CHANGE OF ELASTICITY BY MAGNETIZATION. 3 



Stevens and H. G. Dorse\" used the method of pressure and applied 

 the interference frin,o-es to measure the amount of depression. The 

 effect of magnetization upon a loaded iron or steel bar was found to 

 "be very small ; it showed a minute increase of elasticity, amounting 

 only t(^ ^% for the strongest current used. The effect also increased 

 with maofnetizino- current. In the next year, Stevens measured the 

 niao^netic elono^ation of steel wires under different tensions, and 

 ascribed the change of elongation to that of elasticity by magnetization, 

 as l^rackett did. The result was an increase nearly proportional to 

 the magnetizing force. Lately K. Tangl'-^ has published his results on 

 the same subject. He made use of the principle that the moment of 

 n biülar suspension increases with tension applied to its lower end. 

 B}^ magnetizing the wire under constant tension, he measured the 

 amount of the magnetic elongation. The tension was, then, so varied 

 that the wire returned to its initial length. The ratio of the tension 

 so varied to the magnetic elongation was taken as proportional to the 

 increase in the modulus of elasticity in that field. ]>esides iron, he 

 also examined nickel wires which showed a small increase of elasticity. 

 In fields rano^inç^ from 200 to 480 C. G. S. units, the maximum 

 increase amounted to about 1.02% for iron as well as for nickel. He 

 also investigated the effect of tension, but the result does not seem to 

 be satisfactory. 



All of these experiments show that the magnetization increases 

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

 change increases with the magnetizing force, but its law is not clearly 

 brought out. 



2. Different methods, by which previous experimenters de- 

 termined the said effect may be grouped under three heads. The first 



1) Stevens and Dorsey, Phy. Rev. (2) 9, lid, 1899; Phy. Eev. (2) \\^ 95, 1900; Phy. 

 Zeitschr. 2, 682, 1900. 



2) Tangl, Ann. der Phys. 6, 34, 1901. 



