Telegraphic Photography and Electric Vision

THE success achieved by Dr. A. Korn in the telegraphic transmission of photographs (NATURE, vol. Ixxvi., p. 444) has been followed by a remarkable development of inventive activity in the same line. Among several new processes which have recently claimed public attention three of the most promising were described in detail at the April meeting of the Société Françhise de Physique. As in Dr. Korn's method, the reproduced picture is in all cases constituted by a close spiral line of varying intensity traced upon a photographic film, or other material, covering a cylinder which rotates synchronously with another cylinder in the transmitting instrument. The use of selenium for controlling the resistance of the circuit is, however, generally discarded, the requisite variations of current being effected by purely mechanical means; ordinary film negatives, therefore, cannot be used.