Sound / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1883
Catalogue details

Licence: Public Domain Mark

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

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    75/494 (page 53)
    pressure, the pitch instantly falls; resuming the pressure, it again rises; and thus by the alteration of the pressure we obtain great variations of tone. Nor are such rockers essential. Allowing one face of the clean square end of a heated poker to rest upon the block of lead, a rattle is heard; causing another face to rest upon the block, a clear musical note is obtained. The two faces have been bevelled differently by a file, so as to secure different rates of vibration.1 This curious effect was discovered by Schwartz and Trevelyan.2 § 3. Musical Sounds produced by Puffs. Professor Kobison was the first to produce a musical sound by a quick succession of puffs of air. His device was the first form of an instrument which will soon be in- troduced to you under the name of the syren. Eobison describes his experiment in the following words: ' A stopcock was so constructed that it opened and shut the passage of a pipe 720 times in a second. The apparatus was fitted to the pipe of a conduit leading from the bellows to the wind-chest of an organ. The air was simply allowed to pass gently along this pipe by the opening of the cock. When this was repeated 720 times in a second, the sound gin alt-was most smoothly uttered, 1 When a rough tide rolls in upon a pebbled beach, as at Blackgang Chine or Freshwater Gate in the Isle of Wight, the rounded stones are- carried up the slope by the impetus of the water, and when the wave re- treats the pebbles are dragged down. Innumerable collisions thus ensue of irrecrular intensity and recurrence. The union of these shocks produces a kind of scream. Hence the line in Tennyson's Maud:— 1 Now to the scream of a maddened beach dragged down by the wave.' The height of the note depends in some measure upon the size of the pebbles, varyiDg from a kind of roar—heard when the stones are large— to a scream; from a scream to a noise resembling that of frying bacon ; and from this, when the pebbles are so small as to approach the state of gravel, to a mere hiss. The roar of the breaking wave itself is mainly due to tho explosion of bladders of air. • Heal, a Mode of Motion, Sixth ed., p. 96.