induced electromotive force. Having 

 obtained this curve, which the author 

 suggests should be called the static 

 characteristic, the dynamic characteristic 

 of the machine is determined for a cer- 

 tain current through the armature, by so 

 adjusting the resistance in the external 

 circuit, that for all exciting powers the 

 current remains the same. It is import- 

 ant that the external circuit should not 

 contain any appreciable amount of self- 

 induction — a condition easily fulfilled if, 

 during the experiment, the machine be 

 set to work a bank of transformers which 

 are feeding glow-lamps. The curve so 

 obtained must obviously lie wholly under 

 the first curve, and the difference be- 

 tween the ordinates of the two curves 

 depends upon the choice of current for 

 which the second test has been made, 

 and upon armature resistance and self- 

 induction. Besides these two curves 

 there is a third, namely, that obtained 

 when the machine is driven as a motor 

 running light. To find this curve it 

 would be necessary to have at disposal 



