408 FRAGMENTS OF SCIENCE. 



cive 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 indicated. You are almost sure to have caused 

 a bit of iron to hang from the end of your magnet, and 

 you have probably succeeded in causing a second bit 

 to attach itself to the first, a third to the second ; until 

 finally the force has become too feeble to bear the 

 weight of more. If you have operated with nails, you 

 may have observed that the points and edges hold to- 

 gether with the greatest tenacity ; and that a bit of 

 iron clings more firmly to the corner of your magnet 

 than to one of its flat surfaces. In short, you will in 

 all likelihood have enriched your experience in many 

 ways without any special direction from me. 



Well, the magnet attracts the nail, and the nail 

 attracts a second one. This proves that the nail in 

 contact with the magnet has had the magnetic quality 

 developed in it by that contact. If it be withdrawn 

 from the magnet its power to attract its fellow nail 

 ceases. Contact, however, is not necessary. A sheet of 

 glass or paper, or a space of air, may exist between the 

 magnet and the nail; the latter is still magnetised, 

 though not so forcibly as when in actual contact. The 

 nail thus presented to the magnet is itself a temporary 

 magnet. That end which is turned towards the mag- 

 netic pole has the opposite magnetism of the pole which 

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

 same magnetism as the pole itself, and between the 



