Noticing in this week's number of the Scientific American an article on Acoustic Telegraphs, I take the liberty of pointing out to you some experiments made by Biot, in one of the pipes of the water works in Puis, the distance being 951 metres (over 3,000 feet). The principal results of these experiments were :— 1st, The time taken in asking a question, and receiving an answer, was 5"'58, during which the sound of the voice had been propagated twice through th1'l length of the pipe or over 6,000 feet. 2nd. The softest whisper which could possibly be articulated,. was distinctly understood, 3rd. Low and acute sounds, as well as loud and soft ones, we re propagated with equal velocity. • The bore of the pipe is not give n, but trom the length ofthe pipe, I suspect that it was probably one of the mains from the distributing reservoir, which, if I recollect right, are not less than twelve inches, perhaps more. The experiments were made, not only with the voice, but by firing pistols, playing the flute, &c. But it was found necessary to make the experiments during the greatest stillness of the night, because in the day time, in such a large city, the atmosphere is filled with such confusion of various sounds, and the ground so much jarred by carriage wheels and other ' causes of constant friction and percussions that metallic pipes of such size, are affected by vibration, and the column of air within was at times so filled with confused I!oises, as to render inaudible even a loud call. This, however, would not be the case in small gut- ta percha pipes.C. S. Quilliard. Rondout, Dec. 11th, 1852.