194 



MAGNETS. 



FIG. 132. 



321. Armatures. Magnets left to themselves would soon 

 lose their magnetism by the recombination of their magnetic fluids, 

 They must therefore be provided with armatures. 

 Armatures are pieces of soft iron placed in contact with 

 opposite poles, as shown in Fig. 133. The two poles 

 of the magnet (or magnets, for two bar 

 magnets may be thus protected) act 

 inductively upon the armature and 

 produce in it poles opposite in kind 

 to those with which they come in con- 

 tact. The poles of the armature in turn 

 react upon the magnet, and, by their 

 power of attraction, aid in preventing 

 the recombination of the fluids in the 

 magnet. The armature is sometimes 

 the iron axle of a brass wheel ; it is 

 then called a rolling armature. Hold 

 a horse-shoe magnet by its middle, 

 slightly depress the poles, place the 

 wheel upon the arms of the magnet as 

 shown in Fig. 134, and allow it to roll 

 to the end. Its momentum will carry p 1G I3 ^ 

 the axle around the ends of the mag- 

 net, and the wheel will roll back to the middle, with the axle on 

 the under side of the magnet. 



FIG. 133. 



