Gbeorg anD "nature of Aagnetfem. 29 



they fly back by their own attractions as soon 

 as the force holding them apart is taken away. 

 The molecules of hardened steel are unable to 

 fly back, although they tend to do it just as 

 much as in the iron, and so it is called a per- 

 manent magnet. Its molecules also are under 

 a strain, like a bent bow. (The form of such 

 a magnet is usually that of a horse-shoe, or U.) 

 Let us use a homely illustration that may 

 help us to understand. Let ten boys represent 

 the molecules in a piece of iron. Let them 

 pair off into five pairs and each one clasp his 

 mate in his arms; each one, say, is exerting a 

 force of ten pounds, and it would require a 

 force of twenty pounds to pull any one of the 

 pairs apart. The five pairs are exerting a 

 force of one hundred pounds, but this force is 

 not felt outside of themselves. Now let them 

 unclasp themselves and take hold of a rope 

 that is tied to a post, and all pull with the 

 same force that they were using, to wit, ten 

 pounds each, and all pull in the same direc- 

 tion, and they would put a strain of one 

 (ni ud red pounds upon the post, the same power 

 that they \vcn- exerting upon themselves be- 

 fore they combined their efforts on something 

 onKiile df them-elves. So with the magnet. 



ng MS the force of each molecule is wholly 

 spent upon it- ni-i^hlmr there U nothing left. 



KteriOT DM. Uut as soon ;is they nil line 

 Up and pull conjointly in the .same direction 



