ELEMENTARY MAGNETISM. 357 



excites it; the end most remote from the pole has the 

 same magnetism as the pole itself, and between the 

 two poles the nail, like the magnet, possesses a mag- 

 netic equator. 



Conversant as you now are with the theory of mag- 

 netic fluids, you have already, I doubt not, anticipated 

 me in imagining the exact condition of an iron nail 

 under the influence of the magnet. You picture the 

 iron as possessing the neutral fluid in abundance; you 

 picture the magnetic pole, when brought near, decom- 

 posing the fluid; repelling the fluid of a like kind with 

 itself, and attracting the unlike fluid; thus exciting in 

 the parts of the iron nearest to itself the opposite po- 

 larity. But the iron is incapable of becoming a perma- 

 nent magnet. It only shows its virtue as long as the 

 magnet acts upon it. What, then, does the iron lack 

 which the steel possesses? It lacks coercive force. Its 

 fluids are separated with ease; but, once the separating 

 cause is removed, they flow together again, and neu- 

 trality is restored. Imagination must be quite nimble 

 in picturing these changes able to see the fluids di- 

 viding and reuniting, according as the magnet is 

 brought near or withdrawn. Fixing a definite pole in 

 your mind, you must picture the precise arrangement 

 of the two fluids with reference to this pole, and be 

 able to arouse similar pictures in the minds of your 

 pupils. You will cause them to place magnets and iron 

 in various positions, and describe the exact magnetic 

 state of the iron in each particular case. The mere 

 facts of magnetism will have their interest immensely 

 augmented by an acquaintance with the principles 

 whereon the facts depend. Still, while you use this 

 theory of magnetic fluids to track out the phenomena 

 and link them together, you will not forget to tell your 

 pupils that it is to be regarded as a symbol merely, 



