MAGNETISM. 101 



quires north, and the remote one south polarity, and 

 mutual attraction results. By virtue of its ac- 

 quired or induced magnetism, it will attract an- 

 other piece of iron, as is represented in the figure, 

 and affect it in all respects similarly. From the 

 second key, another smaller one may be sus- 

 pended, and from this another, and so on. It is 

 only necessary, that each successive object shall be 

 smaller than the one to which it is attached. The 

 magnetism thus acquired is only temporary in the case 

 of iron, but in the case of steel it is, in some degree 

 permanent, and may, by the proper means, be rendered 

 entirely so. 



243. DIAMAGNETISM. If a needle of 

 What is said j ron be hung, by a thread, between the 



of diamagnet- J 



ism? poles of a horse-shoe magnet, it immedi- 



ately turns, so that one of its ends points 

 to the north pole, and the other to the south. This 

 is also a consequence of induced magnetism, as ex- 

 plained in the preceding paragraph. The metal nickel, 

 oxygen gas, and many other substances, both solid, 

 liquid, and gaseous, are similarly attracted by the 

 poles of a magnet, though in a much less degree. All 

 bodies which are not attracted are repelled, and if sus- 

 pended between the poles, turn so as to bring their ex- 

 tremities as far away from the poles as is possible. 

 The former class are called magnetic, and the latter 

 diamagnetic bodies. To show the phenomena of at- 

 traction and repulsion with gases and liquids, the mate- 

 rials are inclosed in tubes or bulbs. In the case of most 

 substances, excepting iron, these effects can only be at- 



