vertical stratification, he finds abundant proofs “that the surface of the globe has been broken up by revolutions and catastrophes.” He also refers to the numerous large blocks of the primitive rocks scattered over the surface of secondary formations, and separated by deep valleys or even by arms of the sea from the peaks or ridges from which they must have been derived, as further proofs of catastrophes; for, it is argued, they must have been either ejected by volcanic eruptions or carried by waters, which, in either case, “must have exceeded in violence anything we can imagine at the present day,” and he therefore concludes that “it is in vain we search among the powers which now act upon the surface of the earth for causes sufficient to produce the revolutions and catastrophes, the traces of which are exhibited in its crust.” He is quite confident that all these changes go on rapidly, periods of catastrophe alternating with periods of repose. The present surface of the earth he holds to be quite recent, and he maintains “that, if anything in geology be established, it is that the surface of our globe has undergone a great and sudden revolution, the date of which cannot be referred to a much earlier period than five or six thousand years ago; that this revolution overwhelmed and caused to disappear the countries which were previously inhabited by man, and the species of animals now best known; that, on the other hand, it laid dry the bottom of the last sea, and formed of it the countries which are at the present day inhabited.” And he further declares that “this event has been sudden, instantaneous, without any gradation; and what is so clearly demonstrated with respect to this last catastrophe is not less so with reference to those which preceded it.”