AN EXTRAORDINARY DISCOVERY.

Star (Christchurch), Issue 8832, 19 January 1907, Page 4

AN EXTRAORDINARY DISCOVERY.

TELEGRAPHING PHOTOGRAPHS OVER 1000 MILES. The transmission of a visual image along the eleotrio wire lias long been one of the dreams of science, and has been regarded as little better than a chimera. Many years ago the public was hoaxed with a marvellously realis-„ tic description of how an Australian man of science had -transmitted to a great distance the image of the scene on a racecourse. The instrument that will make speakers on the telephone visible to each other may still be some distance ahead, but .here is actually in Existence a machine which can with wonderful sucoess transmit photographs to a distance of more than a thousand miles, and reproduce them, slightly blurred, it is true, but perfectly recognisable. The invention is due to a young German man of science, Professor Korn, of the University of Munich.. Some time, ago illustrations of the machine iix ats more elementary form were given, with the somewhat dim but still promising effects which were obtained in 1903. Recently, however, the inventor has greatly improved this apparatus, and the really extraordinary results that he has obtained' have been illustrated. The possibility of thie remarkable electrioal mechanical feat is due to a peculiar property of the metal, selenium, which can translate variations of light into concomitant variations of an eleotrio current. Just as the diaphragm of a telephone causes the mechanical vibrations of sound to be reproduced in corresponding electric vibrations, so the action of variable light upon a plat© of selenium, through which a current of electricity is passing, will cause that current to vary in ; exact accordance with the gradation of the light modified by a photographic film. | Like a telegraph or a telephone, there is at ono end a transmitter, at the other end a receiver. In its simplest form tho receiver consists of an outer metallic cylinder, and an inner cylinder of glans, on which is fixed the photographic film to be transmitted. The inner cylinder is made to revolve, j and as it does so it passes an aperture in the metal cylinder, through which comes a focutssed beam from a Nernst ; lamp. Th:» beam passes through the photographic film and thence to a : prism, from which it is deflected to a plaque of selenium in the electrio cir- j cuit. The variations of the revolving image are thus made to play upon the selenium, and are echoed, as it were, j ;by the electric wave passing through the selenium. The receiver consists primarily of a camera in which is another revolving cylinder carrying a sensitive film wliich is to receive the image. Through an aperture in the j end ef the camera comes another beam j from a Nernst lamp which has previous- J ly been focuesed upon a Geiesler tube, j I The tube is in the electric circuit, and ! the variations of the current are thus ' retranslated into variations of light, which, playing upon the sensitive film, set up the second" image. In his instali lation ProfefcfiOT Korn used a resistance ' which was exactly equivalent to that | which would have been obtained by 1125 miles of telegraph wire, co that i for all practical purposes the transmitter and receiver were that distance apart. The inventor hopes to be able ! one day to telegraph a photograph to New York in a quarter of an hour. With his present apparatus he can make his reproduction in twelve minutes but the resistance of submarine cables is so high that he would require longer time to send hist picture across the Atlantic. The invention when perfect will be a godsend to the' illustrated Press. It is owing to the enterprise of " 1' Illustration " that the first account of Professor Kern's discovery has beon given -to the world.