512 



searches of comparative geography. The small 

 system of mountains, which we shall call pro- 

 visionally, that of the sources of the Rio Negro and 

 the Uaupes, and the culminant points of which 

 are not probably from 100 to 120 toises high *, 

 appear to extend towards the south to the ba- 

 sin of Rio Yupura, where rocky ridges form the 

 cataracts of the Rio de los Engaiios and the Salto 

 Grande de Yupura (south lat. 0° 40' to north 

 lat. 0° 28'), and the basin of the Upper Gua- 

 viare towards the west. We find in the course 

 of this river, from 60 to 70 leagues west of San 

 Fernando del Atabapo, two walls of rocks that 

 bound the strait (nearly 3° 10' nor. lat. and 73|' 

 long.) where the excursion of father Maniella 

 finishes. That missionary told me, that in going 

 up the Guaviare, he perceived near the strait 

 (Angostura), a chain of mountains bounding 

 the horizon on the south. It is not known 

 whether those mountains traverse the Guaviare 

 more to the west, and join the counter-forts 

 which advance from the eastern Cordillera of 

 New Grenada, between the Rio Umadea and 

 the Rio Ariari, towards the savannahs of San 

 Juan de los Llanos. I doubt much of this 

 communication; if it had taken place, the 

 plains of the Lower Oroonoko would commu- 

 nicate with those of the Amazon only by a very 



* Vol. v, p. 332. 



