Tyndall, John, 1820-1893 · New York, Collier · leaf 114
acquainted. The disks ofthe two sirens have a common axis, so that when onedisk rotates the other rotates with it. As in the formercase, the number of revolutions is recorded by clock-work (omitted in the figure). When air is urged throughthe tube t the upper siren alone sounds; when urged 1 It is… … 111 112 SOUND through t, the lower one only sounds; when it is urgedsimultaneously through f and 2, both the sirens sound.With this instrument, therefore, we are able to introducemuch more varied combinations than with the formerone. Helmholtz has also contrived a means by whichnot only the disk of…
Sound
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