Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1881 Excerpt: ...p. 2S0; Phil. Mag., Nov. 1875 (Uh ser.), Vol. L, p. 416; Nature, Dec. 9, 1875, Vol. XIII, p. Hi; Monatsuer. Berl. Akad., Feb. 17, 1876; I'ogg. Ann., Vol. CLIX, p. 117; Monatab. Berl. Akad., Juno 7, 1877; Pogg. Ann., 1877, Vol. II, p. 521. It was, therefore, evident that the telephone could only respond to the effect produced in selenium at the moment of change from light towards darkness, or vice versa, and that it would be advisable to intermit the light with great rapidity so as to produce a succession of changes in the conductivity of the selenium corresponding in frequency to musical vibrations within the limits of the sense of hearing. For I had often noticed that currents of electricity, so feeble as hardly to produce any audible effects from a telephone when the circuit was simply opened and closed, caused very perceptible musical sounds when the circuit was rapidly interrupted; and that the higher the pitch of the sound the more audible was the effect. I was much struck by the idea of producing sound in this way by the action of light. I proposed to pass a bright light through one of the orifices in a perforated screen consisting of a circular disk or wheel with holes near the circumference. Upon rapidly rotating the disk an intermittent beam of light would fall upon the selenium, and a musical tone should be produced from the telephone, the pitch of which would depend upon the rapidity of the rotation of the disk. Upon further consideration, it appeared to me that all the audible effects obtained from variations of electricity could also be produced by variations Of light, acting upon selenium. I saw that the effect could not only be produced at the extreme distance at which selenium would normally respond to the action of a luminous body, but that...
"synopsis" may belong to another edition of this title.
