Abstract
THE first two sentences in Dr. Gripenberg's letter are misleading in the sense that they suggest that the only photo-electrical equipment capable of being used with “speaking-films” is the antimonite cell. It is well known, of course, that other substances besides selenium respond to fluctuations of light intensity, and antimonite is, apparently, one of them. Another is the “thalofide cell,” which has recently been advertised extensively, and wras invented by T. W. Case. I believe I am correct in saying that the sensitive substance in this cell is thallium sulphide. The comparative merits of these various substances will, no doubt, ultimately decide which is best to use with speaking-films. For the present, at any rate, selenium has been by no means completely ousted—a fact which is made evident by its adoption and use in connection with the film-photophone of Mr. Bergland, to the efficient performance of which attention has been directed by the Times correspondent.
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The Film-Photophone. Nature 108, 307 (1921). https://doi.org/10.1038/108307b0
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DOI: https://doi.org/10.1038/108307b0
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