88 K. HONDA. 



Here we observe that circular magnetization produces con- 

 traction which increases very slowly at first, but afterwards 

 quite rapidly, till it reaches a nearly constant value. The 

 existence of the field of maxioium contraction is still a question. 

 The result is somewhat discordant as compared with that of Bid- 

 well with an iron ring, in which case the diminution vanishes 

 in a field of about 86 C. G. S. units. Since the behaviour of wol- 

 fram steel as regards the change of dimensions by magnetization is 

 very different from that of soft iron, the cause of the discrepancy 

 is probably to be sought for in the difference of the specimens. 



That the effect of longitudinal field on the change of length 

 by circular magnetization is of the same nature as in the case 

 of nickel, except that the sign of the change is opposite, is also 

 apparent from the same figure. As we have remarked, Beatson 

 and Riglii observed the same phenomenon. 



11. The middle curve in Fig. 6 represents the change of 

 length by longitudinal magnetization at the temperature of the 

 room. The lower curve was obtained at 80.2° C, and the upper 

 curve at the same temperature by reversing the key so as to 

 produce circular field. From the figure, we see that the be- 

 haviour of wolfram steel as re2;ards the clian2;e of leuirth is 

 widely different from that of other sorts of iron. It is remark- 

 al)le that the length of the tube, after reaching the maximum 

 elongation, diminishes very slowly as the field is increased, a 

 fact already noticed by the experiment^' referred to. In that 

 case, the maximum elongation was somewhat less than in the 

 present experiment. The discordance between the two is pro- 

 bably due to the difference of annealing and also ^of the shape 

 of the specimens. 



1) Nagiioka and lloiiila, loc. cit. 



