336 H. R Hdwlcy and A. L Rossifer : 



In making comparisons betAveen " Stalloy " and ordinary 

 iron the results obtained bv Professor Lvle for good samples 

 of transformer iron have been assumed. 



In Figs. 1, 2a, 21), the more important characteristics of 

 the induction waves which are set out in Tables I. and IV. are 

 plotted against the amplitudes of the first harmonics of these' 

 waves. 



The curves obtained for " Stalloy " are typical in general 

 appearance of those obtained for iron and, although plotted 

 here for only tlie lowest frequency, will be found similar in ap- 

 pearance for all the induction waves, provided the periods are 

 constant throughout a series of experiments and are produced 

 by currents of similar wave forms. 



The characteristics /x^ and 6 fall in all cases to low values as 

 the values of Bi become small and probably vanish with B^- 

 The rise of in the region of low densities is steeper for annealed 

 iron than for annealed "Stalloy," the appearance of the graph 

 for iron being somewhat like that drawn here for the unannealed 

 "Stalloy." There is this important difference, namely, that for 

 iron, frequently rises to maximum of 52° whereas for "Stalloy' 

 the maximum obtained for the same frequency was 47°. 



The effect of annealing upon d is to increase its magnitude for 

 all inductions over about 2000. It will be noticed in the accom 

 panying graph that the maximum value of increases on anneal- 

 ing from 33° to 38°. After attaining a maximum value for the 

 graph assumes a steady downward gradient, which is practically 

 constant for both annealed and unannealed samples. Along this 

 gradient there is approximately a constant difference in value 

 of of about 8° for all values of the above inductions. For 

 ordinary working inductions therefore 8° may be taken as the 

 increase effect produced upon $ by annealing. 



A difference in the appearance of the permeability curve is 

 to be noted. For iron this curve takes an almost parabolic form, 

 having its axis vertical and its apex at an induction of about 

 10,000 the maximum value of /x,, rising only a little above 

 3.000 generally. 



Annealed "Stalloy" has a maximum permea))ility of 4140 

 which is attained at an induction of 6500, while tlie unannealed 

 ring gives a maximum value of aljout 3100 at an induction of 



