390 ir SAGAOKA AND K. HONDA; 



(il) (Theory mihI Experiment) By the apj)lication of ;i small consta.nl 

 longitudinal pull, there is decrease of magnetization in nickel 



till it reaches a minimum in moderate field, thence to increase 

 gradually, but not to such a degree as to reach a value greater 

 than in the nnstretched condition. 

 //. Strains caused la/ magnetization calculated from tlie effects of' 

 stress. 



(a) (Theory and Experiment) Magnetization produces increase 

 of volume in iron. (But the value assigned by theory is about 

 15 times greater than the observed result). 



(b) (Theory) Magnetization produces a small increase of volume in 

 nickel (to a degree which is quite within the expérimental 



error). 



(Experiment) Magnetization produces diminution of volume. 



(c) (Theory and Experiment) Magnetization produces increase of 

 length in iron, till it reaches a maximum in a critical field 

 (J3=30), thence to diminish gradually with increasing field. 



(d) (Theory and Experiment) Magnetization produces continuous 

 diminution of length in nickel. 



Experiments show that the coefficients ¥ and k" are complicated 

 functions of the strain, but Kirchhoff's theory makes the change of 

 magnetization simply proportional to the strain. Strictly speaking 

 Kirchhoff's theory is a rough approximation, and will perhaps only 

 hold when the strain is infinitely small ; we can not therefore, expect 

 that such a theory will explain all the relations between the strains 

 caused by magnetization and the effects of stress on magnetization in 

 all their qualitative and quantitative details. Tn the present 

 investigation, we have taken care to measure such effects as will be 

 most conformable to the theory. We have thus found out that, ex- 

 cepting the theoretical deduction as to the effect of hydrostatic 



