19 December 2002
BELL, Alexander Graham (1847-1892), Inventor. Autograph manuscript, comprising notes from Bell's experiments with the Photophone, n.p., 26 April to 1 May 1880. 12 leaves of coated photographic paper, 2 with notes, 7 numbered or dated, 4to (12 x 9 in.), in black ink on rectos only, the paper lightly oxidized to brownish gray, not affecting legibility..
BELL'S PIONEERING EXPERIMENTS WITH THE PHOTOPHONE
In 1880, only four years after his invention of the telephone, Bell began work on a device he dubbed the photophone, a technology that strongly foreshadows modern wireless communication. The photophone, in Bell's conception, would allow sound to be transmitted on a beam of sunlight that would be reflected simultaneously with sound waves projected toward a mirror. Its power source was a selenium cell.
These cryptic, rather disjointed notes pertain to Bell's tests on a selenium preparation for the photophone that he conducted with his cousin Chichester Bell and Sumner Taintor. Bell writes: "Fig. 1 is a plan and Fig. 2 a sectional view...After the varnish wind them up together into the form of a double spiral as shown in Fig. 1...[when] the spiral is formed fill all...bake until it is hard action of light strips of metal originated with Mr. [Chichester] Bell, who proposed to insulate them from one another by strips of mica wound I claim...the method of insulation by Japan varnish and the electro-plating process form the raised metalic ridges...and the area of selenium."
Bell believed that the photophone was his most important invention, but its success was severely limited by uncooperative weather conditions and the modest power provided by the selenium cell.
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