As we went on we were impressed with the amount of work which had been necessary to open up this river for the passage of ballyhoos laden with mine machinery. Six months ago it had been impassable, except for small Indian canoes, and these had often to be dragged ashore and around obstructions. Now the little channel had been opened, and although for the most part completely overhung with interlacing vines and branches, yet our ballyhoo wound in and out around the tacubas with but little hindrance. The cost of opening it had been more than $15,000. Huge tree-trunks had to be sawn through, but even then, the wood of many species having greater specific gravity than water, the trunks would sink to the bottom like stones, offering a greater obstruction than before. Dynamite was then used to clear them from the bed of the stream. In the early afternoon, a beautiful dull-red passion flower on a climbing vine became common, and we found that its fruit was edible and called by the natives Simitú. Although apparently so much at home here, this plant, known as the Water Lemon (_Passiflora laurifolia_), is really an escape from cultivation. The river twisted and turned in every direction and the banks were four to eight feet in height with sloping bars of sand on the inside bends. Palms were rather scarce, their place, in appearance at least, being taken by the tall, slender Congo pump trees with deeply serrated rosettes of leaves. Tree-ferns appeared in ever increasing numbers and stretched their graceful fronds from the banks far out over our heads. During midday, silence filled these river glades, both birds and insects resting quietly in the heat, and the only sound was the regular scraping of the poles against the sides of the ballyhoo. The heat was not oppressive except in the glaring sunshine on the water, but such exposure was rare in these deeply forested recesses. We had had no rain thus far and the temperature of the mornings and evenings was delightfully cool. At night we could scarcely keep warm rolled in a hammock in a thick blanket. Unpleasant insects were entirely absent, and yet we were travelling in the heart of a tropical wilderness, which most of us have pictured as a sizzling, steaming hot-house, teeming with venomous reptiles and stinging bugs of all descriptions. [Illustration: FIG. 118. OUR CAMP ON THE AREMU RIVER.] About three o’clock, the Goldbirds[115] began calling and some other species with a single loud whistle. A Cormorant rose with heavy wing-beats ahead of us, and when we flushed it the second time we shot it. It was the little Guiana Cormorant[47] only twenty-eight inches in length, with eyes of dull green. A deer broke away from the bank at the sound of the shot and dashed off.