Tyndall, John, 1820-1893 · New York, Collier · leaf 415
or desirable. The instrument, as already stated, consists of two ofDoves sirens, cf and C, connected by a common axis, theupper one being turned upside down. Each siren is pro-vided with four series of apertures, numbering as follows: Upper siren Lower siren Number of apertures Number of apertures… … Sia. SOUND 413 urge air through the instrument; both sounds flow to-gether in perfect unison; the unison being maintained,however the pitch may be exalted. We have, however,already learned (Chapter II.) that by turning the handleof the upper siren the orifices in its wind-chest c arecaused either…
Sound
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