310 ANALOGY OF MAGNETISM SECT. XXX. 



tremely feeble, since the iron is easily rendered mag- 

 netic by induction, and as easily loses its magnetism ; 

 whereas in steel the coercive force is extremely ener- 

 getic, 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 experiences in 

 electrics. At every step the analogy between magnet- 

 ism and electricity becomes more striking. The agency 

 of attraction and repulsion is common to both; the pos- 

 itive 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 repul- 

 sion, and between unlike powers there is attraction. 

 Each of these four forces is capable of acting most ener- 

 getically 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 polar- 

 ities, 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 simi- 

 lar to electrical induction. There is even a correspond- 

 ence between the fracture of a magnet and that of an 

 electric conductor ; for if an oblong conductor be elec- 

 trified by induction, its two extremities will have opposite 

 electricities ; and if in that state it be divided across the 

 middle, the two portions, when removed to a distance 

 from one another, will each retain the electricity that 

 has been induced upon it. The analogy, however, does 

 not extend to transference. A body may transfer a re- 



