220 



PROCEEDINGS OP THE AMERICAN ACADEIklY 



was employed. The electro-magnet was placed in a circuit with two 

 Grove cells. To the end of one of the large wires used for breaking 

 the circuit a very fine wire was fastened, leading to one pole of 

 a Thomson's Quadrant Electrometer, whose other jiole was put to 

 earth. Whenever the two large wires were separated, there was of 

 course a deflection of the electrometer mirror corresponding to the 

 difference of potential of the poles of the battery ; but, beside this, 

 there was an increased effect when the circuit was broken between 

 the poles, that seems to be unaccountable, if we assume the effect to be 

 mechanical. 



When a condenser of about 1 Farad capacity was put into the cir- 

 cuit, the following deflections were obtained : — 



When no condenser was used, the deflections were as follows : — 



The electro-motive force in the circuit was very small, hardly enough 

 to render the poles strongly magnetic. With a proper electro-motive 

 force, we might expect the effects to be more striking. 



In order to measure the increase of quantity obtained by breaking 

 the primary circuit between the poles of the m;\gnet, the electro-mag- 

 net and the primary of an induction coil were placed in the same 



