Sound / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1875
Catalogue details

Licence: Public Domain Mark

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

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    therefore, is perceived as the train passes the station.1 This is the basis of Doppler’s theory of the colored stars. He supposes that all stars are white, but that some of them are rapidly retreating from us, thereby lengthening their luminiferous waves and becoming red. Others are rapidly approaching us, thereby shortening their waves, and be- coming green or blue. The ingenuity of this theory is extreme, but its correctness is more than doubtful. § 13. Transmission of Musical Sounds by Liquids and Solids. We have thus far occupied ourselves with the trans- mission of musical sounds through air. They are also transmitted by liquids and solids. When a tuning-fork screwed into a little wooden foot vibrates, nobody, except the persons closest to it, hears its sound. On dipping the foot into a glass of water a musical sound is audible: the vibrations having been transmitted through the water to the air. The tube m n, fig. 30, three feet long, is set upright upon a wooden tray a b. The tube ends in a funnel at the top, and is now filled with water to the brim. The fork F is thrown into vibration, and on dipping its foot into the funnel at the top of the tube, a musical sound swells out. I must so far forestall matters as to remark, that in this experiment the tray is the real sound- ing body. It has been thrown into vibration by the fork, but the vibrations have been conveyed to the tray by the water. Through the same medium vibrations are com- municated to the auditory nerve, the terminal filaments of which are immersed in a liquid : substituting mercury for water, a similar result is obtained. 1 Experiments on this subject were first made by M. Buys Ballot on the Dutch railway, and subsequently by Mr. Scott Russell in this country. Doppler’s idea is now applied to determine, from changes of wave-length, motions in the sun and fixed stars.