161 



tation that which was counter-clock- 

 wise, set off the angle B A D in the 

 negative direction, equal to that of 



electric lag (Tan B A D = =^, where 



L = the coefficient of self-induction, R 

 =r. the resistance of the circuit, and T == 

 the semi-period). From B and C drop 

 perpendiculars upon A D, cutting it in 

 D and 5 (not given in Fig. 33 to avoid 

 confusion of lines). D would obviously 

 be on the circle already drawn. With D 

 as center, and D 5 as radius, describe a 

 circle, called the E-circle, cutting the 

 former circle in Q and R. Then all 

 possible phase-differences between the 

 two machines might be represented by 

 some angle A D E, where E was always 

 upon the E-circle. For any point E the 

 electromotive forces of the two machines 

 were related in phase and magnitude, 

 exactly as were A D, D E. For example, 

 if E was at the point 5, the phase-angle 

 was ]80°; or the electromotive force of 

 one machine was throughout its varia- 

 tions always opposed by the electromo- 



