557 



of almost unknown mountains is placed, that 

 surround the sources of the Rio Negro. (Vol. 

 vi, p. 512). In the basin comprehended be- 

 tween the eastern declivity of the Andes of 

 New Grenada, and the western part of the 

 Sierra Parime, the savannahs, as we have 

 observed above^ stretch far beyond the equa- 

 tor, but their extent does not determine the 

 southern limits of the basin we here examine. 

 The latter are fixed by a ridge that divides 

 the waters between the Oroonoko and the Rio 

 Negro, a tributary stream of the Amazon. 

 The rising of a counterslope almost imper- 

 ceptible to the eye, forms a ridge that seems 

 to join the eastern Cordillera of the Andes to 

 the groupe of Parime *, This ridge runs 

 from Ceja (lat. 1° 45'), or the eastern slope of 

 the Andes of Timana -f, between the sources 

 of the Guayavero and the Rio Caguan J, 

 towards the isthmus that separates the Tua- 

 mini from Pimichin |. In the Llanos, con- 

 sequently, it follows the parallels of 20° 30' 

 and 2°.45 / . It is remarkable, that we find 

 the divortia aquarian more to the west, on 



* Vol. vi, p. 397. 



+ See my Map of Magdalena {Geogr. Atlas, pi. xxiv). 



X The former is a tributary stream of the Guaviare, the 

 latter of Yupura. 



§ Isthmus of Javita, or portage of Pimichin (Vol. v, p. 

 259, 260, 279, Geogr. Atlas, pi. xvi). 



