3i6 NOTES OF A NATURALIST. 



rainless country, such as Egypt or Peru, we see a 

 slope covered with debris, and are apt to conclude 

 that the rock is being rapidly disintegrated ; but, in 

 truth, what we see is the work of many, perhaps 

 many hundred, centuries, which remains in sitti because 

 there is no agency to remove it. In a land of heavy 

 rainfall the debris is speedily carried to lower levels, 

 and the work of destruction is constantly renewed. 



We have scarcely any observations of rainfall in 

 the mountain districts of Brazil. The only reliable 

 return that I have seen is that of one year's rainfall 

 at Gongo Seco, in Goyaz, which amounted to more 

 than a hundred and thirty inches ; but we may safely 

 conclude that it is everywhere very great. It is also 

 important to note that if, as most geologists now 

 believe, the Atlantic valley has existed since an early 

 period of the earth's history. Eastern Brazil must 

 always have been a land of heavy rainfall. A great 

 mountain range on the eastern side of the continent 

 might have created a desert region in the interior, 

 but would have received in the past as much aqueous 

 precipitation as it does at the present time. 



We have, therefore, to consider what must have 

 been the ancient condition of a region subjected 

 throughout vast periods of geological time to the 

 utmost force of disintegrating agencies applied to a 

 rock very liable to yield to them, and where, without 

 reckoning the large proportion which must have been 

 carried by rivers to the sea, we see such vast deposits 

 of the disintegrated materials formed out of the same 

 matrix. To my mind the conclusion is irresistible 

 that ancient Brazil was one of the greatest mountain 



