Morning journal and courier., 1880-08-30
THE PHOTOPHONE.

" HS udfO uOt yet CSdS6O GO WOuU0T aE the { success of the telephone in annihilating time and space, nor has that remarkable instru. ment yet reached the limit of it's powers. But invention is eager, and we are called upon to let the telephone and it's marvels go their way, and turn our attention to Q still more wonderful illustration of the properties of
 matter and the ingenuity of the nineteenth century man. This is the Photophons, which requires no clumsy lines of wire, but trans mits the human voice and other sounds by means of beam of light. The Photophone is the joint work of Alexander Graham Bell
 of telephone fame, and Mir. Summer Fainter
 MT. Bell has read an account of the pres- ent status of the Photophone before the meet ing of scientists at Boston. In their e1peri- ments he and his co-worker have found that many substances are sensitive to ight-vibra- tions. They have found this propertyi in seleni- um, gold, silver, platinum, iron, steel, brass, copper, zinc, lead, antimony, German silver, Jenkins metal, Babbitts metal, ivory, cellu- Ibid, gutta percha, hard rubber, soft vulcan ized rubber, paper, parchment, wood, mica and silvered glass; and the only substances from which they have not obtained results are carbon and thin microscopic glass. They have found that when 6 vibratory beam of light falls upon these substances they emit sounds,-the pitch of which depends upon the frequency of the vibratory change In the light. They have also found that when the form or character of the ight-vibration on selenium, and probably on the other sub stances, is controlled, the quality of the sound is controlled and all varieties of articu- late speech are obtained. They believe it possible thus without a conducting wire. as in electric telephony, to speak from station to station, wherever beam of light can be projected. They have not had an opportu- nifty of testing the limit to which this photo- phonic influence can be extended, but they have spoken to and from points about one- seventh of mile,apart.
 Messrs Bell and Fainter have devised about. fifty forms of photophonic apparatus, but the best and simplest consists of plane mirror of. flexible material-such as sil7ered mica or microscope glass. Against, the back of tlsis mirror the speakers voice is directed. The light reflected from this mirror is thus thrown into vibrations corresponding to those of the diaphragm itself. In arranging the sp- paratus for the purpose of reproducing sound at distance, any powerful source of light mented chiefly with sunlight For this pur- pose large beam is concentrated by means of a lens upon the diaphragm mirror, and, after reflection, is again rendered parallel by means of another lens. The beam is re- ceived at 8 distant station upon a parabolic reflector, in the focus of which Is placed @ sensitive selenium cell, connected in a local circuit with battery and telephone. A large number of trials of this apparatus have been made with the transmitting and receiving in struments so far apart that sounds could not be heard directly through the air. In labora- tory experiments the transmitting and receiv- ing instruments are necessarily within ear shot of one another, and they have, therefore, been accustomed to pooling the electric cir cult connected with the selenium receiver, so as to place the telephones in another room. By such experiments" says MT. Bell, five have found that articuIate speech can be re- produced by the o1y-hydrogen light, and even by the light of a kerosene lamp. The loudest effects obtained from light are pro- duced by rapidly interrupting the beam by the perforated disk. The great advantage of this form of apparatus for experimental work is the noiselessness of it's rota- tion, admitting the close approach of the receiver without interfering with the audibility of the effect heard from the latter for it will be understood that musical tones are emitted from the receiver when no sound is made at the transmitter. A silent motion thus produces a sound. In this way musical tones have been heard even from the light of candle. When distant effects arc sought another apparatus is used. By plao- ing an opaque screen near the rotating disk the beam can be entirely cut off by slight motion of the hand, and musical signals, like the dots and dashes of the Morse telegraph code, can thus be produced at the distant re- ceiving station"
 In May, 1878, MT. Bell told the Royal h. stitute of Great Britain that he believed it possible to hear shadow by interrupting the action of light upon selenium, and his and his co-workers achievements since show that he was not romancing. How use ful their Photopone will be remains to be seen It is certainly one of the most marvel ous of s'modern miracles