EFFECT OP STRESS ON MAÜNP:T1ZAT10N. OÔ 



By a direct method, Dr. S. Sano obtained the relation 



dl . 7(1-2.7) . 27T (ijxlH-') ,. 



de 



un 



where x„ is ;i term in the expression of susceptibility, whicli 

 is independent of tlie strain. Since I = xJF, Sano's equation 

 practically coincides with Gans's. For the change of elasticity, 

 Dr. Sano obtained 



which is practically the same as Heydweiller's equation, but 

 different from Gans's by a term not negligibly small in Aveak 



fields. The above equation was obtained independently of the 



Oc 

 relation for g^r • As to the effect of twist. Dr. Sano obtained 



an equation, which can be transformed into (12). 



Thus far, the relations for r-^, given by Heydweiller, Gans, 

 Kolâcêk and Sano all agree with one another in the first im- 

 portant term -^yr- Relation (1) given by J.J. Thomson does not 

 differ in reality from others. Relation (13) given by Cantone 

 also coincides with others in the first term, provided x is in- 

 dependent of H. The second term 7(1-2^)/^ in (8) and (10) 

 may be neglected for the first approximation ; the third term in 

 relation (10), which becomes important in weak fields is properly 

 to be added. 



The relations for -r-fr- given bv Heydweiller, Gans and Sano 



' 0^7 



also agree with each other in the first term — r-rpr- Gans's differs 



principally from the others by a term not generally small in 



weak fields. 



As reojards the relation for -^i-, Kolâcêk's and Sano's coin- 



cide with each other. Thomson's relation (6) also does not difier 



