THE AMAZON VALLEY. 291
lofty trees, 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, which are much used, to avoid the strong current of the main stream. From the mouth of the river Tapajoz to Coary, on the Solimoes, 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 Madeira, the Purus, and a hundred other smaller streams. All along, from the mouth of the Rio Negro to the mouth of the Iga, 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 Uaupe's, are extensive tracts of land which are annually overflowed.
In the whole country around the mouth of the Amazon, round the great island of Marajo, and about the mouths of the Tocantfns and Xingu, 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 fort- night, subjecting all vegetation to another peculiar set of circumstances. Considerable 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 to devote to it. The area is so vast, and the whole country being covered with forests renders natural sections so comparatively scarce, that the few distant observations one person can make will lead to no definite conclusions.
It is remarkable that I was never able to find any fossil remains whatever, — not even a shell, or a fragment of fossil wood, or anything that could lead to a conjecture as to the state in which the valley existed at any former period. We are thus unable to assign the geological age to which any of the various beds of rock belong.*
My notes, and a fine series of specimens of the rocks of the Rio
- The sandstone rocks of Montealegre have since been ascertained to be
of cretaceous age.
