ELEMENTARY MAGNETISM 875 



a magnetic influence on your minds as to excite in them a 

 strong resolve to study natural philosophy. I should rather 

 be the gainer by my own utterance, and by the reaction of 

 your fervor. The magnet also is the gainer by the reac- 

 tion of the body which it magnetizes. 



Look now to your excited piece of steel; figure each 

 molecule with its opposed fluids spread over its opposite 

 faces. How can this state of things be permanent? The 

 fluids, by hypothesis, attract each other; what, then, keeps 

 them apart? Why do they not instantly rush together 

 across the equator of the atom, and thus neutralize each 

 other? To meet this question, philosophers have been 

 obliged to infer the existence of a special force, which 

 holds the fluids asunder. They call it coercive force; and 

 it is found that those kinds of steel which offer most re- 

 sistance to being magnetized — which require the greatest 

 amount of * 'coercion" to tear their fluids asunder — are the 

 very ones which offer the greatest resistance to the re- 

 union of the fluids after they have been once separated. 

 Such kinds of steel are most suited to the formation of 

 permanent magnets. It is manifest, indeed, that without 

 coercive force a permanent magnet would not be at all 

 possible. 



Probably long before this you will have dipped the 

 end of your magnet among iron filings, and observed how 

 they cling to it; or into a nail-box, and found how it 

 drags the nails after it. I know very well that if you 

 are not the slaves of routine you will have by this time 

 done many things that I have not told you to do, and 

 thus multiplied your experience beyond what I have in- 

 dicated. You are almost sure to have caused a bit of 

 iron to hang from the end of jour magnet, and you have 



