324 A JOURNEY IN BRAZIL. 
sky. Cool weather here is usually the result of rain. 
As soon as the sun shows his face the heat is great. But 
yesterday a strong wind was blowing down the Rio Negro ; 
and its usually black, still waters were freshened to blue, 
and their surface broken by white caps. It is a curious 
fact in the history of this river, that, while tributary to 
the Amazons, it also receives branches from it. A little 
above its junction with the Solimoens, the latter sends sev- 
eral small affluents into the Rio Negro, the entrance to which 
we passed yesterday. The contrast between their milky- 
white waters and the clear, dark, amber tint of the main 
river makes them very conspicuous. It would seem that 
this is not a solitary instance of river formation in this 
gigantic fresh-water system ; for Humboldt says, speaking 
of the double communication between the Cassiquiare and 
the Rio Negro, and the great number of branches by which 
the Rio Branco and the Rio Hyapura enter into the Rio 
Negro and the Amazons : " At the confluence of the Hya- 
pura there is a much more extraordinary phenomenon. 
Before this river joins the Amazons, the latter, which is the 
principal recipient, sends off three branches, called Uara- 
napu, Manhama, and Avateparana, to the Hyapura, which 
is but a tributary stream. The Portuguese astronomer, 
Ribeiro, has proved this important fact. The Amazons 
gives waters to the Hyapura itself before it receives that 
tributary stream." So does it also to the Rio Negro. 
The physiognomy of the Rio Negro is peculiar, and very 
different from that of the Amazons or the Solimoens. The 
shores jut out in frequent promontories, which, while they 
form deep bays between, narrow the river from distance 
to distance, and, as we advance towards them, look like 
the entrances to harbors or lakes. Indeed, we have alrea- 
