WHISPERING PLACES are veldts or galleries in which the sound of words uttered with a low voice is augmented, so RR to become audible at a considerable distance from the speaker.
When the air is agitated by any impulse, as the utterance of a word at some spot, the undulations extend spherically in every direction, end thus give rise to perception' of sound which diminish rapidly in intensity as the distance of the auditor increases; but if the impulse be given at one of the extremities of a tube, it is evident that the undulations will be prevented from spreading laterally, and the whole effect, augmented in consequence of the condensation of the partiolea of air in the tube, will be experienced: in this manner maybe explained the increase of the intensity of sound in a trumpet or a speaking-pipe. [Pisa. ] A like effect takes place in a less degree when sound ascends from the bottom of a deep well, or when words are uttered at one extremity of a long corridor or passage in a building. It is said that if a pin be dropped into the well in Cariabrooke Osstle, in the Isle of Wight, the sound produced when it strikes the water is distinctly heard at the mouth : the well is above 200 feet deep. The sound of words spoken near the surface of any long wall is similarly augmented in the direction of the length of the wall ; the latter, in some measure preventing the undulation from being diffused in the atmosphere. The effect in a corridor is frequently increased when the corridor has bends in its length, or when it is smaller at one extremity than at the other. When the place is in the form of a dome, the undulations of the air, which aro produced by a sound emitted near the concave surface, at any part of the base of the dome, are, by continual deflections from every part of the concave surface, transmitted to a point in the base diametrically opposite to that from whence the aonnd proceeded ; and there the waves are concentrated so as to cause the perception of a sound many times louder than that which was emitted.
The whispering gallery in Gloucester Cathedral, which is described in Birch's ' History of the Royal Society,' vol. i., is a passage leading from one aisle to the opposite, behind the east window of the choir : it is 3 feet wide, and about 66 feet high; its whole length is about 75 feet, and its form on the plan is half an irregular octagon : the walls and ceiling are of freestone, and the latter, which is flat, is unevenly wrought. If two persona are placed, one at each end, near either wall, and one converse' with the other in the lowest whisper, the words are as dis tinctly heard as if the persona were close together. The whispering gallery in St. Paul's Cathedral, London, is that which surrounds the base in the concave surface of the interior dome : here a person speaking in a whisper near the surface of the vault is heard distinctly by a person also near the surface and at the opposite extretnity of a diameter, persons in any other part not being able to hear the sound. WHITE ARSENIC. A popular name for arsenious acid. [Aitsesic. Arsenious Acid.]