The current of the river is a slight one, the drop being not greater than eight inches in a mile. No stream could be more convenient for navigation, since the prevailing wind is southeast, and sailing boats may make a continuous progress to the Peruvian frontier, dropping down again with the current. In our own case the excellent engines of the Esmeralda could disregard the sluggish flow of the stream, and we made as rapid progress as if we were navigating a stagnant lake. For three days we steamed northwestwards up a stream which even here, a thousand miles from its mouth, was still so enormous that from its center the two banks were mere shadows upon the distant skyline. On the fourth day after leaving Manaus we turned into a tributary which at its mouth was little smaller than the main stream. It narrowed rapidly, however, and after two more days’ steaming we reached an Indian village, where the Professor insisted that we should land, and that the Esmeralda