THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



SEPTEMBER 1898. 



XXVI. On Magnetostriction. By H. Nagaoka and 

 K. Honda, Imperial University, Tokyo *. 



[Plates I. & II.] 



THE object of the present investigation is two-fold : 

 firstly to determine the effect of hydrostatic pressure 

 on the magnetization of iron and nickel and to find whether 

 there exist reciprocal relations between the effects of com- 

 pression and the volume-change of ferromagnetics by magne- 

 tization ; secondly, to examine Kirchhoff's f theory of mag- 

 netostriction from measurement of strains produced by 

 magnetization and from the effects of stress on the magnetiza- 

 tion of iron and nickel. 



Both experiment and theory show that physical changes 

 are mostly reciprocal. In magnetism, this fact is markedly 

 brought out by the mutual relations between twist and 

 magnetization J, as well as by the change of length caused 

 by magnetization and the effect of longitudinal pull applied 

 to the magnetized wire. Theoretical exposition of these 

 facts was given by J. J. Thomson § ; by applying similar 

 reasoning to the effect of hydrostatic pressure on magnetiza- 

 tion, we can show that the change of volume accompanying 



* Communicated bv the Authors. 



t Kirchhoff, Sitzber. d. k. Acad. d. Wiss. zu Berlin, p. 137 (1884) ; 

 Wied. Ann. vol. xxiv. p. 52 ; Gesammelte Abhcmdlungen, Nachtrag, p. 91, 

 Leipzig (1891) ; see also Pearson's 'History of Elasticity/ vol. ii. p. 105, 

 §§ 1319-1321. 



X See Wiedemann's Electricitat, Bd. iii. pp. 767-814 (dritte Auflage). 



§ J.J. Thomson, ' Application of Dynamics to Physics and Chemistry ' 

 (1888). 



Phil Mag. S. 5, Vol. 46. No. 280. Sept. 1898. U 



