74 ON SOME POINTS IN DYNAMICAL GEOLOGY. [VII. 



tion of the nucleus is brought, in the manner which I long 

 since explained, to act upon the great accumulations of sedi- 

 ment, so that they are "crushed together horizontally and 

 swelled up vertically," thus producing not only plications 

 and slaty cleavage, but an amount of vertical extension "fully 

 adequate to account for the upheaval of the greatest mountain- 

 chains " ; the ridges, peaks, gorges, and valleys of mountain- 

 regions being, however, the results of subsequent erosion. This 

 theory of the plications of strata, and their relations both to 

 great accumulations and to a contracting nucleus, is fully set 

 forth in my paper of 1861, already quoted; where I have also 

 insisted upon the results of "the lateral pressure brought to 

 bear upon the strata in an elongated basin (of subsidence) by 

 the contraction of the globe." 



But while admitting that the process here described must 

 cause elevations of the compressed strata, it must be said that 

 it fails to solve the problem of the uplifting of mountain- 

 regions, the strata of which have, in many cases, undergone 

 neither folding nor lateral compression, but are nearly or quite 

 horizontal. Foldings, contortions, and slaty cleavage, though 

 met with in many mountain-regions, are, in fact, accidents 

 which are to be left out of view in considering the origin of 

 mountains. The student of physical geography may learn 

 from the great elevated plateaus of the globe the truth of De 

 Montlosier's statement, that the great mountain-chains of 

 Europe are but the remains of continental elevations which 

 have been cut away by denudation, and that the foldings and 

 inversions to be met with in the structure of mountains are to 

 be looked upon only as local and accidental. (Ante, page 52.) 

 In a similar spirit Jukes remarks that we learn " how complete- 

 ly the present surface of the earth is a sculptured surface carve, I 

 out by denudation, and how little, as a rule, it is effected by 

 the dislocations, upheavals and convolutions of the rocks be- 

 neath it," (Manual of Geology, 3d ed., 449.) In the case of 

 the uplifted palaeozoic basin of eastern North America, as Hall 

 has well shown, the process of elevation was the same for 

 the thicker and corrugated sediments of the eastern portion 



