Notice of the Proceedings at the Meetings of the Members of the Royal Institution of Great Britain, Vol. 17

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Excerpt from Notice of the Proceedings at the Meetings of the Members of the Royal Institution of Great Britain, Vol. 17: With Abstracts of the Discourses Delivered at the Evening Meetings, 1902 0904 AS a source of sound a bird-call is usually convenient. A stream of air from a circular hole in a thin plate impinges centrically upon a similar hole in a parallel plate held at a little distance. Bird-calls are very easily made. The first plate, of 1 or 2 cm. In diameter, is cemented, or soldered, to the end of a short supply-tube. The second plate may conveniently be made triangular, the turned down corners being soldered to the first plate. For calls Of medium pitch the holes may be made in tin plate. They may be as small as mm. In diameter, and the distance between them as little as 1 mm. In any case the edges of the holes Should be sharp and clean. There is no difficulty in Obtaining wave-lengths (complete) as low as 1 cm., and with care wave-lengths Of '6 cm. May be reached, cor responding to about vibrations per second. In experimenting upon minimum wave-lengths, the distance between the call and the ¿ame should not exceed 50 Cm., and the ¿ame Should be adjusted to the verge Of ¿aring.* As most bird-calls are very dependent upon the precise pressure of the wind, a manometer in immediate connec tion is practically a necessity. The pressure, originally somewhat in excess, may be controlled by a screw pinch-cock Operating on a rubber connecting tube. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.