294 Dr. C. Fromme on the Magnetism of Steel Rars. 



ration with residual magnetism corresponding to this force), a 

 smaller force p cannot change it. 



To all forces from zero to P inclusive, a steel bar brought to 

 the boundary value of residual magnetism corresponding to the 

 force P behaves like an iron bar icithout any coercive force. 



This proposition may also be expressed thus : — 



For each permanent moment of a steel bar there exist, from 

 zero upward, a series of magnetizing forces, in relation to which 

 this bar p>ossesses the properties of an iron bar, or (taking as a 

 basis the idea of molecular magnets capable of rotation, and 

 assuming that in a bar entirely of soft iron the molecular 

 magnets have only one position of equilibrium, but in a steel 

 bar innumerable positions of equilibrium), expressed in the 

 language of mechanics : — 



Each of the innumerable positions of equilibrium of the mole- 

 cular magnets of steel is stable for a certain range of deforming 

 forces. The less the arrangement of the molecular magnets de- 

 viates from the direction of the forces, the more extended is the 

 ■range of the forces that can be employed. 



Although a proof of Maxwell's theory cannot hence be de- 

 duced, an argument in favour of it can ; for if even for the 

 greatest deformations the molecular magnets preserve the sta- 

 bility of their equilibrium, provided only that their positions 

 of equilibrium correspond to an extremely powerful permanent 

 magnetism, one cannot see why the arrangement of the mole- 

 cules which corresponds to the unmagnetic state should not 

 also exhibit, for certain very feeble forces, a stability of the 

 positions of equilibrium. 



But, further, it is evident that, for a steel bar which is not 

 entirely freed from permanent magnetism, in proportion to the 

 quantity of this must also the range of the forces which leave 

 no residual magnetism behind be more extensive. Probably 

 it was the considerable permanent magnetism possessed by I. 5 

 in the experiments described in § § 6 and 7 that occasioned the 

 greater value of the argument K at which residual magnetism 

 first entered. See the remark in § 7. 



]^ow the following is what takes place in the repeated mag- 

 netization of a steel bar by a constant magnetizing force P :- 

 The first impulse produces a residual moment M x ; this cor- 

 responds to a certain force (jh < P) as the moment of satura- 

 tion. The second impulse increases the residual moment by 

 M 2 — M 1? M 2 corresponding to a force p 2 as moment of satura- 

 tion ; p 2 >pi. ■ 



§ 10. The fact that a steel bar with great coercive force may, 

 under some circumstances, behave like an iron bar without any 

 coercive force appeared to me so important, that I resolved to 



