324 THE POORNESS OF 



few who believe that our present metamorphic schists and 

 phitonic rocks once formed the primordial nucleus of the 

 globe, will admit that these latter rocks have been stripped 

 of their coverina: 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 protecting mantle of rock may not have been very 

 thick. Admitting then that gneiss, mica-schist, granite, 

 diorite, etc., were once necessarially 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 over- 

 lying 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 Switzerlandc South of the Amazon, Boue colors 

 an area composed of rocks of this nature as equal to that 

 of Spain. Prance^ -^taly. part of Germany, 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, stretching from Eio de 

 Janeiro for 260 geographical miles inland in a straight 

 line; and I traveled 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 1,100 geographical 

 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' beautiful map, I have estimated tlie areas by 

 cutting out and weighing the paper, and I find that the 

 metamorphic (excluding 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 tlie metamorphic and granite rocks would be found 

 much more widely extended than they appear to be, if all 



