Extract

1.—A great reform in geological speculation seems now to have become necessary. A very earnest effort was made by geologists, at the end of last century, to bring geology within the region of physical science, to emancipate it from the dictation of authority and from dogmatic hypotheses. The necessity for more time to account for geological phenomena than was then generally supposed to be necessary, became apparent to all who studied with candour and with accuracy the phenomena presented by the surface of the earth. About the end of last century, also, physical astronomers made great steps in the theory of the motions of the heavenly bodies, and, among other remarkable propositions, the very celebrated theorem of the stability of the planetary motions was announced That theorem was taken up somewhat rashly, and supposed to imply more than it really did with reference to the permanence of the solar system. It was probably it which Playfair had in his mind when he wrote that celebrated and often-quoted passage—“How often “these vicissitudes of decay and renovation have been repeated is “not for us to determine; they constitute a series of which, as the “author of this theory has remarked, we neither see the beginning “nor the end; a circumstance that accords well with what is “known concerning other parts of the economy of the world. In “the continuation of the different species of animals and vegetables that inhabit the earth, we discern neither a beginning nor “an end; in the planetary

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