RESEARCHES ON MAGNETOSTRICTION. 379 



These equations give 



(« +2/3) r m 



2üT(l + 30) ~~ 2Z0 ' 



Similarly we obtain 



The elongation in the direction of magnetization i 



o / ÏÏ 2 ( _ 7 , A" , (fc-fc') 



; the Poisson ratio is - 

 prismatic body 



Supposing that the Poisson ratio is -— — , or 6 = —-j-, we find for a 



Corresponding formulae for the ovoid are, according to Cantöne, 



._ ol _ P / k—V W_ 



<? y P /_ , :-î(7>- 7Q A" 



Comparing the formula' (a) (/>) (c) (J), we und that the change of 

 volume is the same for the ovoid as for the prismatic body ; 

 the difference in the length change is equal to ~ ,. , 0( y^ 5 Dem g 

 slightly greater for the prismatic body than for the ovoid. 



