6S H. NAGAOKA AND K. HONDA. 



14. The curves for // and //' present the same general feature 

 in iron and steel. ,'/ increases inl[io\v fields; and tliere attaining 

 tlie maximum v^alue, it rapidly diminishes till it becomes less than 

 zero ; it then reaches a minimum, after Avhich it again gradually 

 increases. The exact position of the minimum is very vague ; the 

 curve for // ultimately coincides with the axis of IT. ]/' is at first 

 negative, and attaining the minimum value, goes on gradually 

 increasing till it becomes greater than zero, and then reaches a 

 maximum. AVith the farther increase of the field, the value of //' 

 decreases very slowly. The position of maximum for k' and that of 

 minimum for //' lie nearly in the same field, which is greater for 

 wolfram steel than for soft iron, while that for ordinary steel oc- 

 cupies an intermediate position. The absolute value of // and //' 

 is greater in iron than in steel. In nickel, the values of // and //' 

 are far greater than those for iron and steel, and moreover are of 

 opposite signs. The maximum of /,", or the minimum of /.', seems 

 to lie in a weak field ; the rate of decrease or increase is quite 

 rapid and the curves for // and Z " soon approach the axis of//. 

 Compared with the results of former experiments, the absolute 

 values of /,' and /." are generally small for iron, — far greater for 

 nickel. This difterence arises from the fact that for iron, the 

 change of length in weak fields is less in this case than in the 

 former experiment, and that for nickel the contrary is the case. 

 As regards the sign, these two experiments show fair agreement. 



Consequences of the theory. 



15. Effect of longitudinal pull. — The change of magnetization 

 produced by the elongation of a wire can be easily calculated 

 from the formula 



