4 AKT. 12.— K. ONDA, S. SHIMIZU, ÄND S. KÜSAKABE : 



method makes ii.se of the acoustic phenomena and can not be used for 

 accurate determinations. 



The second is the method of elonjjation. Since, the elonfjation 

 due to the cliange of elasticity is only a small fraction of the total 

 elongation, this method is only suitable for the accurate measurement 

 of the effect in question, when a differential method is applicable. 

 Unfortunately this is not the case in the present instance ; for if we 

 first stretch the wire by a tension and then magnetize it, there is 

 always magnetic elongation which is far greater than that due to the 

 change of elasticity. 



We may, however, modify the measurement in the following 

 way, as l^idwell and others have done. The wire is first brought 

 under tension, and then the mao-netic elono^ation in different fields is 

 determined. This process is repeated with several loadings. From 

 these sets of observation, we may decide the question. — How is the 

 elasticity of a ferromagnetic wire affected by magnetization ? 



Let E' and E be the modulii of elasticity within and without the 

 magnetizing field, and e' and e the magnetic elongations per unit of 

 length w'ith and without the tension, respectively. We first load the 

 wire with the tension T per square centimeters, and then magnetize it; 

 the total elongation in 1cm will be 



Xext, changing the order of operations, we first magnetize the wire 

 and tlien stretch it ; then elongation will be 



e+(l + e)—. 



If the elongation is independent of the order of operations, we get, 

 neglecting small quantities, 



putting E' — E=JE, we have 



