CHAP, iv.] ELECTRIC TELEGRAPHY. 605 



placed parallel to the lowest line of the receiving cylinder and a little 

 distance below it, and suppose the apparatus at work. Every time 

 that the current passes along the line, that is, as often as the style of 

 the transmitter encounters the insulating parts- or the lines of the 

 message, the paper is raised by the motion of a tongue and is applied 

 against the point of the raised helix which happens to be at that 

 moment on the lowest line. During the complete turn described 

 simultaneously by each apparatus, this contact is made and broken as 

 often as the tracing style encounters or leaves the marks of the 

 message. Now the raised helix being constantly damped with thick 

 ink from a roller, the result is a series of points or black marks on a 

 straight line across the breadth of the paper, reproducing identically 

 the figure of the line encountered by the tracing style in one turn of 

 the message. Since the paper moves on the cylinder, so as to advance 

 at each turn by a quantity equal to the intervals between the spiral 

 turns of the style, there will be at last on the receiving sheet a suc- 

 cession of marks which together will give us a facsimile of the 

 message. 



Like Caselli's telegraph, Meyer's requires a perfect synchronism of 

 the movements of the apparatus in the departure and arrival stations. 

 The whole question is consequently to regulate the clockwork which 

 moves the apparatus. We perceive that if Caselli's apparatus is a 

 combination of Bain's electro-chemical telegraph with a particular 

 mechanism, the synchronism of which is regulated by electricity, 

 Meyer's apparatus may be considered as a combination of Caselli's 

 telegraph with certain parts of Morse's and Hughes' system. 



