3GO BASIN Or THE BIO NEGRO. 



of waters is formed by the mountains of the Parime group ; 

 it first rises a little on the north-east towards the sources 

 of the Orinoco (lat. 3 45' ?) and the chain of Facarnina 

 (lat. 4 4' 4 12') ; then, during a course of 80 leagues, 

 between the portage of the Anocapra and the banks of the 

 Rupunuri, it runs very regularly from west to east; and 

 finally, beyond the meridian 61 50', it again deviates towards 

 \ower latitudes, passing between the northern sources of the 

 .Rio Suriname, the Maroni, the Oyapoc, and the southern 

 sources of liio Trombetas, Curupatuba, and Faru (lat. 

 2 1 50'). These facts suffice to prove that this first line 

 of partition of the waters of South America (that of the 

 northern hemisphere) traverses the whole continent between 

 the parallels of 2 and 4. The Cassiquiare alone has cut its 

 way across the ridge just described. The hydraulic system 

 of the Orinoco displays the singular phenomenon of a bifur- 

 cation where the limit of two basins (those of the Orinoco 

 and the Bio Negro) crosses the bed of the principal recipient. 

 In that part of the basin of the Orinoco which runs in the 

 direction of from south to north, as well as in that runniDg 

 from west to east, the maxima of depression are found at the 

 foot of the Sierra Farime, we may even say, on its out- 

 line. 



IV. THE BASIN or THE EIO NEGEO AND THE AMAZON 

 This is the central and largest basin of South America. It 

 is exposed to frequent equatorial rains, and the hot and humid 

 climate developes a force of vegetation to which nothing in 

 the two continents can be compared. The central basin, 

 bounded on the north by the Parime group, and on the south 

 by the mountains of Brazil, is entirely covered by thick 

 forests, while the two basins at the extremities of the conti- 

 nent (the Llanos of Venezuela and the Lower Orinoco, and 

 the p ampas of Buenos Ayres or the Rio de la Plata) are 

 savai /iahs or prairies, plains without trees and covered with 

 gramina. This symmetric distribution of savannahs bounded 

 by impenetrable forests, must be connected with physical 

 revolutions which have operated simultaneously over great 

 surfaces. 



(a.) Part of the lasin of the Amazon, running from east to 

 teest, between 2 north and 12 south ; 880 leagues in length. 



