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3. Gave the same class of results as re- 

 garded primary electromotive force and 

 current ; but here also the curve of 

 secondary electromotive force was very 

 different. Owing to the fall in positive 

 value of electromotive force being dis- 

 continuous with the rise in negative 

 electromotive force, there were two im- 

 pulses of secondary electromotive force, 

 corresponding to each impulse of primary 

 electromotive force. The effect of this 

 was to double the loss from magnetic 

 friction, or hysteresis, in any magnetic 

 apparatus in the secondary circuit. That 

 at once showed the very important bear- 

 ing of the question of the law of elec- 

 tromotive force, and the errors that 

 might be introduced by assuming a 

 simple sine function. He had alluded to 

 the difficulty of treating the matter ana- 

 lytically and graphically ; but there was 

 one mode of treating it which he had not 

 seen mentioned, the idea of which oc- 

 curred to him two years ago, and he had 

 designed some machines for carrying it 

 out, namely, treating the subject by means 



