ORIGIN OF MO UNTAIN RANGES. 555 



cause of mountains justifies the digression, if such it may be 

 called. 



Inferences from j and 4, Folding and Cleavage. — Still adher- 

 ing closely to observed facts, there are some necessary inferences 

 from folded structure and cleavage. These structures are indis- 

 putable proofs that mountain strata have been subjected to enor- 

 mous lateral pressure at right angles to the trend of the axis, by 

 which the whole mass has been mashed together horizontally. 

 But such horizontal mashing must of necessity produce corre- 

 sponding up-swelling along the line of yielding. In a word, it is 

 evident that mountains have been uplifted largely, at least, if not 

 wholly, by horizontal mashing. The only question that remains 

 is, Is lateral mashing alone sufficient to produce the highest 

 mountains? Let us see. 



The amount of uplift in such cases would depend on two 

 things, viz., the thickness of the strata and the amount of mash- 

 ing. Now, as already shown, mountain sediments are 30,000, 

 40,000 and even 50,000 feet thick. The amount of mashing in 

 many mountains is almost incredible. In the Appalachian it is 

 so extreme that in one place, according to Claypole, ninety-six 

 miles of the original sediments have been crowded into sixteen 

 miles, and the shortening of the whole Appalachian breadth is 

 estimated as eighty-eight miles. 1 In the Alps the shortening is 

 estimated by Heim at seventy-two miles or one-half the original 

 breadth of the sediments. 2 In a word, we may without exaggera- 

 tion say that, in great mountains, the original space is to the 

 folded space as two to one, or even three to one. Now a crush- 

 ing of 30,000 feet of sediments into one-half their original space 

 would double their thickness, which is equivalent to a clear ele- 

 vation of 30,000 feet. But strata are 40,000 and even 50,000 

 feet thick. Evidently then this method alone is sufficient to 

 account for the highest mountains in the world, even allowing 

 for the enormous erosion which they have suffered. 



The same is equally shown by the phenomena of slaty cleav- 



J Amn. Natst. Vol. 19, p. 257. 



2 Heim: Archives des Sciences, Vol. 64, p. 120, 1878. 



