50 Prof, Nagaoka and K. Honda on Magnetostriction 



at present obtainable. The rod was turned into an ovoid, 

 and its change of length measured in the manner already 

 described in our former paper. 



In low fields the ovoid elongates and reaches a maximum, 

 whence it gradually diminishes, till it indicates no elongation. 

 The decrease goes on steadily, but the rate of change becomes 

 gradually less, and ultimately assumes an asymptotic value. 

 As will be seen from the curve of the length-change (see 

 fig. 2), the general feature resembles that of iron, with slight 

 difference in quantitative details. 



(b) Nickel (fig. 2). 



The nickel ovoid which we formerly used for the measure- 

 ment of length and volume changes was prepared from 

 a thick plate of the same metal. Although the ovoid was 

 heated in a charcoal fire for several days lack of homo- 

 geneity was undeniable. To guard against such mischances 

 we have tested a new specimen supplied by Johnson and 

 Matthey, shaped into an ovoid from a cylindrical rod. 



The nature of the change does not materially vary from 

 the former specimen. In weak fields the contraction takes 

 place at first slowly, but gradually at an increased rate. 

 Between fields 5 and 100 the rate of diminution is very rapid, 



Tier. 2. 



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-20 



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but the change becomes at last asymptotic, when it amounts 

 to about 38 x 10~ 6 . It appears from the curve (see fig. 2) 



