78 THE ELECTRIC TELEGRAPH. 



separate magnets were combined in the form of a battery ; 

 because the poles, acting at the same time upon the armature, 

 produce along its whole length on each side an uniform 

 magnetism, so that the wire coil receives, in every point, the 

 same magneto-electric impulse. 



The interior of the indicator is shown in Fig. 41. The 

 top s s of a permanent magnet of hard steel, bent in a 

 rectangular form, and having a space cut out of its upper 

 end, protrudes through the side of a circular brass plate, A A, 

 one- eighth of an inch thick. In the slit in the upper end 

 s s of the magnet is the axis of a movable tongue of soft 

 iron, having at its extremity the same polarity as the end s, 

 and vibrating between the poles n and s of a polarised 

 electro-magnet, m m. By polarised is meant that the soft 

 iron cores around which the wire is wound receive polarity 

 from a permanent magnet. 



In this case the cores of the electro-magnet are attached 

 to a stout piece of soft iron, resting on the north pole of 

 the angular magnet which distributes to the whole system 



Fig. 41. 



above the point of contact north polarity. The tongue or 

 armature of soft iron is, therefore, attracted by both the 

 poles of the electro-magnet with equal force, and if not 

 exactly balanced in the middle between them, will rest on 

 one side or on the other by the superior attraction of the 

 nearer pole. 



