274 Messrs. H. Nagaoka and K. Honda on Magnetostriction. 



H = 54 is less than -^^ of the intensity of magnetization. 

 During a pressure cycle there is distinct hysteresis, and the 

 curve of the change of magnetization generally forms a single 

 loop. On account of the inconstancy of the field, the mea- 

 surement with the ovoid could not extend beyond H=15 ; 

 with the iron cylinder H = 54 was the strongest field in 

 which the cyclic change could safely be observed. 



If, from experiments of pressure cycles, the curves of the 

 change in magnetization for constant pressure in different 

 fields be plotted, we obtain fig. 10, when the change of mag- 

 netization due to contraction of volume is not taken into 

 account ; if the correction be applied, then we obtain fig. 11. 

 These curves show that the range of the change in magneti- 

 zation due to pressure increases with the field ; the increase 

 takes place very rapidly at first, but becomes asymptotic in 

 moderate fields. Plotting these changes against magnetiza- 

 tion we obtain figs. 12 and 13. 



Comparing these curves with those for the change of 

 volume by magnetization, we find similarity between the two. 

 It is interesting to remark that whereas increase of magnetiza- 

 tion produces increase of volume in iron, the diminution of 

 volume produces diminution of magnetization. Thus a reci- 

 procal relation between the strain caused by magnetization 

 and the effect of compressional stress on the magnetization 

 of iron is established. 



Results in Nickel. — The curves of pressure cycle in nickel 

 are shown in figs. 14 and 15 (PI. II.). The change of mag- 

 netization wrought by compression is exceedingly small, but 

 comparatively greater than those in iron, and the hysteresis 

 during the cycle is more decided. Whereas hydrostatic pres- 

 sure causes diminution of magnetization in iron, there is 

 increase of magnetization in nickel. Similar to other effects 

 of stress as stretching and twisting, we find that the change 

 in iron is opposite to that in nickel. 



The curves of the change of magnetization by constant 

 pressure in different fields (figs. 14 and 15) show that there 

 is increase of magnetization in weak fields until it reaches a 

 maximum in moderate fields ; it then goes on slowly decreas- 

 ing. This feature is characteristic of all pressures up to 250. 

 atmospheres. Plotted against magnetization, the general 

 appearance of the curves is the same as that for magnetizing 

 fields (figs. 11) and 17, PI. II.) 



Comparing these curves with those obtained from chano-e 

 of volume by magnetization, we notice that whereas increase 

 of magnetization produces diminution of volume in nickel, the 

 diminution of volume produces increase of magnetization. 



