559 



way across the ridge we have just described, 

 The hydraulic system of the Oroonoko dis~ 

 plays the singular phenomenon of a bifurca- 

 tion where the limit of two basins (of the 

 Oroonoko and the Rio Negro) traverses the 

 bed of the principal recipient. In that part 

 of the basin of the Oroonoko which lies 

 from south to north, as well as in that lying 

 from west to east, the maxima of the depres- 

 sion are found at the foot of the Sierra Pa- 

 rime, we may even say on its outline. 



L The Basin op the Rio Negro and the Ama- 

 zon. This is the central and largest basin of 

 South America. It is exposed to frequent 

 equatorial rains, and the hot and humid cli- 

 mate developes a force of vegetation to 

 which nothing in the two continents can be 

 compared. The central basin, bounded on 

 the north by the groupe of Parime, and on 

 the south by the mountains of Brazil, is al- 

 most entirely covered by thick forests, while 

 the two basins placed at the two extremities 

 of the continent (the Llanos of Venezuela 

 and the Lower Oroonoko, and the Pampas 

 of Buenos Ayres or the Rio de la Plata) are 

 savannahs or prairies, plains destitute of 

 trees and covered with grain i no, This sy- 

 metric distribution of savannahs bounded by 

 impenetrable forests, must be connected with 



