CHANGE OF ELASTIC CONSTANTS OF FERROMAGNETICS. 



47 



^=5.0° 



In nickel, the change of rigidity and the effect of tension 

 are very remarkable. Under small tension, the rigidity first in- 

 creases slightly, then decreases rapidly as the field is increased, 

 attains a minimum and gradually increases, till in a certain field, 

 it recovers its initial value. As the field is further increased, the 

 rigidity increases by magnetization. If the tension is increased, 

 the field corresponding to the maximum decrease moves towards 

 higher fields, and the amount of decrease is remarkably increased. 

 Tensions here used were so adjusted as to be nearly equal to 

 those in the oscillation method. The effect of the amplitude of 

 twist was to diminish the change of rigidity in its absolute 

 amount. 



Comparing the above results with those of the oscillation 

 method, we notice that in weak tensions, the curve of the change 

 of rigidity as given by Barus's method lies considerably above 

 the curve of the change by the oscillation method, and that in 

 greater tensions, the contrary is the case. 



