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Show 338 RELATIVE ANTIQUITY [Ch. XXIV, Theory of M. Elie de Beaumont, 1st. He supposes 'that in the history of the earth there have been· Ion{)' periods of comparative repose, during which the deposition ° of sedimentary matter has go~e on in regular continuity, and there have also been short penods ofparoxys· mal violence during w bich that continuity was broken. '2ndly. At each of these periods of violence or" revolution'' in the state of the earth's surface, a great number of mountain· chains have been formed suddenly. '3rdly. All the chains thrown up by a particular revolution have one uniform direction, being parallel to each other within a few degrees of the compass, even wl1cn situated in remote regions ; but the chains thrown up at different periods have, for the most part, different directions. '4thly. Each " revolution," or, as it is sometimes termed, "fri()'htful convulsion," has coincided in date with another geo- o ]ogical phenomenon, namely, ''the passage from one indepen-dent sedimentary formation to another,'' characterized by a considerable difference in ''organic types.'' ' 5thly. There has been a 1·ecurrence of these paroxysmal movements from the remotest geological periods, and they may still be reproduced, and the repose in which we live may hereafter be broken by the sudden upthrow of another system of parallel chains of mountains. '6thly. We may presume that one of these revolutions has occurred within the historical era when the Andes were up· heaved to their present height, for that chain is the best defined and least obliterated feature observable in the present exterior configuration of the globe, and was probably the last elevated. '7thly. The instantaneous upheaving of great mountain masses must cause a violent agitation in the waters of the sea, and the rise of the Andes may, perhaps, have produced that transient deluge which is noticed among the traditions of so wany nations. 'Lastly. '!'he successive revolutions above mentioned cannot Ch. XXIV.J OF M:OUNTAIN-CIIAtNS. 339 be referred .to or~inary volcanic forces, but may depend on the secular rcfngeratwn of the heated interior of our planet*.' It w.i l.l at once b. e seen, that the greater number of the ab ove propositiOns are directly opposed to that theory which we have endeavoured to deduce, partly from the study of the earth's struct.ure, and. partly fro~ the analogy of changes now in progress m the ammate and Inanimate world. Our opini~ns respecting the alternation of periods of general repose and d1sord~r have been explained in former chapters t ; an~ we ha~e pomted out our objections to the }1ypothesis whiCh substitutes paroxysmal violence for the reiterated recurrence of minor convulsions!· The speculation of M. de Beaumont concerning the ' secular refrigeration' of the internal nucleus of the globe, considered as a cause of. the i.nstantaneous rise of mountain-chains, appears to us ~ysterwus m the extreme, and not founded upon any inductiOn from facts; whereas the intermittent action of subterranean volcanic heat is a known cause capable of giving rise to the elevation and subsidence of the earth's crust without interruption to the general repose of the habitable surface. We have shown, in the second volume, that we believe the changes in physical geography, which are unceasingly in progress, to be among the causes which contribute, in the course of ages, to the extermination of certain species of animals and plants; but the influence of these causes is slow and, for the most part, indirect, and has no analogy with those sudden catastrophes which are introduced into the theory now under review. What have appeared to us to be the true causes of the abrupt transitions from one set of strata to another con~ aining d.istinct organic remains, have been explained at l~ngth m the th1rd and fourth chapters of this volume §. • A~n. des Sci. Nat., Septembre, Novembre, et Decembre, 1829. Revue Fran~m.se, No.1~, May, 1830. The last version by M. de B. which I have seen 1s m .the Phil. Mag. and Annals, No. 58, new series, p. 241. t Vol. 1 • PP· ~4 and 88, and Second Edition, pp. 73 and 100 · vol ii p 1 !J6 and S~cond Ed1tion, p. 203. ' · ' · , l Vol. i. P· 79, and Second Edition, p. 90. ~ See particularly from p. 26 top. 34. |