In the Manfroni Palace at Venice is a square room about twenty-five feet high, with a concave roof, in which a person standing in the centre, and stamping gently with his foot on the floor, hears the sound repeated a great many times; but as his position deviates from the centre, the reflected sounds grow fainter, and at a short distance wholly cease. The same phenomenon occurs in the large room of the Library of the Museum at Naples. EXTRAORDINARY FACTS IN ACOUSTICS. An intelligent and very respectable gentleman, named Ebenezer Snell, who is still living, at the age of eighty and upwards, was in a corn-field with a negro on the 17th of June, 1776, in the township of Cummington, Mass., one hundred and twenty-nine miles west of Bunker Hill by the course of the road, and at least one hundred by an air-line. Some time during the day, the negro was lying on the ground, and remarked to Ebenezer that there was war somewhere, for he could distinctly hear the cannonading. Ebenezer put his ear to the ground, and also heard the firing distinctly, and for a considerable time. He remembers the fact, which made a deep impression on his mind, as plainly as though it was yesterday. Over water, or a surface of ice, sound is propagated with remarkable clearness and strength. Dr. Hutton relates that, on a quiet part of the Thames near Chelsea, he could hear a person read distinctly at the distance of one hundred and forty feet, while on the land the same could only be heard at seventy-six. Lieut. Foster, in the third Polar expedition of Capt. Parry, found that he could hold conversation with a man across the harbor of Port Bowen, a distance of six thousand six hundred and ninety-six feet, or about a mile and a quarter. This, however, falls short of what is asserted by Derham and Dr. Young,—viz., that at Gibraltar the human voice has been heard at the distance of ten miles, the distance across the strait. Dr. Hearn, a Swedish physician, relates that he heard guns fired at Stockholm, on the occasion of the death of one of the royal family, in 1685, at the distance of thirty Swedish or one hundred and eighty British miles. The cannonade of a sea-fight between the English and Dutch, in 1672, was heard across England as far as Shrewsbury, and even in Wales, a distance of upwards of two hundred miles from the scene of action. Puzzles.