At seven thousand seven hundred feet the forest begins; a collection of half a dozen huts called Incachaca nestles in its inner border, and there we decided to remain for a few weeks. We secured space in a large house belonging to an organization which is engaged in digging a canal along the opposite side of the gorge; when this work is completed the water of the river will be turned into the artificial course and utilized for running dynamos to furnish electricity for the light and street-car service of Cochabamba. A power-house had been constructed at the bottom of the ravine, and the lines for transmitting the current had been strung across the mountains. At Incachaca the river flows through an underground channel; while exploring the forest one day we came suddenly upon the narrow cleft in the mountainside, scarcely a dozen feet across, and with a great deal of effort were finally able to distinguish the roaring white torrent a hundred feet below. The edges of the cleft are so overgrown with ferns that one has no idea of its existence until the very brink is reached. A short distance below, the river emerges from the darkened cavern, and plunging over the face of a precipice, thunders into a pool in a sheer drop of fifty or sixty feet. We found the upper limit of a subtropical fauna at Incachaca. Bird-flocks travelled hurriedly through the trees; they were composed of bright-colored tanagers, finches, and cotingas. Honey-creepers and hummers were plentiful in the flowering shrubs. Queer little ducks called merganettas disported in the pool below the falls, and dippers ran nimbly along the edge of the water. In one of the tall trees near the river we discovered the nest of an eagle. We found it impossible to climb the tree, but a German named Ricardo Marquardt, who was in charge of the workmen along the river, succeeded in reaching the huge mass of sticks seventy feet above the ground, and brought down a beautifully spotted egg. To my companion, Mr. Howarth S. Boyle, who accompanied me on the entire trip, belongs the credit of taking the rarest birds from this locality; they were a pair of white-eared thrushes (_Entomodestes_), which, so far as I can learn, exist in only two other museums. Among the lower growth lived many ant-thrushes (_Grallaria_), whose clear call could be heard at all hours of the day. This is one of the hardest of all birds to collect. The long-legged, tailless songsters never leave the thick growth of ferns and brush, and the only way to secure them is to enter the dense cover, sit quietly, and imitate the clear, ringing call in the hope of attracting the birds; sometimes this requires hours of patient work, and more often than not the effort is futile.