Sound / by John Tyndall.

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

Licence: Public Domain Mark

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

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    copy of the wave canal of the brothers Weber. It is filled to the level A B with coloured water. By tilting the end a suddenly, a wave is generated, which moves on to B, and is there reflected. By sending forth fresh waves at the proper intervals, the surface is divided into two stationary undulations. Making the succession of impulses more rapid we can subdivide the surface into three, four (shown in the figure), or more stationary undulations, separated from each other by nodes. The step of a water-carrier is sometimes so timed as to throw the surface of the water in his vessel into stationary waves, which may augment in height until the water splashes over the brim. Practice Fig. 40. has taught the water-carrier what to do; he changes his step, alters the period of his impulses, and thus stops the accumulation of the motion While travelling, some years ago,1 in the coupe of French railway carriage I had occasion to place a bottle half filled with water on one of the little coupe tables. My companion observed it with thoughtful interest. At times it would be quite still; at times it would oscillate violently. To the passenger within the carriage there was no sensible change in the motion of the train to which the difference could be ascribed. But in the one case the tremor of the carriage contained no vibrations synchronous with the oscillating period of the water, while In the other case such vibrations were present. Out of the confused assemblage of tremors the water selected the 1 In company with Mr. Thomas Carlyle.