ON SOME MARVELS IN TELEGRAPHY. 



257 



successive strokes of a movable pointer, along which the 

 current flows ; but the principle is the same. 



It is essential, in such a process as I have described 

 first, that the recording sheet should be carried athwart the 

 pointer which conveys the marking current (or the pointer 

 carried across the recording sheet) in precise accordance 

 with the motion of the transmitting sheet athwart the wire 

 or style which conveys the current to the long wire between 

 the stations (or of this style across the transmitting sheet). 

 The recording sheet and the transmitting sheet must also 



be shifted between each stroke by an equal amount The 

 latter point, is easily secured; the former is secured by 

 causing the mechanism which gives the transmitting style 

 its successive strokes to make and break circuit, by which 

 a temporary magnet at the receiving station is magnetized 

 and demagnetized ; by the action of this magnet the re- 

 cording pointer is caused to start on its motion athwart the 

 receiving sheet, and moving uniformly it completes its 

 thwart stroke at the same instant as the transmitting style. 



Caselli's pantelegraph admirably effects the transmission 

 of facsimiles. The transmitting style is carried by the 

 motion of a heavy pendulum in an arc of constant range 

 over a cylindrical surface on which the paper containing the 



s 



