106 



BELL SYSTEM TECHNICAL JOURNAL 



different scales, the values of initial permeability in similar ring 

 samples of permalloy and of annealed armco iron, and small portions 

 of the corresponding ^u-H curves from which these were obtained. 



We have measured the magnetization of permalloy at saturation 

 and find that it is not sensitive to heat-treatment. The saturation 

 values of magnetization per gramatom are known to vary almost 



00 000 



40 000 



30000 t 



20000 



10000 



-FIG. 2 



PERMEABILITr CORVES 

 FOR LOW MAGNETIZING 

 FORCES 



5CO00 



40000 



30000 



20000 



10000 



400 



300 



ZOO 



100 



.01 



4RMC0 IRON 



MAGNETIZING FORCE M 



02 



400 



300 



ZOO 



100 



.03 



-04 



Fig. 2 



.00 



.06 



.01 



linearly with composition throughout the nickel-iron series, from 222 

 for iron to 59 for nickel. 4 The value 84 which we have found for the 

 78.5 per cent nickel alloy is therefore not abnormal. 



The magnetic characteristics of heat-treated ring samples of the 

 same alloy have also been determined through a wider range of field 



4 P. Weiss, Faraday Society Trans. 8, 149-156 (1912). 



