ART. U.—K. HONDA .\ND S. SHIMIZU : OHAX(jE TX LEX(iTH 



4. Soft Iron. Fig. 1 represents the carves of the change of 

 length in soft iron plotted jigainst the magnetizing field ; T is the 

 tension per square millimeter. The curve T = is the result obtained 

 by means of Professor Nagaoka's apparatus ; our arrangement can not 

 be used for the measurement of the change of length corresponding 

 to no tension. The comparison of this curve with the others shows 

 the trustworthiness of the present arrangement for measuring the 

 minute change in length. 



The specimen was very well annealed, and so the initial 

 elongation was greatly reduced. The eflect of tension is to reduce the 

 elono-ation in weak fields and to increase the contraction in strong 

 fields. This diminution of elongation becomes greater as the tension 

 increases, till the initial elongation vanishes in a tension of about 4 

 kilograms per square millimeter. When the tension exceeds this 

 value, the course of the curve is changed. Li higher fields greater 

 than 40 C.G.S. units, all the curves are nearly parallel to each other. 

 It is also observed that the efiect of tension is comparatively larger 

 when the load is small than when it is heavy. 



