314 Mr. A. Tribe on Electrolysis. [Feb. 17, 



strips, after the lapse of thirty minutes, not a trace of copper could be 

 seen on the glass, a little on the negative end of the charcoal (facing 

 the positive electrode), and more on the platinum. 



Experiment IX. — In the centre of a glass trough, containing a 5-per- 

 cent, solution of potassium chloride, was fixed a post midway between 

 platinum electrodes 5 inches apart. Pieces of different metals \\ inch 

 long and \ inch wide were successively inserted in a slit in the upper 

 part of the post, lengthwise in a line with the poles, and the amount of 

 gas given off from the negative extremity during five minutes was 

 determined. 



Zinc gave 19*5 measures. 



Aluminium 15-2 



Copper 1-7 



Lead 1-6 



Silver 1:3 



Platinum 1*0 



In the language of G-rotthus's hypothesis, the foregoing experiments 

 may be explained thus : — The greater amount of copper found on the 

 longer silver strip in Experiment VII. may be accounted for (1) by its 

 being subjected to the influence of a greater number of polarized mole- 

 cules, (2) by its tendency to electric equilibration being less, and (3) by the 

 smaller number of molecules between its ends and the battery-electrodes 

 inducing a more rapid discharge. 



The absence of copper on the glass, the presence of a little on the 

 carbon, and more on the platinum in Experiment VIII. is explained by 

 the difference in the capability of these bodies to be polarized en masse. 



The results of Experiment IX. are due in great part to the specific 

 affinities of the metals for the chlorine of the potassium chloride ; in 

 great part, because the different metals are polarized en masse with more 

 or less facility, and the result is affected accordingly ; but were the con- 

 ductivity of the metals equal, we might expect the rapidity of the dis- 

 charge to be proportional to the specific affinities. 



It now appeared desirable to obtain some experimental knowledge of 

 the general direction of the lines of the discharge between electrodes of 

 small dimensions. 



Eor this purpose 198 silver strips were placed in as many posts fixed 

 into a wooden stand. The arrangement of these, as well as the position 

 in which the electrodes w 'ere placed, is shown in the accompanying diagram. 

 Connexion was made with the battery for an hour, after which the copper 

 sulphate was removed from the trough, and each strip examined. Those 

 on which copper was visible, as well as its position on the strip, are 

 thus marked in the figure, (— i— ; t signifies the merest trace, and ? 

 doubtful. 



The position of the copper on the strips, indicative as it is of their 



