Proceedings of the British Association. 571 



parably greater change in the physical geography of North America, 

 and perhaps of the globe, seems to have occurred at the close of the 

 carboniferous epoch than at any previous or subsequent period ; and 

 they consider these changes, and the effect produced by them on the 

 organic world, as affording some of the highest subjects of geological 

 investigation. 



Mr. Murchison confirmed the views given by the authors of the 

 paper, of the great break in the series of geological deposits which 

 occurs between the Palseozoic rocks and later deposits ; the coincidence 

 in the direction of some great chains in Europe and America, belong- 

 ing to the same geological period, was very striking. He was not 

 prepared to give any opinion upon Prof. Rogers's undulatory theory. — 

 Sir H. T. De la Beche described the general character of anticlinal 

 and synclinal lines, and stated, that whilst contortions of the strata 

 sometimes assumed the character of mountain chains, at other times 

 they occupied large tracts of low ground, as in the comparatively flat 

 country of South Wales. He then made some observations on the 

 space occupied by masses of rock over certain areas ; the older rocks 

 of England, if flattened, would occupy a much greater space than at 

 present ; and the area of the x\lps and Jura would be greatly extended 

 if all their contortions were spread out. The phenomena described in 

 the Appalachian chain, so far as small differences in the direction of 

 the anticlinals were concerned, did not at all affect the brilliant theory 

 proposed by M. Elie de Beaumont; the object of the geologist was 

 to trace the correspondence in the direction of the great lines of eleva- 

 tion, and in this broad view the N.E. and S.W. direction of great part 

 of the European rocks agreed remarkably with the direction of the 

 Appalachian chain. He did not consider the pulsation of molten 

 matter, as described by the authors of the paper, necessary to account 

 for the flexures so very numerous in the strata of mountainous districts, 

 but not confined to them, and in many instances unaccompanied by 

 the intrusion of igneous rocks. The only force necessary for the pro- 

 duction of such flexures and contortions was, the tangential or lateral 

 pressure, in order to compress the strata into a smaller space. Con- 

 tortions were formerly accounted for by a supposed secular diminution 

 in the volume of the earth; the crust was compelled to accommodate 

 itself to the diminished surface arising from the contraction of the mass. 

 But it was to be remembered, that these contortions were not common 

 to all the world : in Russia, the strata presented one even bend over a 

 wide area. Our knowledge of America, and much of the rest of the 

 world, was imperfect ; and until we were much better acquainted with 



