ELEMENTARY MAGNETISM. 359 



ishes, and the repulsion of like poles is sensibly equal 

 to the attraction of unlike ones. 



I dwell thus long on elementary principles, because 

 they are of the first importance, and it is the tempta- 

 tion of this age of unhealthy cramming to neglect 

 them. Now follow me a little farther. In examining 

 the distribution of magnetism in your strip of steel 

 you raised the needle slowly from bottom to top, and 

 found what we called a neutral point at the centre. 

 Now does the magnet really exert no influence on the 

 pole presented to its centre? Let us see. 



Let s N, fig. 11, be our magnet, and let n represent 

 a particle of north magnetism placed exactly opposite 

 the middle of the magnet. Of course this is an im- 



I -IN 



aginary case, as you can never in reality thus detach 

 your north magnetism from its neighbour. But sup- 

 posing us to have done so, what would be the action of 

 the two poles of the magnet on n? Your reply will of 

 course be that the pole s attracts n while the pole N 

 repels it. Let the magnitude and direction of the 

 attraction be expressed by the line n m, and the mag- 

 nitude and direction of the repulsion by the line n o. 

 Now, the particle n being equally distant from s and x, 

 the line n o, expressing the repulsion, will be equal to 

 m n, which expresses the attraction. Acted upon by 

 two such forces, the particle n must evidently move in 

 the direction n p, exactly, midway between m n and n o. 

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