258 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



spaces recombined form words and messages; squares of different 

 densities recombined, in correct position, form a photograph. 



I propose to deal with the more practical system first, which, as 

 already pointed out, is perhaps the less interesting from the theo- 

 retical point of view. The telectrograph system has been employed 

 by the Daily Mirror for the transmission of photographs since July, 

 1909, and has been worked very regularly between Paris and London, 

 and Manchester and London. 



Instances of its use may be recognized in the publication of photo- 

 graphs taken in court in the recent Steinheil case at Paris, when 

 photographs of witnesses or prisoners were sometimes received in 

 London actually before the court rose at which they were taken, a 

 clear day being gained in the time of publication. 



The method of telegraphing photographs that has been employed 

 on a large scale by the Daily Mirror may be called a practical modi- 

 fication of several early attempts. The effect of an electric current 

 to discolor certain suitable electrolytes or to set free an element or 

 ion that can be used to form with a second substance a colored 

 product was employed in many early forms of instruments for 

 telegraphing writing, etc. If we break up a photographic image in 

 the way already described into lines which interrupt the current for 

 periods depending on their width, these interrupted currents can be 

 used at the receiving station to form colored marks which join up 

 en masse to form a new image. IMy telectrographic process is thus 

 briefly as follows: 



At the sending station we have a metal drum revolving under an 

 iridium stylus, to the drum being attached a half-tone photogTaph 

 printed on lead foil. Current flows through the photographic image 

 to the line and thence to the receiver. The receiver consists of a 

 similar revolving metal drum over which a platinum stylus traces. 

 Every time the transmitter style comes in contact with a clear part of 

 the metal foil current flows to the receiver, and a black or colored 

 dot or mark appears on the chemical paper. But you will readily 

 understand that if our reproduction — built up of these little marks, 

 which have to be made at the rate of some 200 per second — is to be 

 accurate, each mark must be only exactly as long, in proportion, as 

 the clear metal space traversed by the stylus. 



It will be easier to explain the system by means of the rough 

 diagram shown in figure 1. The transmitting instriunent is shown on 

 the left, the receiver on the right. A metal drum is revolved by a 

 motor, one revolution every two seconds; over this a metal stylus or 

 needle traces a spiral path in the same way as a phonograph. On 

 the drum is fixed a half-tone photograph broken up into lines, and 

 printed in fish glue upon a sheet of lead foil. I will show one of 

 these line photographs on the screen, and you will see that the light 



