HISTORY AND PROGRESS. 



69 



a signal arriving from either side, L or L', will be given 

 notice of by the alarms A and A'. In this way the current 

 from the left goes from L, past a lightning guard, e, 

 through a galvanoscope, G, L, N, s, alarm A, earth, and back 



LJ 



Fig. 35. 



again. Arriving by L', a current passes the lightning guard 

 e'j G', L', N', s', alarm A', earth, and so on. 



When a signal is given from L, the employe turns his 

 switch N on r. The current passes then from L through the 

 galvanoscope G, the needle of which it deflects, L, N, r, disc, 

 contact-lever, p, R, receiving instrument, earth, &c. 



Breguet has also made use of an idea used previously in 

 the construction of telegraphs in Germany. Instead of 

 the movable armature and stationary electro-magnets, he 

 sometimes employs a cylindrical electro-magnet made to turn 

 on its longer axis on screw points. The poles of the soft 

 iron core are furnished with soft iron continuations, which 

 hang down between the opposite poles of two permanent 

 horseshoe magnets. "When the current magnetises the soft 

 iron core arid its continuations, the coil with core and con- 

 tinuations are deflected to one side or to the other, attracted 

 by one of the permanent magnets, and repelled by the other. 



