3G0 
BASIN OB THB BIO NEGBO. 
of waters is formed by the mountains of the Parime group; 
it first rises a little ou the north-east towards the sources 
of Orinoco (lat. 3^ 45 ?) and the chain of Pacaraina 
(lat. 4° 4' — 4® 12') ; then, during a course of 80 leagues, 
between the portage of the Anoeapra and the banks of the 
Eupunun, it runs very regularly from west to east; and 
tinally beyond the meridian 61° 50', it again deviates towards 
passing between the northern sources of the 
Ivio Suriname, the Maroni, the Oyapoc, and the southern 
sources of Eio Trombetas, Curupatuba, and Paru (lat. 
??)• T'lese 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 Cassiquinre alone lias cut its 
way across the ridge just described. The hydraulic svstem 
of the Ormoco displays the singular phenomenon of a bifur- 
cation where the limit of two basins (those of the Orinoco 
and tlie Eio Negro) crosses the bed of the principal recipient. 
Tn that part ot the basin of the Orinoco which runs in the 
direction of from south to nortli, as well as in that running 
from west to east, the maxima of depression are found at the 
toot of the Sierra Parime, we may even say, on its out- 
line. 
IV.— The basin oe the Eio Negbo and the Amazon 
This IS the central and largest basin of Soutli America. It 
IS exposed to frequent equatorial rains, and the liot 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 ■Pampas of Buenos Ayres or the Eio do la Plata) are 
savainahs or prairies, plains without trees and covered with 
gramina. I his sjinmetric distribution of savannahs bounded 
by impenetrable forests, must be connected with physical 
revolutions which have operated siiiiultaneouslv' over great 
Biufaces. ' “ 
>C^’) Fart of the basin of the Amazon, running from east to 
(West, between 2’ north and 12° south ; 880 leagues in length. 
