coming from the N.N.W., entered the
Arinos on the right side. The main river had a direction of 305 deg.
b.m.--that is to say, virtually north-west. Great volcanic slabs of rock
and sand-banks were now reached.

The sun was not extraordinarily hot--90 deg. F. at noon. The country on
either side was open--chiefly _chapada_. Beautiful gravel beaches were
now seen, extending half-way across the river, particularly from the left
side.

Another tributary 5 m. wide coming from the N.N.E. was passed on our
right, and beyond this a thick forest with rubber trees was visible,
while _chapada_ continued on the left.

Round a big basin 200 m. in diameter, containing shallow water from 1 to
6 ft. deep, stood a mass of gigantic trees with verdant healthy foliage,
and innumerable abnormally tall _burity_ palms, over 100 ft. high, and
_tucum_ (_Astrocaryum tucuma_)--also of immense size.

Many huge _trinchao_ fish followed our canoe for some time, gazing
curiously at us. They came so impudently near that my men actually hit
them on the head with their paddles.

One more streamlet entered the Arinos on the right side just before we
reached a big basin, 250 m. in diameter, with wonderful gravel beaches in
regular little mounds stretching half-way across the basin. Another
little tributary (on the right side) came next, 7,000 m. farther down
stream. The vegetation was there so dense and so entangled that we could
find nowhere a suitable spot on which to land for our midday halt. About
noon, however, _chapada_ and open country again appeared on the right
bank for a distance of some 2,000 m.

[Illustration: A Formidable Vortex.]

[Illustration: Going down a Violent Rapid in a Narrow Channel.]

There we indulged in a plentiful lunch, the country round being as still
as death. Not a sign could be seen anywhere of a human being; not a
column of smoke indicating the presence of man rose anywhere in the clear
sky. Nowhere did we meet disturbed vegetation; nowhere did we notice a
trail or a passage through the vegetation coming to the water; nowhere
did we meet abandoned camps or any signs whatever that human beings had
ever lived there. There was no animal life of fair size on the surface;
no parrots, no monkeys, no mammals of any kind--only millions of insects,
which made one's life a burden.

It was not so with the river, which was swarming with innocent fish, only
too ready to be killed and supply us with excellent meals. The reason