388 



ii. naoaoka and k. huxda 



with experiment, although the actual number« are somewhat 

 different, as will be seen from the lasl column 



[f we now make use of the experimental result that the effect 

 of hydrostatic pressure is negligibly small compared with that of the 

 longitudinal, we obtain the following- values of k'= — k" 



Tal »le. 4. 



The numbers found above differ widely from those calculated 

 from the strains due to magnetization, but the general character of the 

 coefficient // is similar. Using the values of // in Table I, we find 

 that the change of length given in the -n-d column fairly agrees with 

 the experimental determination in the 4th column. The field of 

 maximum elongation (H=30) given by calculation agrees pretty well 

 with the actual result. 



According to Kirchhoff's theory, there is always increase of 

 volume with increasing field, but the calculated result is about 

 15 times greater than the experimental numbers. Thus, the theoretical 

 result as regards the change of volume agrees only in quality. 



From experiments on the effect of twist on a circularly magnetiz- 

 ed wire, Drude i; found that in low field / /' = 4tt//' = 4x 10'; here we 



1). Drude, Wied. Ann. 63 p. s, 1897 



