The very difficulty of observation rendered this mode of research full of excitement, and at the same time made my method of work very simple. Against the sky, green, blue, or black feathers all appear black, and the first two days my glasses helped but little. For several minutes I would watch some tiny bird which might have been a yellow warbler had I been three thousand miles farther north. After memorizing personal characters, scrutinizing its flight and method of feeding, striving to fix its individuality, I would secure the bird, and find in all probability that it was a calliste, or tanager of brilliant plumage. Tomorrow, if I were lucky, I might be able to tell off the numbers of this species, to watch them and to know that I was watching them. But recognition would not be by way of the cerulean or topaz or amethystine hues of plumage, but by the slight idiosyncrasies of flirting tail or wing or of general carriage. Day by day, as I came to know better the jungle about me, I began to perceive a phase which did not change. Even when the sun shone most brightly, when the coolness of early morning had not yet passed, the mood of the Amazon jungle remained. It was consistent, this low swampy jungle, in its uniform, somber mystery. In spite of wholesale exaggeration it was the dangers which came to mind. Of all places in the world this was probably fullest of life, both in numbers and diversity. Yet it was death--or the danger of death--which seemed in waiting, always just concealed from view. Beneath my tree I squatted silently. Just overhead the foliage might have been almost northern. The finely cut leaves were like willow, and at one side an oak, unusual but still an oak, reached out a thousand thousand motionless leaves, breaking the glare into innumerable patches. But ahead, the terrible interlacing of vines and thorny ropes, the strangle-hold of serpentine lianas on every available trunk--all this could be only tropic. The ground glistened here and there with a film of black water which revealed the swamp. Everywhere the mold and leaves of a hundred years lay scattered, the last fallen still green. Many feet above, great fans dangled, rayed fronds dry and crackling, fallen from high overhead, and suspended, waiting for the interfering twigs and foliage to die in turn and permit them to seek dissolution in the mold.