14 PHOTO-TELEGRAPHY 



current would pass through the film in the line 

 of least resistance. 



Charbonelle's receiver is also one that has been 

 suggested by some of the earlier workers ; he 

 passes the received current into a microphone, in 

 the centre of the diaphragm of which is a hardened 

 point ; this point of course vibrates in the same 

 manner as the diaphragm. The microphone is 

 brought down over the cylinder of the receiving 

 apparatus until it presses on an outer sheet of paper 

 wrapped round it ; under this outer paper is, first, 

 a sheet of carbon paper, and second, another sheet 

 of plain paper. As the microphone diaphragm 

 vibrates in response to the interruptions of the 

 current, so the point digs into the outer paper and 

 the mechanical pressure causes a carbon mark on 

 the inner paper. The results are stated to be good, 

 but the method is not likely to be of use for long 

 distances. 



Berjonneau has worked out a method of trans- 

 mitting half-tone photographs made with a single - 

 line screen, the receiver containing a minute shutter 

 which cuts off or allows to pass the rays from a lamp 

 concentrated on a revolving sensitive film. I Have 

 seen a promising result obtained with his appa- 

 ratus,* but detailed particulars of his system are 

 not yet available. He has, however, made trans- 

 missions over a telegraph line from Paris to Eng- 

 * Shown at Soc. Ing. Civ., Paris. 



