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mary current. Measurements had also 

 been made by a number of students to 

 ascertain the lag between the primary 

 and the secondary current. The second- 

 ary circuit was sending a current through 

 a non-inductive resistance. For all 

 speeds varying from about 1,600 semi- 

 alternations, up to 16,000 semi-alterna- 

 tions per minute, there appeared to be a 

 lag of about 90° above the lag which 

 ought to be got, which would really cor- 

 respond to the maximum lag possible. 

 In fact, there seemed to be a considerable 

 amount of self-induction in a transformer, 

 even when the secondary circuit was 

 employed to send a current through 

 glow-lamps, or a non-inductive circuit. 

 Without lag, the wave of the secondary 

 current must necessarily be 90° behind 

 the wave of the primary ; but instead of 

 that, the former was 180° behind the lat- 

 ter, so that there were 90° extra lag in a 

 transformer. The same result had been 

 observed by Mr. Blakesley later on, and 

 referred to in a paper read before the 



