68 Prof. G. Wiedemann's Magnetic Researches. 



to a given magnetizing force is always greater with decreasing 

 forces than with increasing forces. 



Here, also, there prevails then a complete analogy to the me- 

 chanical behaviour under torsion produced by increasing and 

 decreasing torsional forces. 



§7. 



The gradual accommodation of the molecules upon repeated 

 torsion within certain limits, described in the foregoing pages, 

 as recognized by magnetic behaviour, in which the deflec- 

 tions with the same torsion increase at first, agrees with the 

 result of my former experiments *, that the permanent torsions 

 of a wire, upon repeated temporary twistings of the same up 

 to a certain limit, and also in the same way upon repeated 

 action of the same torsional force, increases gradually up to 

 a maximum. This behaviour shows clearly that the molecules 

 in the deformed wire are only carried gradually from the posi- 

 tion of equilibrium corresponding to the zero into that which 

 corresponds to the deformation. The same holds good of the 

 action of magnetic forces tending to rotate the molecules. 

 Here, also, as the second Table, § 6, shows, the permanent 

 moment increases gradually up to a certain maximum, upon 

 repeated temporary magnetization up to a certain limit. 



In the same way, as the above experiments show, an iron 

 bar only attains, after the repeated action of a given mag- 

 netizing force, the maximum magnetic moment corresponding 

 thereto. 



This last-mentioned behaviour has already been observed 

 by Queteletf in repeatedly rubbing steel needles with a 

 magnet, and by Hermann and Scholz upon repeated contact 

 with the pole of a steel magnet, and similarly by Bouty f and 

 Frommef upon the repeated introduction of iron bars into 

 magnetizing spirals traversed by a constant current J. In 

 this last method, the separate portions of the bars are succes- 

 sively exposed to the magnetizing forces of different intensity 

 at the different points of the spiral, and thus the position of 

 the molecules of the bars already taken up at one point may 

 assist the adjustment of the molecules at other points 

 in the subsequent introduction into the spiral, or rubbing, 

 and thus explain the increase of the permanent moments. 



* G. Wiedemann, Wied. Ann. mi. p. 495 (1879). 



f On the literature of the subject, see G. Wiedemann, Elect, iii. p. 442, &c. 



-\ I have formerly obtained a series of results on the magnetization and 

 demagnetization of iron and steel bars by the same method. Experi- 

 ments by the method now employed with constant distribution of the 

 magnetizing forces give (qualitatively) the same results. 



