Sound / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Sound / by John Tyndall. Source: Wellcome Collection.

    80/496 (page 56)
    and alternately increasing and relaxing its speed, the sound rises and falls like the loud wail of a changing wind. § 4. Musical Sounds produced by a Tuning-fork. Various other means may be employed to throw the air into a state of periodic motion. A stretched string pulled aside and suddenly liberated imparts vibrations to the air which succeed each other in perfectly regular intervals. A tuning-fork does the same. When a bow is drawn across the prongs of a tuning-fork, fig. 20, the Fig. 20. resin of the bow enables the hairs to grip the prong, which is thus pulled aside. But the resistance of the prong soon becomes too strong, and it starts suddenly back; it is, however, immediately laid hold of again by the bow, to start back once more as soon as its resistance becomes great enough. This rhythmic process, continually repeated during the passage of the bow, finally throws the fork into a state of intense vibration, and the result is a musical note. A person close at hand could see the fork vibrating; a deaf person bringing his hand suffi- ciently near would feel the shivering in the air. Or causing its vibrating prong to touch a card, the taps