284 



BELL SYSTEM TECHNICAL JOURNAL 



dimension is about 10"^ cm or less. Many studies have been made of thin 

 electrodeposited and evaporated films. Generally it is found that the per- 

 meability is low and the coercive force high. The interpretation is uncertain 



5 5 



COERCIVE FORCE, He, IN OERSTEDS 



tO^x 15 



10 5 5 10 



RESIDUAL INDUCTION, Bp, IN GAUSSES 



15 X 10^ 



50 50 



INITIAL PERMEABILITY,//,) 



100 



10^x3 



1 1 



MAXIMUM PERMEABILITY, fJL^ 



3X103 



Fig. 35 — Properties of the same material as that of Fig. 34, after it has been rolled, 

 annealed, and again rolled. 



I 2 3 4 5 6 



PER CENT SILICON IN IRON 



Mg. 36 -Variation of the breaking strength of iron-silicon alloys, showing the onset of 

 brittlcness near 4 per cent silicon. 



because it is difficult to separate the effects of strains and air gaps from the 

 intrinsic effect of thickness, though it is known that each one of these vari- 

 ables has a definite effect. As one example of the many experiments, we 



