Tyndall, John, 1820-1893 · London : Longmans, Green · leaf 398
. Drawing a bowover the edge of a brass disc, I divide it into six vibratingsectors. When the palm of the hand is brought over anyone of them, the sound, instead of being diminished, isaugmented. When two hands are placed over twoadjacent sectors, you notice no increase of the sound ; butwhen they… … 376 LECTURE VIII.
Sound
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