Electromotive Force to Pressure fyc. 103 



The upper and lower ends of the tubes were wrapped in 

 cotton-wool. The following are the particulars of the ex- 

 periments :— 



Number of 

 experiment. 



Substance. 



Grains per oz. 



Number of 

 Tubes. 



Amount of 

 Deflexion. 



93. 

 94. 



KC1 



40 

 400 



2 



8 f 

 12 „ 



These results show that the amount of deflexion was in- 

 creased fifty per cent, by employing a solution of ten times 

 the degree of concentration (compare also experiments Nos. 3 

 and 5 with 6 and 8). The cotton-wool had no apparent effect 

 upon the amount of deflexion, thus showing that the unequal 

 temperature of the upper and lower parts of the room had no 

 perceptible effect. 



Period of Time required for Reversal. 



With zinc electrodes in the solution of KC10 3 (exp. 24) 

 and three tubes, the period required to attain the maximum 

 effect after a complete reversal was 4*5 minutes, and was the 

 same after standing vertical 15 hours. 



With zinc electrodes in the solution of Na 2 S0 4 (exp. 41) 

 and three tubes the time required to completely reverse was 

 10 minutes, and in the solution of KC1 (exp. 21) it was 

 15 minutes. 



With cadmium in the same solution of KC1 it was 13 

 minutes, and after standing vertical 18 hours it was again 

 13 minutes. 



The degree of fixity of the state produced varied, therefore, 

 both with different liquids and with different metals, but not 

 with lapse of time. 



Degree of Electromotive Force of the Current. 



This was measured by the method of balance with two 

 thermoelectric couples of iron and German-silver wires, the 

 junctions of which were immersed in melted paraffin at 

 120° C, the outer ends of the wires being at 20° C. With 

 zinc electrodes in two tubes and the solution of four grains of 

 KC1 per ounce of water, giving a deflexion of 8 degrees, as 

 in exp. 93, the electromotive force was equal to '00572 volt. 

 Wild (see note, ante) attempted to find the variation of 



