owards the east, close upon the horizon line. When we
left in the morning at 7.30, we had _chapada_ and _campos_ on the right
bank and forest on the other side. We had gone some 81/2 kil. from our camp
when we came to a hill range, 75 ft. high, on the right bank, encircling
the river with its thickly wooded slopes. There was a tributary 25 m.
wide, a most beautiful stream, on the right bank. It came from 70 deg. b.m.
Its water was deliciously clear. Where it entered the Arinos it had
deposited a bank of crystals and marble pebbles--yellow, red, and
white--which in the dazzling sun shone with great brilliancy at the
bottom of the river. Numberless rubber trees were to be seen at that spot
on the banks of the Arinos, and also on those of this new important
tributary.

Two kilometres farther, where the Arinos was 280 m. wide, it looked just
like a big lake of stagnant water. The country was quite open on the left
side, first _chapada_, then _campos_.

By 9.30 a.m. we had a most wonderful display of clouds and radiations of
what looked like so many mares' tales from the W.S.W. The river at that
point flowed for 1 kil. in a direction due south. We came to a basin 300
m. across with a spit of white sand on the north-west side. In this basin
was an island--Nattali Island--200 m. long, 20 m. wide, 10 ft. above
water, with a fine beach of sand and gravel on the south side. Gravel
mounds were innumerable in the centre of this stream.

After we had gone some 8 kil. farther down my men shot an _ariranha_.
They had a belief that these _ariranhas_ would easily kill a man in the
water. As we have already seen, they certainly had a great craving for
blood and were always brave in attacking. My men called them "water
leopards." In fact, the head of the _ariranha_ was not unlike the head of
a cat or a leopard. Although shot through the body two or three times,
the _ariranha_ actually came thrice to the attack of the canoe--so that
my men were able to seize it by the tail and pull it inside the canoe
while it was in a dying condition.

Sixteen kilometres farther down we came to another beautiful tributary
with delightfully clear water, 6 m. wide where it met the Arinos. One
hundred metres lower down another little tributary, only 4 m. wide, also
on the right bank, joined our stream. The first tributary seemed to come
from the north-east. At the mouth of this tributary was a spot which
would have made a lovely halting place, but as it w