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machine ; and if E lay upon the semi- 

 circle 2R1, there was instability for the 

 second machine ; if E lay upon the semi- 

 circle 3 2 4, there was instability for the 

 first machine ; and if E lay upon the 

 semi-circle 4, 1, 3, there was stability for 

 the first machine. Thus the region 1, 5 

 3, had a double guarantee of stability. 

 The angle 1 D 3 was twice that of 

 electric lag ; which showed one of the 

 advantages of self-induction. Again, if a 

 line from A to 4 cut the E-circle in 6, 

 this would be the point for E giving 

 the maximum efficiency in the trans- 

 mission of power. It must lie in the 

 region of stability. The point 5 had 

 the property that the efficiency there 

 had the ratio of the two electromotive 

 forces, as in the case of steady cur- 

 rents, but it was not as great at 5 as 

 at 6. Fig. 34 had been constructed in the 

 same way as Fig. 33, and with the same 

 electromotive forces, but with a larger 

 angle of electric lag BAD. It was 

 intended to show by an example that 

 the point 3 did not necessarily lie within 



