62 



Prof. Nagaoka and K. Honda on Magnetostriction 



of 1 mm. diam. by passing 6 amperes through it amounts 

 to about 28" per cm., while with nickel wire of 083 mm. 

 diam. under similar conditions, the maximum twist amounts 

 to about 200". 



Fig. u. 



5(0 j5 



Three different kinds of nickel-steel wires, for which our 

 thanks are due to Dr. Ch. Ed. Guillaume, were tested. The 

 results of the measurements are shown in fig. 12. 



The sense in which a nickel-steel wire twists is the same 

 as for iron. The amount of twist increases with the magnetic 

 field, but it soon reaches a maximum, to decrease afterwards 

 quite slowly as the field becomes stronger ; and the twist is 

 generally reversed in high fields. With the specimens tested, 

 the twist increases with the percentage of nickel. The 

 23*6 per cent. M and 39*2 per cent. ]S T i were examined in 

 a hard drawn state ; but the 45*2 per cent. Ni wire 

 was examined after annealing it in hydrogen, as already 

 described. 



Twist by varying the circular field. — In iron the twi^t 

 increases with the strength of the circular field if the longi- 

 tudinal field remains constant. Such is also the case with 

 nickel in moderate and strong fields. Jn low longitudinal 



