CII. XXXV. 



THE INDUCTION COIL. 



351 



To try this he wound from 200 to 300 yards of wire 

 round a hollow cylinder a. Fig. 59, and carried the two 

 ends of the wire to a little instrument by called a galvano- 

 meter, which was invented by Ampbre, and the needle of 

 which moves directly the slightest current passes through it. 

 He then took a powerful bar magnet, c, and held it within the 

 cylinder. The moment he put it in, the needle of the galvano- 

 meter showed that an electric current had passed through 



Fig. 59. 



Faraday's Experiment on creating an Electric Current by means of a Magnet 

 (Ganot). 



tf , Coil of wire round a wooden cylinder connected at the two ends with ^, a galvano- 

 meter, the needle of which shows directly a current passes through the wire ; c, a 

 powerful magnet. 



the wire in one direction, and the moment he drew it out 

 another rush of electricity occurred in the other direction, 

 showing that the magnet had set up an electric current in a 

 coil of wire. While the magnet remained in the cylinder 

 there was no current j it was only at the moment of going in 

 and coming out that it produced the effect. By a more 

 complicated apparatus Faraday succeeded in making these 

 currents strong enough to produce electric sparks ; and it is 



