376 FRAGMENTS OF SCIENCE 



probably succeeded in causing a second bit to attach itseH 

 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 together 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 expe- 

 rience 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 If it be withdrawn from the magnet its 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 magnetized, 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 

 toward the magnetic 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 be- 

 tween the two poles the nail, like the magnet, possesses 

 a magnetic equator. 



Conversant as you now are with the theory of magnetic 

 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 pos- 

 sessing the neutral fluid in abundance; you picture the 

 magnetic pole, when brought near, decomposing the fluid; 

 repelling the fluid of a like kind with itself, and attract- 

 ing the unlike fluid; thus exciting in the parts of the 



