This wild screaming is sometimes accompanied by a peculiar beating sound. It has been described by travellers, and currently believed to be made by the animal beating with his hands upon his breast; but such is not the case. It is very certain that the sound cannot be made by that means. The quality of the sound shows that such cannot be the means employed. I have heard this beating several times, and have paid marked attention to its character. At a great distance it would be difficult to discern the exact quality; but on one occasion, while stopping over-night in a native town, I was aroused from sleep by a gorilla screaming and beating within a few hundred yards. I put 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, but I heard distinctly 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 strokes alternating with great rapidity, and not unlike the manner in which the natives beat a drum, except that the 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 versâ_. 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 this 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 on the highest note or pitch in each case, while the rise and fall of the series of the beaten sounds was 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 the voice ceased, and was not the same in every case. [Illustration: NATIVE CARRIER BOY] I have no doubt that the gorilla beats upon his breast: he has been seen to do so 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 of dead wood or other similar substance.