THE AMAZON VALLEY, 
409 
are not dyed of that pure golden tint so remarkable 
there. 
On the south of the Amazon there are also some black- 
water streams — the Coary, the Teffe, the Jurua, and 
some others. The inhabitants have taken advantage of 
these, to escape from the plague of the mosquitoes, and 
the towns of Coary and Ega are places of refuge for 
the traveller on the Upper Amazon, those annoying in- 
sects being scarcely ever found on the black waters. 
The causes of the peculiar colour of these rivers are not, 
I think, very obscure ; it appears to me to be produced 
by the solution of decaying leaves, roots, and other ve- 
getable matter. In the virgin forests, in which most 
of these streams have their source, the little brooks 
and rivulets are half choked up with dead leaves and 
rotten branches, giving various brown tinges to the 
water. When these rivulets meet together and accumu- 
late into a river, they of course have a deep brown hue, 
very similar to that of our bog or peat water, if there are 
no other circumstances to modify it. But if the streams 
flow through a district of soft alluvial clay, the colour 
will of course be modified, and the brown completely 
overpowered ; and I think this will account for the ano- 
malies observed, of streams in the same districts being 
of different colours. Those whose sources are pretty 
well known are seen to agree with this view. The Bio 
Negro, the Atabapo, the Isanna, and several other smaller 
rivers, have their sources and their whole course in the 
deep forest ; they flow generally over clean granite 
rocks and beds of sand, and their streams are gentle, 
so as not to wear away the soft parts of their banks. 
