A stream 5 m. wide at the mouth, coming from the N.N.W., entered the Arinos on the right side. The main river had a direction of 305° 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° 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 trinchão 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.
A Formidable Vortex.
