4 ART. 8.— H. NAGAOKA AND K. HONDA: 



as|)ect, as ior the length cliange, and tlie sense of tAvist is the same 

 as that of iron in weak fields. 



A singular characteristic of magnetostriction is its reciprocity 

 with the eftect of stress on the maj^netization of diiterent ferromaofne- 

 tic substances. In the present instance, we have tin*ned our attention 

 especially to cobalt and nickel steels. As will Ije expected from the 

 nature of the length change, the former metal is characterized by the 

 existence of a minimum point closely analogous to that bearing the 

 name of ^' illari for iron, while with the latter, the eftect of the longi- 

 tudinal pull always results in an increase of magnetization. The 

 parallel statements giving the correlation between the magnetization 

 and the torsion, first introduced by G. Wiedemann, can thus be ex- 

 tended to other effects of stress and the strain resultin«: from the 



a 



maofnetization. 



The present paper is limited to the mere description of the ex- 

 perimental investigation, the theoretical discussion being reserved for 

 future consideration. 



§ 2. Intensity of Magnetization. 



In all of our measurements, we noticed the chano^e of dimensions 

 by magnetization and the strength of the field H (H = H' — NI, where 

 H' is the external field, X the demagnetizing factor, and I the inten- 

 sity of magnetization). It will therefore not be out of place to make 

 a digression on the magnetization of the ferromagnetic substances 

 here examined, in order to enable us to examine the various changes 

 considered as functions of the intensity of magnetization. 



The followinof table o:ives the dimensions as well as the demas^ne- 

 tizing factor N of the ovoids examined in the present experiments. 

 <( : Semi-minor axis of the ovoid. 

 c : Semi-axis of rotation of the ovoid. 



