189 



tial, so that the values of the dissipation 

 calculated from his experiments were 

 probably not too high for application to 

 such a case. With reference to " viscous 

 hysteresis" (p. 67), he had made no 

 direct observations showing that the 

 energy dissipated through hysteresis 

 increased with the speed at which the 

 cyclic change of induction was performed. 

 So far as any such observations had 

 been made, he understood that the 

 results had been negative, and that the 

 heating effect per cycle had been sensibly 

 the same whether the same cycle was 

 repeated with greater or with less 

 frequency. But there was a certain 

 amount of evidence that magnetization 

 took some time to be fully developed in 

 iron after the magnetizing force was 

 applied, especially when the magnetizing 

 force was low, and so far as this was true 

 it must have the effect of increasing the 

 dissipation of energy in cycles of high 

 frequency, since larger changes of mag- 

 netic force would then be required to 

 produce equal changes of magnetic 

 induction. 



