836 Mr. T. Thome Baler [April 22, 



Instances of its use may be recognised in the publication of 

 photographs 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 MiiTor ' may be called a practical 

 modification of several early attempts. The effect of an electric 

 current to discolour certain suitable electrolytes or to set free an 

 element or ion that can be used to form with a second substance 

 a coloured 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 coloured marks which join 

 up en masse to form a new image. My 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 photograph 

 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 

 coloured 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 two hundred 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 the figure. The transmitting instrument 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 

 and shade of the picture is made up of masses of thinner or thicker 

 lines, with clear spaces in between. 



As the stylus traces over such a photograph, its contact with the 

 metal base is interrupted every time one of these fish-glue lines comes 

 beneath it, and for such a time as depends, of course, on the width of 

 the line. The transmitting instrument thus sends into the telegraph 

 lines a series of electric currents whose periods of duration are deter- 

 mined by the width of the fines composing the photograph. 



A similar stylus So traces an exactly similar path over a revolving 

 drum in the receiving instrument, but round this drum is wrapped 



