THE AMAZON VALLEY. 
417 
The Rio Negro is one of the most unknown in its 
characteristic features; although, as before stated, its 
general course is laid down with tolerable accuracy. I 
have narrated in my Journal how I was prevented from 
descending on the north side of it, and thus completing 
my survey of its course. 
The most remarkable feature is the enormous width to 
which it spreads, — first, between Barra and the mouth 
of the Rio Branco, and from thence to near St. Isabel, 
In some places, I am convinced, it is between twenty and 
thirty miles wide, and, for a very great distance, fifteen 
to twenty. The sources of the rivers Uaupes, Isanna, 
Xie, Rio Negro, and Guaviare, are very incorrectly laid 
down. The Serra Tunuhy is generally represented as a 
chain of hills cutting off these rivers ; it is however a 
group of isolated granite peaks, about two thousand feet 
high, situated on the north bank of the river Isanna, in 
about 1° north latitude and 70° west longitude. The 
river rises considerably beyond them, in a fiat forest- 
country, and further west than the Rio Negro, for 
there is a path across to the Iniriza, a branch of the 
Guaviare which does not traverse any stream, so that the 
Rio Negro does not there exist. 
My own journey up the Uaupes extended to near 72° 
west longitude. Rive days further, in a small canoe, or 
about a hundred miles, is the Jurupari caxoeira, the last 
fall on the river. Above that, traders have been twelve 
days’ journey on a still, almost currentless river, which, 
by the colour of its water, and the aspect of its vegeta- 
tion, resembles the Upper Amazon. In all this distance, 
which must reach very nearly to the base of the Andes, 
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