380 FRAGMENTS OF SCIENCE 



particles of magnetism, we place a little magnetic needle, 

 containing both north and south magnetism, opposite the 

 magnetic equator, its south pole being urged along n q, 

 and its north along n p, the little needle will be com- 

 pelled to set itself parallel to the magnet s N. Make 

 the experiment, and satisfy yourselves that this is a true 

 deduction. 



Substitute for your magnetic needle a bit of iron wire, 

 devoid of permanent magnetism, and it will set itself ex- 

 actly as the needle does. Acted upon by the magnet, the 

 wire, as you know, becomes a magnet and behaves as 

 such; it will turn its north pole toward p, and south pole 

 toward q, just like the needle. 



But supposing you shift the position of your particle 

 of north magnetism, and bring it nearer to one end of 

 your magnet than to the other; the forces acting on the 

 particle are no longer equal; the nearest pole of the mag- 

 net will act more powerfully on the particle than the more 

 distant one. Let s N, Fig. 12, be the magnet, and n the 

 particle of north magnetism, in its new position. It is 

 repelled by N, and attracted by s. Let the repulsion be 

 represented in magnitude and direction by the line n o, 

 and the attraction by the shorter line n m. The resultant 

 of these two forces will be found by completing the par- 

 allelogram m n o p, and drawing its diagonal n p. Along 

 n p, then, a particle of north magnetism would be urged 

 by the simultaneous action of s and N. Substituting a 

 particle of south magnetism for n, the same reasoning 

 would lead to the conclusion that the particle would be 

 urged along n q. If we place at n a short magnetic nee- 

 dle, its north pole will be urged along n p, its south pole 

 along n q, the only position possible to the needle, thus 



