160 ON MAGNETISM. 



In the mean time, we prefer the theory of Article 

 63 to Poisson's theory ; inasmuch as it gives distinct 

 indications of the connexion between the arrangement 

 of the masses of iron and the laws (irrespective of mag- 

 nitude) of the compass- disturbance ; depending so 

 clearly on general principles of the translation of mag- 

 netism by the influence of external magnetic forces 

 that they will never be materially modified. On these 

 points, Poisson's generalities give no assistance. 



72. Complexity introduced, by induction, into the 

 laws of the action of magnets upon each other. 



We may regard a magnet as consisting throughout 

 of two materials : one the ferruginous part, of which the 

 magnetism is liable to be shifted by the action of an 

 external magnet : the other the magnetizable steel, 

 properly so called, in which the magnetism is fixed. 

 This produces (among other complications) a difference 

 between the attractive and the repulsive powers. For, 

 if the red pole of the first magnet is presented to the 

 blue pole of the second, and strong magnetic attraction 

 takes place, the red pole induces blue magnetism in the 

 adjacent ferruginous part of the second magnet, and the 

 blue pole induces red magnetism in the adjacent ferru- 

 ginous part of the first magnet, and the total attraction 

 is increased. But if the red pole of the first is presented 

 to the red pole of the second, and there is consequent 

 repulsion ; each red pole induces blue magnetism in the 

 adjacent ferruginous part of the other magnet, and 



