28 Tlature'0 



electric current. Now break the current, and 

 the little natural magnets, that have been so 

 ruthlessly torn from their home circle attach- 

 ments, fly back to them again with the speed 

 of lightning, and the iron rod as a whole is 

 no longer a magnet. The power to become so 

 under the electrical strain is in it still only 

 latent. 



The kind of magnet that we have been 

 describing is called an electromagnet. It is 

 a magnet only so long as the electric current 

 is passing around it. There is anotlu-r kind 

 of magnet called a permanent magnet that wiU 

 remain a magnet after the current is taker, 

 away. The permanent magnet is made of 

 steel and hardened; then its poles are placed 

 to the poles of a powerful magnet, either elec- 

 tro or permanent, when its molecular rings 

 are wrenched apart and arraiiirrd in a polari/cd 

 position as heretofore described. Now take it 

 away from the magnet and it will be found to 

 retain its magnetism. The molecules tend tc 

 fly back the same as those of the soft iron, but 

 they cannot because hardened steel is so much 

 finer grained than soft iron, and the molecules 

 are so close together that they are held in' 

 position by a friction that is called its coercive 

 force. The soft iron is comparatively free 

 from this coercive force, because its molecules 

 are free to move on each other, so that when 

 they are wrenched out of their natural position 



