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THE POPULAR SCIENCE MONTHLY. 



yield up every distinctive feature of tlie magnet, is successfully 

 opposed by the hardness of the steel bar. 



The lines are called lines of magnetic force, and the area over 

 which their influence is felt is known as the magnetic field. If a 

 compass-needle, suspended by a silk thread and free to move in 

 any plane, be brought into this field, it will assume a direction 





^ — - 





n 



\ 



yt 



t 









/ li \ 



Fig. 1.— The Steel Bab-Magnet. J\"and .S', poles ; n n, neutral ground. 



parallel to the lines of force, as at e, e', e" . . . e^. The strength of 

 the field, and hence the force that tends to give the needle steadi- 

 ness and direction, varies greatly at different points — at e it is 

 powerful, at e'" feeble. 



If two magnets similar to that of Fig. 1 be brought into prox- 

 imity, so that poles of the same name touch, they will repel each 

 other; if, on the other hand, the north pole of one be approached 

 to the south pole of the other, both bars, as if instinct with life. 



