460 K. Honda, S. Shimizu, and S. Kusakabe on Change of 



of elasticity amounting to about -J per cent. J. S. Stevens- 

 and H. G. Dorsey * used the method of flexure, and applied 

 the interference-fringes to measure the amount of depression. 

 The effect of magnetization upon a loaded iron and steel bar 

 was found to be very small ; it showed a minute increase 

 of the modulus of elasticity by about 3-^- per cent, for the 

 strongest current used. In the next year, Stevens measured 

 the magnetic elongation of steel wires under several loadings 

 and found an increase of elasticity. Lately, Tangl f published 

 his results on the same subject. He made use of the prin- 

 ciple that the moment of a bifilar suspension increases with 

 tension applied to its lower end. Besides iron, he also 

 examined nickel wires. In fields ranging from 200 to 480 

 C.G.s. units the maximum increase of the modulus of elasticity 

 amounted to about 1 per cent, for iron and nickel. 



All of these experiments show that magnetization increases 

 slightly the modulus of elasticity in iron and nickel, and that 

 the change increases with magnetizing force, but its law is 

 not clearly brought out. 



2. The method of measurement in our experiment was 

 similar to that of Stevens and Dorsey, as shown in fig. 1. 



Fig. 1. 



R 



.rpo-Ti 



£ 



IB 



-M 



ffi. 



A and B are two magnetizing coils of the same dimensions, 

 which rested horizontally in a coaxial line. F G is a stout 

 brass rod of rectangular section extending between two 

 fulcrums ; it is also supported at the middle point by another 

 fulcrum. The coils can therefore be moved independently of 

 the bar. L M is a rod to be tested placed in the axial line 



* J. S. Stevens and H. G. Dorsev, Phys. Rev. [2] ix. p. 116 (1899) ; 

 Phys. Rev. [2] xi. p. 95 (1900) ; ZeiUchr. ii. p. 682 (1900). 

 t Tangl, 'Ann. de Phys. vi. p. 34 (1901). 



