304 Dr. C. Fromme on the Magnetism of Steel Bars. 



and my results will be found not merely not contradictory, 

 but probably mutually complementary. 



For reasons easily conceivable, which I need not further 



discuss, it cannot well be assumed that the ratio ,} continues 



to diminish till it arrives at zero ; much rather it is not im- 

 probable that, as the magnetizing force goes on increasing, the 

 ratio begins to rise again. M. Bouty, however, worked with 

 very thin, while I worked with tolerably thick steel bars ; and 

 hence it really follows that in his, in comparison with my ob- 

 servations, much greater magnetizing forces were in play. At 

 all events the subject is well deserving of further examina- 

 tion ; and I shall not delay commencing experiments for that 

 purpose. 



§ 14. In § 9 the proposition is advanced that a force of de- 

 terminate intensity cannot generate residual magnetism beyond 

 a determinate limit. Taken rigorously, this is not quite correct 

 — at least, not in the sense in which it was there understood ; 

 for if, by repeated action of a constant force, a steel bar be 

 brought to the corresponding maximum of its residual mag- 

 netism, then loses a portion by concussions, or even by merely 

 lying at rest, and thus by the action of time, and afterwards 

 the same force be again applied, the residual magnetism now 

 increases beyond the previous limit. 



If the same process be again repeated several times, a limit 

 must finally be reached which will not be exceeded even by 

 further losses and fresh magnetization. This value only of the 

 residual moment can be designated the proper moment of sa- 

 turation of the force in question. 



It is self-evident, and confirmed also by my experiments, 

 that where a loss of residual magnetism has occurred in a bar 

 which had been previously saturated by a force P, even a force 

 p, which before, with a maximum attained, could no more 

 than P itself produce an augmentation, can raise the diminished 

 residual moment, and, if the intensity be sufficient, bring it 

 back to the maximum corresponding to the force P. 



§ 15. We have hitherto considered only one part of what 

 takes place in the repeated magnetization of a steel bar by a 

 constant force, namely the variation of the residual magnetism. 

 But similar questions to those respecting the residual, can now 

 be put concerning the temporary magnetism. Here three 

 cases are to be distinguished. 



The first, simplest, is that of repeated magnetization by the 

 same current, which, however, has never previously acted on 

 the rod (§ 9). The question is: — Does the temporary magne- 



