Tyndall, John, 1820-1893 · London : Longmans, Green · leaf 85
64 LECTURE II. … pair of toothed wheels (seen when the back of the instru-ment is turned towards you). As the disc and its axisturn, these wheels rotate. In front you simply see twograduated dials, fig. 28, each furnished with an index likePj^ 28 ^^® hand of a clock. These indexes record thenumber of…
Sound
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