CHAP, iv.] ELECTRIC TELEGRAPHY. 579 



its action. The armature, or light lever, is attracted and comes in con- 

 tact with the left hand screw, giving passage to the current which 

 passes on to the bobbin of the indicator, at the same time closing the 

 circuit in the local battery. The action of this latter battery is thus 

 added to that of the line-current in- moving the writing lever of the 

 indicator R. When the line-current is interrupted, the polarization of 

 the electro-magnet of the relay ceases, the armature is brought into 

 contact with the right hand screw, and the circuit of the local battery 



PIG. 376. Indicator of Morse Digney system. 



is left open at the same time that the indicator ceases to receive any 

 line-current. 



There are different systems of relays ; the one represented in Fig. 

 375 and separately in Fig. 374 is clue to M. Froment. 



The indicator of the Morse telegraph, as worked on the telegraphic 

 lines of England and France, at least, has been modified and im- 

 proved by Mr. Digney, by substituting for scratches, marks made with 

 ink which require less force in making. For this reason the Morse- 

 Digney system requires no relays for working. Figs. 376 and 377 



p p 2 



