2 ART. 4. — K. HONDA AND T. TERADA. 



stants by magnetization, the right order of properly applying the 

 stress and the field was inverted. In some experiments/^' the 

 effect of tension on the magnetic elongation was observed, and 

 the change of the modiihis of elasticity was deduced on the as- 

 sumjDtion that the effect was due to the change of elasticity by 

 magnetization. The acoustical methodf used by several experi- 

 menters is also an indirect one, and unsuitable for any accurate 

 determinations. In H. Rensing's experimentj, Kundt's tube was 

 used ; but the field in which tlie bar was placed, was far from 

 being uniform. 



Our present experiments were undertaken with the main 

 object of measuring the change of elastic constants of the same 

 specimen by the direct as well as the indirect method and com- 

 j)aring the results thus obtained : the specimen to be tested being 

 placed in a nearly uniform field. 



If Ç be the length or the angle of twist of the specimen, S 

 the applied tension or couple respectively, and H the magnetic 

 field, we have the relation 



iii)-jL(m (!) 



OS J ~ DS V)H) ^ ^ 





provided the change is independent of the order of applying the 

 field and the stress. Thence we have 





If M be the modulus of elasticity or that of the rigidity respec- 

 tively, 



*) Rock, Wie.l. Ann. 54, 442, 1895; Phil. Mag. (5) .39, 548, 1895. K. Tangl, Ann. der 

 riiys. 6, 34, 1901. K. ITonda :uurS. Sliimizu, loc. cit. 



t) \V:irtm:mn, Ann. de Chim. et de Pliys. 24, 360, 1843. Treves, C. R. 67, 321, 1868; 

 Archives des Soc. Nat. N. S. 3», 74, 1868. Manrain, C. R., 121, 248, 1895. 



%) Rensing, Ann. der Pliys. 14, 363, 1904. .: 



