l; EStiARCHES ON MAGNETOSTRICTION. 



385 



We now use the numbers in Table 2 and calculate the strain Hue 

 to magnetization ; we thus obtain 



As calculated from the strain effect, the change of magnetization 

 due to longitudinal pull reaches a minimum in a critical held as 

 already verified by experiment ; there is some discrepancy in the 

 actual numbers, hut the quality of the change does not show any 

 material différence. The change of length in nickel as calculated from 

 the stress effect fairly agrees with the observed values, except in 

 strong fields, where the deviation becomes apparent. Of the two sets 

 oi /.:'. the one derived from the effects of smaller stress gives results 

 which approach the experimental number at least in quality. The 

 agreement between theory and experiment would perhaps be closer, 

 could we measure the change of intensify by still smaller loading ; or 

 better still from effects of small longitudinal compression. Adopting 

 the numbers obtained from the stress effect, the change of volume by 

 magnetization ought to lie very small. The discrepancy between 

 theory mid experiment lies in the sign ; theory gives increase of volume 

 instead of diminution :is in the actual case. But considering the 

 minuteness of the change and the experimental errors which enter in 

 the determination of/»;' and />,", we can not say that the discrepancy is 

 of a serious nature. 



