WHISPERING places, are places where a whisper, or other small noise,..) may be heard from one part to another, to a great distance. They depend on a principle, that the voice, &c. being ap plied to one end of an arch, easily passes by repeated reflections to the other.
Hence sound is conveyed from one side of a whispering gallery to the opposite one, without being perceived by those who stand in the middle. The form of a whispering gallery is that of a segment of a sphere, or the like arched figure ; anti the progress of the sound through it may be illustrated in the following man ner: Let A B C (Plate XVI. Miscel. fig, 12.) represent the segment of a sphere ; and suppose a low voice uttered at A, the vibrations extending themselves every way, some of them will impinge upon the points E, E, &c. ; and thence be reflect ed to the points F, F, &c. ; thence to G, G, &c. ; till at last they meet in C ; where, by their union, they cause a much strong er sound than in any part of the segment whatever, even at A, the point from whence they came. Accordingly, all the
contrivance in whispering places is, that near the person who whispers there may be a smooth wall, arched either cylindri-, tally or elliptically. A circular arch will do, but not so well.
The most considerable whispering places in England are, the whispering gallery in the dome of St. Paul's, Lon don, where the ticking of a watch may be heard from side to side, and a very easy whisper be sent all round the dome. The famous whispering-place in Glouces ter Cathedral is no other than a gallery above the east end of the choir, leading from one side thereof to the other. It consists of five angles and six sides, the middlemost of which is a naked window, yet two whisperers hear each other at the distance of twenty-five yards.