420 
GEOLOGY OF 
whose stems are every year, during six months, from ten 
to forty feet under water. In this flooded forest the 
Indians have paths for their canoes, cutting across from 
one river to another, and much used, to avoid the strong 
current of the main stream. Erom the mouth of the 
river Tapajoz to Coary, on the Solimdes, a canoe can 
pass, without once entering the Amazon : the path lies 
across lakes, and among narrow inland channels, and 
through miles of dense flooded forest, crossing the Ma- 
deira, the Purus, and a hundred other smaller streams. 
All along, from the mouth of the Pio Negro to the 
mouth of the I^a, is an immense extent of gapo, and 
it reaches also far up into the interior ; for even near the 
sources of the Rio Negro, and on the upper waters of 
the Uaupes, are extensive tracts of land which are an- 
nually overflowed. 
In the whole country around the mouth of the Ama- 
zon, round the great island of Marajo, and about the 
mouths of the Tocantins and Xingh, the diurnal and 
semi-monthly tides are most felt, the annual rise and fall 
being almost lost. Here the low lands are overflowed 
at all the spring- tides, or every fortnight, subjecting all 
vegetation to another peculiar set of circumstances. Con- 
siderable tracts of land, still covered with vegetation, 
are so low, that they are flooded at every high water, and 
again vary the conditions of vegetable growth. 
GEOLOGY. 
Fully to elucidate the Geology of the Amazon valley, 
requires much more time and research than I was able 
