416 
PHYSICAL GEOGRAPHY OF 
the rivers Guama and Moju, I have described and en- 
deavoured to explain in my Journal, and need not now 
repeat the account of it. (See page 131.) 
Our knowledge of the courses of most of the tribu- 
taries of the Amazon is very imperfect. The main 
stream is tolerably well laid down in the maps as far as 
regards its general course and the most important bends ; 
the details however are very incorrect. The numerous 
islands and parallel channels, — the great lakes and off- 
sets, — the deep bays, — and the varying widths of the 
stream, are quite unknown. Even the Erench survey ' 
from Para to Obidos, the only one which can lay claim 
to detailed accuracy, gives no idea of the river, because 
only one channel is laid down. I obtained at Santarem a 
manuscript map of the lower part of the river, much 
more correct than any other I have seen. It was, with 
most of my other papers, lost on my voyage home ; but 
I hope to be able to obtain another copy from the same 
party. The Madeira and the Rio Negro are the only ]f 
other branches of the Amazon whose courses are at all 
accurately known, and the maps of them are very defi- 
cient in anything like detail. The other great rivers, 
the Xingu, the Tapajoz, the Purus, Coari, Teffe, Jurua, 
Jutai, Jabari, I^a, Japura, etc., though all inserted in 
our maps, are put in quite by guess, or from the vaguest 
information of the general direction of their course. Be- 
tween the Tocantins and the Madeira, and between the 
Madeira and the Uaycali, there are two tracts of country 
of five hundred thousand square miles each, or each twice 
as large as Prance, and as completely unexplored as the 
interior of Africa. 
