SECT, xxx.] TWO MAGNETIC POLES. 353 



be some coercive force analogous to friction, which arrests 

 the particles of both fluids, so as first to oppose their 

 separation, and then to prevent their reunion. In soft iron 

 the coercive force is either wanting or extremely feeble, 

 since the iron is easily rendered magnetic by induction, 

 and as easily loses its magnetism ; whereas in steel the 

 coercive force is extremely energetic, because it prevents 

 the steel from acquiring the magnetic properties rapidly, 

 and entirely hinders it from losing them when acquired. 

 The feebleness of the coercive force in iron, and its energy 

 in steel, with regard to the magnetic fluids, is perfectly 

 analogous to the facility of transmission afforded to the 

 electric fluid by non-electrics, and the resistance it expe- 

 riences in electrics. At every step the analogy between 

 magnetism and electricity becomes more striking. The 

 agency of attraction and repulsion is common to both ; the 

 positive and negative electricities are similar to the northern 

 and southern polarities, and are governed by the same laws, 

 namely, that between like powers there is repulsion, and 

 between unlike powers there is attraction. Each of these 

 four forces is capable of acting most energetically when 

 alone; but, as the electric equilibrium is restored by the 

 union of the two electric states, and magnetic neutrality by 

 the combination of the two polarities, they respectively 

 neutralize each other when joined. All these forces vary 

 inversely as the squares of the distances, and consequently 

 come under the same mechanical laws. A like analogy 

 extends to magnetic and electrical induction. Iron and 

 steel are in a state of equilibrium when the two magnetic 

 polarities conceived to reside in them are equally diffused 

 throughout the whole mass, so that they are altogether 

 neutral. But this equilibrium is immediately disturbed on 

 the approach of the pole of a magnet, which by induction 

 transfers one kind of polarity to one end of the iron or steel 

 bar, and the opposite kind to the other effects exactly 

 similar to electrical induction. There is even a correspon- 



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