The campos were particularly neat in that region—merely a few burity and tucum palms flourishing on the edge of the water. In other localities a thick growth of beautiful bamboos interspersed with gigantic palms lined the banks.
Where the river turned due east we came to fairly strong rapids. The water was shallow with mounds of gravel, and we bumped about a great deal. Eventually we all had to get into the water and push the canoe along for greater comfort.
The river next formed a huge basin, 900 m. long and 200 m. wide. A small tributary flowed into the Arinos in the crescent-shaped bank on the right. That bank had a height of 80 ft. On its summit quantities of Siphonia elastica were to be admired. Farther down it was on the left side that the river had high banks, some 60 ft. high.
We went over a charming little corrideira. Strong eddies were encountered on emerging from the rapids. Where the right bank became lower—only 40 ft.—chapada replaced the forest. The left bank was but 1 ft. above the level of the river, and the low country beyond (south) was naturally liable to inundation. For 4,000 m. the left bank was never higher than 4 ft. The right bank also suddenly became very low in that region.
Where the river turned from 290° b.m. to 320° b.m., there was a basin 700 m. broad with low banks. An island—Lydia Island—200 m. in circumference, rose within this basin on the north side and was luxuriantly wooded.
We found that day beautiful beaches of gravel, mostly on the right side. Then strong rapids and corrideiras; below these more clean-looking gravel beaches—this time on the left—were visible, and an extensive island of gravel close to the right bank.
For 8,000 m. the gorgeous stream flowed almost in a direct line northward, with dense forest and a wealthy growth of rubber trees on both sides. Wonderful figueira trees with their spotless white branches embellished the landscape.
On the left a tributary of some size entered the Arinos from the south-east in two arms with an island between; the largest arm was 40 m. wide, the smaller 10 m. Then another stream entered the Arinos on the right side.
We were again confronted by a large basin enclosed on the north by a crescent-shaped wall 100 ft. high, at the foot of which at the level of the river was a quantity of débris of yellow rock. The river at that spot turned sharply from 20° b.m. (N.N.E.) to 290° b.m.—that is to say, almost north-west. The width of the Arinos at this point was from 80 to 100 m.
Towards sunset we came to a beautiful island 200 m. long. We cleared a sufficiently large space in the dense and gorgeous vegetation to make our camp for the night.