338 SCIENCE PROGRESS 



away, leaving the insoluble gum lines of varying width 

 constituting the image. 



The gum lines, fine though they may be, are sufficient to 

 make the style vibrate as it passes over them, when the print 

 is attached to the rotating drum of the transmitter. This 

 vibration is very detrimental to the telegraphing of the picture, 

 as instead of the impulses telegraphed depending for their 

 duration solely on the width of the lines, they tend to endure 

 for a time tjn, where t is the time taken for one revolution and 

 ;/ the number of lines traversed by the style in one revolution. 

 //// is of course constant, while the widths of the insulating 

 lines vary, and on their variation depends the formation of 

 the details in the picture. 



I overcame this as follows. First, the prints were made 

 on fairly thick lead-foil instead of copper, and afterwards they 

 were pressed so as to sink the lines completely into the metal, 

 and thus give a smooth surface. The style passes over the 

 photograph thus without any vibration. 



It will be readily seen that by passing the electric current 

 through the cylinder and style these lines are made to act as 

 interrupters, so that at the receiving station we get a series 

 of short-period currents, each of whose duration depends on 

 the thickness of the line corresponding. Instead of utilising 

 the received currents to cause a shutter to rise and so allow 

 the light from a lamp to act on a photographic film (as in the 

 case of the Korn telautograph), I pass them through a cylinder 

 and style similar to that used in the transmitter, but the cylinder 

 has attached to it a piece of electrically sensitised paper, which 

 discolours by electrolytic action every time the current flows 

 through it, thus leaving a black dot on the paper. These dots 

 form into lines as the transmission proceeds, and finally a 

 replica of the original half-tone photograph is obtained, the 

 thickness of the lines depending on the length of time of flow 

 of current, and thus corresponding exactly with those of the 

 picture transmitted. 



But here several line phenomena have to be dealt with. 

 The method adopted for strengthening the attenuated currents 

 I do not propose to discuss now, but the effects of the cable 

 capacity are worthy of notice. Oscillatory currents are appar- 

 ently formed in the line, and these flow into the receiver and 

 effectually blur and spoil the results ; indeed, they prevent the 



