The left bank, through which a streamlet cut its way into the Arinos, was fairly open with chapada. An island, 150 m. wide and 200 m. long—Julia Island—was next seen. It had an extensive beach of gravel at its southern end, and the island itself was covered with dense and very beautiful vegetation. Another streamlet 1 m. wide entered the Arinos opposite the island from the left side. Farther on another streamlet, 3 m. wide at the mouth, and coming from the north, flowed into the main stream on the right side. Three and a half kilometres farther another tributary streamlet, also 3 m. wide, was met on the right. We there saw chapada on both banks as we went along, with merely a thin edge of trees along the river.
Where the river described a graceful elbow, a charming tongue of land, with deliciously green grass upon it, was most refreshing to the eyes. A river 8 m. wide at the mouth was met a little way beyond on the left side. We noticed opposite that place a beautiful spot for making a camp, but it was not a convenient hour for us, and so we went along.
About 1,500 m. farther down a long narrow island (200 m. long, 80 m. wide)—Gemma Island—heavily wooded, was passed and admired. It had the usual gravel spit on its southern or up-stream point, the river in that particular spot flowing due north in a perfectly straight line for 4,000 m. The island stood in the centre of a basin 200 m. broad. There were campos and chapada on the left bank.
We landed on the island, and found most beautifully clean forest, nice and cool in the greenish dim light which penetrated through the dense masses of foliage. Particularly noticeable for their beauty were the handsome large mimosas.
On the right bank of the river was forest with plenty of rubber trees, but occasionally even on that side patches of what the Brazilians call serradão (close forest) were met with.
A hill range 120 ft. high formed a crescent from west to north-west on the left side of the stream. A kilometre and a half farther forest was to be seen on the left side of the river; whereas on the right was chapada and campos, quite open. A picturesque rocky island, 15 m. in diameter, in laminated horizontal and rich brown volcanic rock, rose 3 ft. above the water in the centre of the stream. From that spot for 2 kil. I noticed chapada on the right bank; then after that was beautiful dense forest on both sides, with innumerable vigorous rubber trees.
The river there was 200 m. wide and had shallow water with strong corrideiras over enormous parallel transverse dunes of sand and gravel which formed the bottom. Islets of gravel were exposed, especially near the left bank and in the centre, leaving only a more or less navigable channel near the right bank.
We ran aground many a time along the 500 m. of shallow water, varying from 6 in. to 3 ft. deep. We emerged into a large basin 300 m. wide where eddies of no great strength were formed. On the edge of the beautiful basin we halted for our lunch, and to take the usual astronomical observations at local noon. We were in lat. 12° 26′·5 S.; long. 56° 47′ W.
I do not know if I have ever seen such swarms of bees and butterflies as I saw at that place. They seemed to swoop down upon us in myriads from all sides. Taking the solar observations with the sextant and artificial horizon, I endured positive torture with the hundreds of bees which settled on my forehead, nose and hands; while thousands of mosquitoes and ants stung my legs, arms and face in those spots where it was not possible to wrap myself up with towels.
It will be noticed in most of the photographs which were taken along the river, and some of which illustrate this book, that all my men have their heads wrapped up. This was done as a protection against the tantalizing insects. The temperature was warm; that day, for instance, was 105° F. in the sun and 86° in the shade.