64 THE POORNESS OF OUR [Chap. X 



ing the few who believe that our present metamorphic 

 schists and plutonic rocks once formed the primordial 

 nucleus of the globe, will admit that these latter rocks 

 have been stript of their covering to' an enormous ex- 

 tent. For it is scarcely possible that such rocks could 

 have been solidified and crystallized whilst uncovered; 

 but if the metamorphic action occurred at profound 

 depths of the ocean, the former protecting mantle of 

 rock may not have been very thick. Admitting then 

 that gneiss, mica-schist, granite, diorite, &c., were 

 once necessarily covered up, how can we account for 

 the naked and extensive areas of such rocks in many 

 parts of the world, except on the belief that they have 

 subsequently been completely denuded of all overlying 

 strata? That such extensive areas do exist cannot be 

 doubted: the granitic region of Parime is described by 

 Humboldt as being at least nineteen times as large as 

 Switzerland. South of the Amazon, Boue colours an 

 area composed of rocks of this nature as equal to that 

 of Spain, France, Italy, part of Germany, and the 

 British Islands, all conjoined. This region has not 

 been carefully explored, but from the concurrent testi- 

 mony of travellers, the granitic area is very large: thus. 

 Von Eschwege gives a detailed section of these rocks, 

 stretching from Eio de Janeiro for 260 geographical 

 miles inland in a straight line; and I travelled for 150 

 miles in another direction, and saw nothing but granitic 

 rocks. Numerous specimens, collected along the 

 whole coast from near Eio Janeiro to the mouth of the 

 Plata, a distance of 1100 geographical miles, were ex- 

 amined by me, and they all belonged to this class. In- 

 land, along the whole northern bank of the Plata I 

 saw, besides modern tertiary beds, only one small patch 



