316 M. P, Riess on the Passage of Electric Currents 



Heat in the discharging circuit when interrupted by air of 

 1 line of mercury pressure. 



The following is the result of all tlie above observations, 

 showing the relation between the heat developed and the direc- 

 tion of the discharge current : — 



Current from the surface to the knob : heat 100. 

 Current from the knob to the svirface : heat 108. 

 In another scries of experiments, the knob in the glass cylin- 

 der was 2"7 inches distant from the platinum surface in the glass 

 plate. 



Here is the mean result : — 



Current from the surface to the knob : heat 100. 

 Current from the knob to the surface : heat 140. 



In order to employ stronger charges of the battery (up to a 

 quantity of electricity equal to 16), I replaced the thin platinum 

 wire in the thermometer by a thicker, and found the following 

 to be the mean result of four observations : — 



Current from the surface to the knob : heat 100. 



Current from the knob to the surface : heat 130. 



The knob in the glass cylinder was replaced by a horizontal 

 brass disc, -j-^ths of an inch in diameter, and 1 line distant from 

 the platinum surface in the glass plate. The results were : — 



Current from the surface to the disc : heat 100. 

 Current from the disc to the surface : heat 122. 



I removed the disc so that the brass rod alone remained in 

 the glass cylinder; it was 2 j^ inches long, and its point was 

 l^ths of an inch distant from the platinum surface. Tlie follow- 

 in"; were the results : — 



