CHANGE OF DIMENSIONS BY MAGNETIZATION. 



93 



In weak fields, the curves nearly coincide with each other. The 

 field of maximum elongation slightly increases with the circular, 

 and the amount of the elongation, after reaching a maximum, begins 

 to decrease with further increase of the circular field. Tliough 

 Bid well did not observe this point, the present experiment agrees 

 quite well with his result. 



16. So far the experiments made on the tubes of nickel, 

 steel and iron show that the effect of circular field on the change 

 of length by longitudinal magnetization is of the same nature 

 as the effect of longitudinal field on the change of length by 

 circular masrnetization. 



From the results of the change of length by longitudinal 

 and circular magnetizations, the change of volume by magne- 

 tization can easily be calculated, provided we assume the material 

 to be isotropic, as was already done by Bidwell. If ti and v 

 represent these two dilatations respectively, the volume change a 

 is given by the formula (t=u +2i\ 



Assuming the isotropy of our specimens, we find the 

 calculation leads to the followins; results : 



TABLE VIII. 



