Tyndall, John, 1820-1893 · London : Longmans, Green · leaf 399
376 LECTURE VIII. … approach of the hands the vibrations of the two sectorsare intercepted; their interference right and left being thus abolished, the remain-ing sectors sound moreloudly. Passing the singlehand to and fro over thesurface, you also hear arise and fall of the sound.It rises when the hand isover a…
Sound
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