PLAISS OP THE AMAZOS. 
863 
r.irapiti, wliich lower down takes tlie names of Eio San 
iliguel and Eio Sara. The savannahs of the province nt 
Chiquitos communicate on the north with those of Moxos, 
ftud on the south with tliose of Chaco ; hut a ridge or lino of 
partition of the waters is formed hy the intersection of two 
gently sloping plains. This ridge takes its origin on the 
north of La Plata (CImqnisaca) between the sources of the 
Guapais and the Caehimayo, and it ascends from the parallel 
of 20° to tliat of 15i° south latitude, consequently on the 
north-east, towards tlie isthmus of Villabella. I'rom this 
point, one of the moat important of the whole hydrography 
of America, we may follow the line of the partition of the 
water to the Cordillera of the shore (Serra do Mar). It is 
seen winding (lat. 17°-20°) between the northern sources of 
the Araguay, the MaranhSo or Tocantines, the Eio San Fran- 
cisco, and the southeni sources of the Parana. This second 
line of partition which enters the group of the Brazil moun- 
tains, on the frontier of Capitauia of Goyaz, separates the 
flowings of the basin of the Amazon from tliose of the Eio de 
la Plata, and corresponds, south of the eijuator, with the line 
we have indicated in the northern hemisphere (lat. 2°-4°), 
on the limits of the basins of the Amazon and the Lower 
Orinoco. 
If the plains of the Amazon (taking that denomination in 
the geognostic sense we have given it) are in general distin- 
guished from the Llanos of Venezuela and the Pampas of 
Buenos Ayres, by the extent and thickness of their forests, 
we are the more struck by the continuity of the savannahs in 
that part running from south to north. It would seem as 
though this sea of verdure stretched forth an arm from the 
basin of Buenos Ayres, by the Llanos of Tucuman, Manso, 
Chuco, the Chiquitos, and the Moxos, to the Pampas del 
Sacramento, and the savannahs of Napo, Guaviare, Meta, 
and Apurc. This arm crosses, between 7° and 3° south 
latitude, the basin of the forests of the Amazon ; and the ab- 
sence of trees on so great an extent of territory, together 
with the preponderance which the small monocotyledonous 
plants have acquired, is a phenomenon of the geography of 
plants which belongs perhaps to the action of ancient pelagic 
currents, or other partial revolutions of our planet. 
