12 OX MAGNETISM. 



between magnetisms of similar character and attraction 

 between magnetisms of dissimilar character. 



An additional result, of some importance, is gained 

 by holding the hand-magnet in a vertical direction and 

 bringing it sideways towards one end of the needle. 

 It will be found that the energy of the attraction (or 

 repulsion, as the case may be) varies as the hand- 

 magnet is moved up and down; and that it is greatest 

 when a part of the hand -magnet near to its end but 

 not at its end (distant from it perhaps by -^ of the 

 magnet's whole length) is nearest to the needle. This 

 suggests the idea that the whole of the magnetism 

 peculiar to that end of the magnet is collected into 

 that one point : and that point is called a " Pole." But 

 in fact it is found that, in varying the experiment, no 

 point can be fixed on as strictly corresponding to this 

 idea of a pole ; still the language and the idea are so 

 convenient that we shall make use of them, in general 

 description, and even in some investigations. 



It is easily found that the effect of one magnet may 

 be neutralized by that of another magnet. Thus, if one 

 magnet be below the needle, a similar magnet above 

 the needle with its poles in opposite positions will 

 neutralize it. The reader will have no difficulty in 

 varying this experiment, so as to make it applicable 

 to the other cases of magnetic disturbance. 



If a horse-shoe magnet be held in a vertical position, 

 and if its ends be separately presented sideways to a 

 suspended magnet, it will be found that they possess 



