Tyndall, John, 1820-1893 · New York : Appleton · leaf 95
tion. In my hands is held a small looking-glass, whichreceives the reflected beam, and from which it is againreflected to the screen, forming a small luminous diskupon the white surface. The disk is perfectly motionless;but the moment the fork is set in vibration the reflectedbeam is tilted rapidly…
Sound
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