalists. They collected many facts, to show that the waters of the Baltic are diminishing ; and the scholars of Linnaeus observed many similar appearances in other countries. Of these, many interesting instances are detailed in the writings of Pallas, Gmelin, Ferber, Niebuhr, Vancouver, Per ron, and others. Even although all these proofs were wanting, it is evident that, if the water remained unal tered in quantity, it would rise and overflow its bound ary, owing to the great quantity of earthy matter which is daily carried into it by rivers and streams. This opinion, as supported by Linnaeus and several others, met with considerable opposition. Many facts were brought forward, to show, that while the land is left by the sea in one place, it is invaded in an equal pro portion in another ; and consequently that there is no diminution of the water. The invasion of the land by the sea is, however, a comparatively rare occurrence ; and besides, these partial elevations of the water de pend on particular circumstances, which can in gene ral be pointed out. Thus, the change in the direction of currents, produced the accumulation of water by winds, the alteration of the shape of coasts, and many other causes, produce alterations in the level of the ocean.