126 ELEMENTS OF SCIENCE 



contrary, be repelled by the other pole, or end, X, which 

 was first presented to the needle. 



It would thus seem, judging from the phenomena of 

 the pith balls before noted,* that there are two kinds of 

 magnetism, as there are two kinds of electricity, and this 

 may be made certain by the following simple experiment. 

 Take two needles, the ends of which we may distinguish 

 as A and B. Magnetise them by rubbing several 

 times from the middle of each towards the points, but 

 towards the points A and A with one end of the horse- 

 shoe magnet, and towards the points B and B by its 

 other end. Then evidently the A poles of the two 

 needles will have gained one kind of magnetism, and 

 their B poles the other kind. Thereupon it will be 

 found that both their A and B poles repel each other, 

 while the A pole of each will attract the B pole of the 

 other needle and vice versd. Therefore of the two kinds 

 of magnetism like the two kinds of electricity it may 

 be said that like repels like but attracts unlike. 



We have before spoken f of the polarity of light, but 

 polarity is thus especially manifest in magnets and by 

 means of magnetism. The polarity of magnetism is like 

 that of electricity, in that one cannot exist without the 

 existence of the other in its neighbourhood. But two 

 bodies can be in different electrical conditions, each 

 having only one kind of electricity, as e.g., in the silk 

 and the glass rod. Such, however, is not the case with 

 magnetism, since every magnetic body must have, in 

 itself, both of the magnetic polarities. However small 

 the fragments into which a magnet may be broken, 

 each fragment will always possess both kinds of mag- 

 netism and have two poles and not one only. 



* See ante, p. 119. f See ante, p. 113. 



