304 THE POORNESS OF 



beds of considerable horizontal extent have rarely been codU 

 pletely destroyed. But all geologists, excepting 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 stripped 

 of their covering to an enormous extent. For it is scarcely 

 possible that such rocks could have been solidified and 

 crystallized while uncovered ; but if the metamorphic action 

 occurred at profound depths of the ocean, the former protect- 

 ing mantle of rock may not have been very thick. Admit- 

 ting then that gneiss, mica-schist, granite, diorite, etc., were 

 once necessarily covered up, how can we account for the 

 naked and extensive areas of such rocks in any 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 colors an area composed of rocks of this 

 nature as equal to that of Spain, France, Italy, part of Ger- 

 many, and the British Islands, all conjoined. This region 

 has not been carefully explored, but from the concurrent 

 testimony of travelers, the granitic area is very large : thus 

 Von Eschwege gives a detailed section of these rocks, stretch- 

 ing from Rio 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 Rio 

 Janeiro to the mouth of the Plata, a distance of 1,100 geo- 

 graphical 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 small 

 patch of slightly metamorphosed rock, which alone could have 

 formed a part of the original capping of the granitic series 

 Turning to a well-known region, namely, to the United 

 States and Canada, as shown in Professor H. D. Rogers's 

 beautiful map, I have estimated the areas by cutting out and 

 weighing the paper, and I find that the metamorphic (exclud- 

 ing the " semi-metamorphic") and granite rocks exceed, in the 

 proportion of 19 to 12.5, the whole of the newer Palaeozoic 

 formations. In many regions the metamorphic and granite 

 rocks would be found much more widely extended than they 

 appear to be, if all the sedimentary beds were removed which 

 rest unconformably on them, and which could not have 



