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Dr. John Hopkinson said that one of 

 the questions with which the author 

 dealt was how many alternations per 

 second was it most appropriate to use for 

 distribution by transformers? It was 

 clear that the answer depended upon a 

 balance of advantages. No one would 

 use exceedingly few alternations ; no one 

 would advocate a greater number than 

 some superior limit much less than the 

 greatest it was possible to produce. In 

 favor of a high frequency was the fact 

 that, for a given efficiency, the trans- 

 former would be cheaper to manufacture. 

 On the other hand, in favor of a low 

 frequency, the whole of the conductor 

 was not equally used with alternating 

 currents. The author had alluded to the 

 question of a viscous hysteresis in mag- 

 netization of iron. Dr. Hopkinson 

 doubted the propriety of the term vis- 

 cous hysteresis, but he knew what was 

 meant. There was, he believed, no satis- 

 factory evidence of the existence of so- 

 called viscous hysteresis, and it was 

 certainly a phenomenon by no means so 



