On Some Points in Chemical Geology, 425 



rents during the whole palaeozoic period ; and the upper portions 

 of these having been removed by subsequent denudation, we find 

 the inferior members of the series transformed into crystalline 

 stratified rocks. § 



[§ The theory that volcanic mountains have been formed by a sudden 

 local elevation or tumefaction of previously horizontal deposits of lava 

 and other volcanic rocks, in opposition to the view of the older geolo- 

 gists who supposed them to have been built up by the accumulation of 

 successive eruptions, although supported by Humboldt, Von Buch, and 

 Elie de Beaumont, has been from the first opposed by Cordier, Constant 

 Prevost, Scrope and Lyell. (See Scrope, Geol. Journal, vol. xii, p. 326, 

 and vol. xv. p. 500 ; also Lyell, Philos. Trans, part 2, vol. cxlviii, p. 703, 

 for 1858.) In these will we think be found a thorough refutation of 

 the elevation hypothesis and a vindication of the ancient theory. 



This notion of paroxysmal upheaval once admitted for volcanoes was 

 next applied to mountains which, like the Alps and Pyrenees, are com- 

 posed of neptunian strata. Against this view, however, we find De 

 Montlosier in 1832 maintaining that such mountains are to be regarded 

 as the remnants of former continents which have been cut away by de- 

 nudation, and that the inversions and disturbances often met within the 

 structure of mountains are to be regarded only as local accidents. (Bui- 

 Soc. Geol., (1) vol. ii, p. 438, vol. iii, p. 215.) 



Similar views were developed by Prof. James Hall in his address be- 

 fore the American Association for the Advancement of Science, at Mon- 

 treal in August 1857. This address has not been published, but they are 

 reproduced in the first volume of his Report on the Geology of Iowa, 

 p. 41. He there insists upon the conditions which in the ancient seas 

 gave rise to great accumulations of sediment along certain lines, and 

 asserts that to this great thickness of strata, whether horizontal or in- 

 clined, we are to ascribe the mountainous features of North Eastern 

 America as compared with the Mississippi valley. Mountain heights are 

 due to original depositions and subsequent continental elevation, and not 

 to local upneaval or foldings, which on the contrary, give rise to lines 

 of weakness, and favor erosion, so that the lower rocks become exposed in 

 anticlinal valleys, while the intermediate mountains are found to be 

 capped with newer strata. 



In like manner J. P. Lesley asserts that " mountains are but fragments 

 of the upper layers of the earth's crust," lying in synclinals and preserved 

 from the general denudation and translation. (Iron Manufacturer's 

 Guide, 1859, p. 53.] 



