114 Prof. Waltenhofen on an anomalous Magnetizing of Iron. 



strength of the magnet due to previous magnetism*, and the 

 relations between torsion and magnetism f. 



An experiment of the simplest kind, and which may be regarded 

 as an eocperimentum crucis against the theory of the two fluids, is 

 to be found in my observation of the anomalous magnetizing of 

 iron, which forms the subject of this communication. 



In examining the residual magnetism which is displayed by 

 electromagnetic masses of iron after the stoppage of the magne- 

 tizing current, I have observed that it is nowise indifferent 

 whether the circuit be broken suddenly or whether the intensity 

 of the current be previously diminished by interposing resist- 

 ance, and gradually, when it has become nearly zero, altogether 

 stopped. 



In the former case the residual magnetism is always much less 

 than in the latter. 



I have particularly noticed this difference in thick cores of iron. 

 In such I have not seldom observed that, on the sadden breaking 

 of the current, there was residual magnetism of an opposite cha- 

 racter to the temporary magnetism which had disappeared, a 

 phenomenon which may be designated " anomalous magneti- 

 zing." These phenomena cannot be looked upon as secondary 

 actions of induced currents, inasmuch as the opening currents 

 are in the same direction with the primary currents, and so, on 

 the contrary, can only go to increase the residual -magnetism. 

 As in support of this view I refer particularly to the explana- 

 tions with which Magnusf and Helmholtz§ have discussed the 

 behaviour of electromagnetized masses of iron on breaking the 

 circuit, it does not seem to me to be necessary to dwell upon this 

 part of the question. 



I think, moreover, that these phenomena find an explanation 

 equally simple and satisfactory if we abide strictly by the sup- 

 position that in the movements of the magnetic particles, besides 

 the tendency to return to the original position of equilibrium, 

 there is also a certain resistance due to friction. 



Thus, if we suppose the magnetic particles to be displaced by 

 a magnetizing agency, it is clear, in accordance with the above, 

 that on the gradual diminution and removal of this force they 

 must assume other positions of rest than when it is suddenly 

 removed. 



In the former case, in which the molecules are allowed to move 

 slowly, the resistance due to friction prevents a complete return 



* Wiedemann, Pogg. Ann. vols. e. and cvi. ; also Waltenhofen's obser- 

 vations on the Electromagnetism of Steel. 



t Matteucci, Wertheim, and Wiedemann. See the "Galvanism and 

 Electromagnetism " of the latter. 



X Pogg. Ann. vol. xlviii. § Ibid. vol. lxxxiii. 



