TVw ft 
592 Proceedings of Royal Society of Edinburgh. [sbss. 
Again, in nickel X is negative in all fields, whereas in iron it is 
positive in low and moderate fields. Consequently in iron, when 
the circular magnetization is right-handed with reference to the 
longitudinal magnetization, the twist is right-handed also in low 
and moderate fields and left-handed in high fields. In the case of 
nickel the twist is left-handed throughout. 
Let us now make a quantitative comparison between r and the 
observed twist. For this purpose it will suffice to take the most 
complete series from Table II., namely, the second, third, sixth, 
and seventh, and tabulate the calculated and observed twists 
alongside of one another. The columns headed t contain the 
calculated twists, and the calculations are made for longitudinal 
fields 20, 40, 60, 80, 100, and 150. The corresponding values of 
-(X-[x), taken by interpolation from Table I., are 4, 11, 17-8, 
24, 29, 36*3, multiplied by 10“ 6 . The twists in Table IY. are 
expressed in millionths of a radian (10 ~ 6 ). 
