chap. xv. of the Cordillera. 591 



cretaceo-oolitic strata, so this later subsidence appears 

 to have been complicated by alternate or local elevatory 

 movement — for the vertical trees, buried in the midst 

 of the Uspallata strata, must have grown on dry land, 

 formed by the upheaval of the lower submarine beds. 

 Presently I shall have to recapitulate the facts, showing 

 that at a still later period, namely, at nearly the com- 

 mencement of the old Tertiary deposits of Patagonia and 

 of Chile, the continent stood at nearly its present level, 

 and then for the third time, slowly subsided to the 

 amount of several hundred feet, and was afterwards 

 slowly re-uplifted to its present level. 



The highest peaks of the Cordillera appear to con- 

 sist of active or more commonly dormant volcanos, — 

 such as Tupungato, Maypu, and Aconcagua, which 

 latter stands 23,000 feet above the level of the sea, and 

 many others. The next highest peaks are formed of 

 the gypseous and porphyritic strata, thrown into vertical 

 or highly inclined positions. Besides the elevation thus 

 gained by angular displacements, I infer, without any hesi- 

 tation — from the stratified gravel-fringes which gently 

 slope up the valleys of the Cordillera from the gravel- 

 capped plains at their base, which latter are connected 

 with the plains, still covered with recent shells on the 

 coast — that this great range has been upheaved in mass 

 by a slow movement, to an amount of at least 8,000 

 feet. In the Despoblado Valley, north of Copiapo, the 

 horizontal elevation, judging from the compact, stra- 

 tified tufaceous deposit, capping the distant mountains 

 at corresponding heights, was about 10,000 feet. It is 

 very possible, or rather probable, that this elevation in 

 mass may not have been strictly horizontal, but more 

 energetic under the Cordillera, than towards the coast 

 on either side ; nevertheless, movements of this kind 

 may be conveniently distinguished from those by which 



