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induction-curve of individual coils was not 

 symmetrical, but as, in the machine, the 

 coils were joined in pairs, it came out that, 

 though considering any coil by itself there 

 was a want of symmetry, when the coils 

 were joined up all in series, the induction- 

 curve of the whole machine was quite 

 symmetrical ; it was almost exactly a 

 curve of sines. Mr. Mordey had meas- 

 ured the induction through a pair of coils 

 for all different positions of the field- 

 magnet in a whole period, and, as the 

 curves showed that the induction lay 

 within the curves of sines at some parts, 

 so the curve for the electromotive force 

 lay at some parts outside the curve of 

 sines. He should like to have some 

 definite information regarding the amount 

 of power required to reverse the mag- 

 netism in the ring-cores of alternating 

 dynamos for different degrees of mag- 

 netization. He had been making some 

 investigations into the subject, and had 

 found that to prevent the cores of alter- 

 nate-current dynamos from over- heating, 

 the thickness of the iron core for 100 



