CHANGE OF LENGTH BT MAGNETIZATION. g 



gradually disappears and at 312°C, the change of length is .similar to 

 thai of tungsten stee] at ordinary temperatures. With further in- 

 crease of temperature, the elongation, after passing a maximum, 

 gradually decreases. We could trace the elongation up to 970°C, 

 which is far higher than its critical temperature. The effeel of 

 cooling by liquid air is considerably large in strong fields, producing 

 an increase of contraction. 



The relation between the change of length and the temperature 

 is given in Fig. 5. It is remarkable to observe that the maximum 

 elongation in weak fields which is characteristic for iron, remains 

 almost constant for the temperatures ranging from -18G°C to 200°C. 

 Above this temperature, the elongation increases, till it reaches a 

 maximum, and then rapidly decreases. 



Tungsten steel. The results of experiments in tungsten steel 

 are given in Fiffs. 6 and 7. The course of the curves and its 

 change with temperature are similar to those of soft iron at tem- 

 peratures higher than 500°C. The change of length seems to disappear 

 nearly at the critical temperature, namely 900°C, a value obtained by 

 Professor H. Na^aoka and Mr. S. Kusakabe. The former result 

 obtained by one of us approximately agrees with the corresponding 

 result in the present experiment. 



With tungsten steel, we first studied the effect of temperature ; 

 when the specimen was cooled down to its initial temperature, it 

 underwent a considerable permanent change with regard to the 

 change of length. So the experiment in liquid air was performed 

 with another rod of square section cut from the same specimen as the 

 cylinder. The curves for 10°C and -186°C are given in Fig. S which 

 shows a slight effect of cooling on the change of length. Cooling 

 decreases the elongation of the alloy in weak fields, but increases it in 

 strong - fields. 



