340 H. R. Hamley and A. L. Rossiter : 



those obtained for transformer iron. The values of U obtained 

 by us are less than those obtained by Wilson, Winson and 

 O'Dell, and others, but are practically identical Avith the results 

 given by Barrett, Brown and Hadfield for a sample of silicon 

 iron closely allied to " Stalloy " in composition. 



Fig. 4, which shows the effect of variation of frequency 

 upon the retardation and permeability for the annealed sample, 

 is interesting in view of the results just referred to. In general 

 the results show a similarity of vai'iation to those obtained for 

 iron, that is increases regularly with increase of frequency 

 while yuo decreases. In both cases the maxima are reached at 

 about the same induction, those for at an induction of 4500 and 

 for /Xq at an induction of about 6500. 



One point is striking, namely, that the graphs for /x^ for fre- 

 quencies .035 and .02 intersect. Since there were a fair number 

 of points taken and the results were very different in the twa 

 cases, this cannot be due to experimental error nor to any varia- 

 tion in the wave form of the magnetizing current, for the tables 

 show this to be very constant. Corresponding to this deviation 

 from the usual result will be noticed a distinct difference in the 

 general appearance of the graphs for 6 which is not existent in 

 the graphs for iron. This correspondence is to be expected 

 seeing that [x^ and 6 each depend on Bj and o> as well as upon 

 the wave form of H,. Wliatever deviation from the usual rule for 

 iron there is, seems to have taken place in the middle frequency, 

 so that for this particular frequency /x,, is for inductions up 5000 

 less that one would expect. It may be possible that the previous 

 high current densities used in the lower frequency had some after 

 effect lasting until the maximum was reached, though precau- 

 tions were taken to avoid this. 



Summing up, therefore, generally, we may say that the chief 

 results to be noticed are that — ■ 



(1) "Stalloy" cannot be used to advantage in the un- 



annealed condition. 



(2) In the annealed state the results obtained fully bear 



out the claims made by the makers, the permea^ 

 bility being very high and the losses small, par- 

 ticularly the eddy-current loss. 



