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In less than six months we'll be filling contracts here in America. Two months later we'll be introducing into seven different countries in Europe a fully protected and patented transmitting camera as far ahead of the old-fashioned photophone as a Bell telephone is ahead of a tin speaking-tube." "I know, Jim; but you must be more careful! You must, in some way, stop working so hard!"
Perhaps the greatest wonders of the 19th century were the invention of photography, solar spectral analysis, the radiometer, the phonograph, the photophone; in public affairs, the reunion of the old and new school Presbyterian Churches, and the disappearance, by civil war, of negro slavery in the United States.
Selenium even emits notes under a vibratory beam of light, the pitch depending on the frequency. Changes in the intensity of the light focused by the reflector on the cell alter its electrical resistance and vary the current from the dry batteries. Hence the telephone receiver over there is affected. Bell used the photophone or radiophone over several hundred feet, Ruhmer over several miles.
'This crowning marvel of the electric telegraph, as Sir William Thomson happily expressed it, was followed by another invention in some respects even more remarkable. During the winter of 1878 Professor Bell was in England, and while lecturing at the Royal Institution, London, he conceived the idea of the photophone.
"I knew we should need some means to communicate with Herndon," he explained simply, "and the wireless telephone wasn't practicable. So I have used Dr. Alexander Graham Bell's photophone. Any of the lights on this side of La Montaigne, I knew, would serve. What I did, Walter, was merely to talk into the mouthpiece back of this little silvered mirror which reflects light.
The action of the photophone is based on the peculiar fact observed in 1873 by Mr J E Mayhew, that the electrical resistance of crystalline selenium diminishes when a ray of light falls upon it.
The spectroscope has demonstrated the truth of the poet, who said that 'light is the voice of the stars, and we have it on the authority of Professor Bell and M. Janssen, the celebrated astronomer, that the changing brightness of the photosphere, as produced by solar hurricanes, has produced a feeble echo in the photophone.
This is the phenomenon which, as you know, has been utilized by Prof. Graham Bell in that most ingenious and striking invention, the photophone. By the kindness of Prof. Silvanus Thompson, I have a few slides to show the principle of the invention, and Mr. Shelford Bidwell has been kind enough to lend me his home-made photophone, which answers exceedingly well for short distances.
Selenium even emits notes under a vibratory beam of light, the pitch depending on the frequency. Changes in the intensity of the light focused by the reflector on the cell alter its electrical resistance and vary the current from the dry batteries. Hence the telephone receiver over there is affected. Bell used the photophone or radiophone over several hundred feet, Ruhmer over several miles.
They said they were going in the direction opposite from you." "Well?" I asked, mystified. "What of it? I know all that, already." "But Dillon doesn't," replied Garrick, in great excitement now. "I knew that we should have to have some way of communicating with him instantly if this fellow proved to be as resourceful as I believed him to be. So I thought of the radiophone or photophone of Dr.
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