OF ARTS AND SCIENCES. 



221 



circuit as at first. Tlie poles of the induction coil were connected, the 

 one directly, the other by means of the spark leaping between two 

 points with a condenser of ^ Farad capacity. The poles of the con- 

 denser were connected with a Thomson's galvanometer of 5880 ohms 

 resistance. Each of the following results is the mean of two observa- 

 tions. The length of spark was the same in both cases. 



The resistance of the six cells (Bunsen) was greater than the resist- 

 ance of the primary circuit. 



On another day, the same arrangement gave the following result, 

 where each is a mean of two observations : — 



In a great many cases, where the magnet was quite powerful, it 

 was not easy to get comparable results. Wl:\pn the primary circuit 

 was broken between the poles, the spot of light was driven off the 

 scale ; but, when the primary was broken outside, there was frequently 

 very little deflection. 



At another time, a Thomson's mirror galvanometer of 6 ohms re- 

 sistance gave, with an arrangement otherwise the same as above, the 

 following deflections as a mean of twelve observations : — 



Outside 12.9 



Inside 15.37. 



When the electro-magnet was in a separate circuit from the primary 

 of the induction coil, the following observations were obtained with the 

 Thomson's galvanometer. Each result is the mean of about twenty 

 observations. 



