This wild screaming is sometimes accompanied by a peculiar beating sound. It has been vaguely and variously described by travelers, and currently believed to be made by the animal beating with his hands upon his breast; but that is not the fact. The sound cannot be made by that means. The quality of the sound shows that such cannot be the means employed. I have several times heard this beating and have paid marked attention to its character. At a great distance it would be difficult to determine its exact quality. On one occasion, while passing the night in a native town, I was aroused from sleep by a gorilla screaming and beating within a few hundred yards of the village. I drew on my boots, took my rifle, and cautiously crossed the open ground between the village and the forest. This brought me within about two hundred yards of the animal. The moon was faintly shining, but I could not see the beast, and I had no desire to approach nearer at such a time. I distinctly heard every stroke. I believe the sound was made by beating upon a log or piece of dead wood. He was beating with both hands. The alternating strokes were made with great rapidity. The order of the strokes was not unlike that produced by the natives in beating their drums, except that in this instance each hand made the same number of strokes, and the strokes were in a constant series, rising and falling from very soft to very loud, and _vice versa_. A number of these runs followed one another during the time the voice continued. Between the first and second strokes the interval was slightly longer than that between the second and third, and so on through the scale. As the beating increased in loudness the interval shortened in an inverse degree, while in descending the scale the intervals lengthened as the beating softened, and the author of the sound was conscious of the fact. I could trace no relation in time or harmony between the sound of the voice and the beating, except that they began at the same time and ended at the same time. The same series of vocal sounds was repeated each time, beginning on the low note and ending in each case with the note of the highest pitch, while the rise and fall of the series of the beaten sounds were not measured by the duration of the voice. The series each time began with a soft note, but ended at any part of the scale at which it happened to be at the time the voice ceased. The coinciding notes were not the same in every case. No doubt the gorilla sometimes beats upon his breast. He has been seen to do this in captivity, but the sounds described above were not so made. Since the gorilla makes these sounds only at night, it is not probable that any man ever saw him in the act. It does not require a delicate sense of hearing to distinguish a sound made by beating the breast from that made by beating on dead wood or other similar substance.