386 



H. STAGA0KA AM> K. HONDA ; 



It must not be forgotten that these numbers h\ k" are functions 

 of the strain caused by mechanical action on nickel. Taking Prof. 

 Swing's experiments on the magnetization of nickel under various 

 loadings, we find the following values of —k' on the supposition thai 



The above values will probably not be far from those obtained by 

 actual determination. The constants h' and k" are thus functions of 

 the strain of the magnetized body. In nickel— k' diminishes as the 

 longitudinal pull is increased. In calculating the coefficients from the 

 stress effect, we have taken care, to use such values of SI as are due to 

 very small loading, in order that the results may be comparable to 

 those obtained from the strains produced by magnetization. 



The diminution of —k' with increased loading is greater in the 

 weak than in strong fields. Applying equation (<l) for measuring the 

 length change produced by magnetization, we notice that —j- 

 diminishes with the coefficient /<;", so that we expect from the above 

 result the decrease in the contraction of nickel wire with increased 

 longitudinal pull ; but as the rate of diminution of k" becomes less as 

 the field strength, is increased, the diminution in the contraction will 

 not be so marked in the strong as in weak fields. This theoretical 

 conclusion is borne out by the experiments of Bid well on the effect of 

 longitudinal stress on the length change of nickel wire. The change 

 of volume i\uc to magnetization will somewhat diminish for nickel wire 

 under longitudinal pull, but the difference will not be so pronounced 



