220 



PROCEEDINGS OF THE AMERICAN ACADEMY 



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 pole 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 i)roper 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 magnet, the electro-mag- 

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



