64 THE POORNESS OF OUR [CniP. X. 



the few who believe that our present metamorphic 

 scliists 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 

 extent. 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. Ad- 

 mitting 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 

 testimony of travellers, the granitic area is very large : 

 thus. Von Eschwege gives a detailed section of these 

 rocks, stretching from Kio de Janeiro for 260 geo- 

 graphical 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 geograpliical 

 miles, were examined by me, and they all belonged to 

 this class. Inland, along the whole northern bank of 

 the Plata I saw, besides modern tertiary beds, only one 



