Electricity in Electrolytes. 105 



11. The question has lately been several times discussed, 

 whether, in conductors of the second class, besides the conduc- 

 tion by means of electrolysis, another kind similar to that in 

 conductors of the first class also takes place. 



From a theoretical point of view, the hypothesis of the co- 

 existence of both kinds of conduction in one and the same body 

 appears to me admissible. The determination, however, in par- 

 ticular cases of the quantitative relation between the two kinds 

 of conduction, must, for the present at least, continue to be 

 referred to experimental research, in consequence of the absence 

 of accurately established facts whereon to base theoretical con- 

 clusions. 



With respect to the bodies hitherto examined in this respect, 

 and which, on account of their frequent application, are most 

 important, it has been found that conduction without electrolysis, 

 if it at all exists, is at any rate very small ; hence it will not 

 here be necessary to consider this kind of conduction, which, 

 indeed, would offer little essentially new in a theoretical point 

 of view. 



12. Lastly, there remains a phsenomenon to be mentioned 

 which, in many cases, accompanies electric conduction : I refer 

 to that of the translation of the liquid in the direction of the 

 positive current which accompanies the passage of the latter 

 through a porous partition. 



Wiedemann* especially has carefully examined this phajuo- 

 menon, and by so doing, has arrived at a series of laws of import- 

 ance in the theory of the phsenomenon. Towards the end 

 of his first memoir, many of these laws are comprised in the fol- 

 lowing theorem : — " An electric tension which exists on both 

 sides of a porous partition immersed in any liquid, transports 

 the latter from the positive to the negative side with a force 

 equal to a hydrostatic pressure directly proportional to that 

 tension." 



What Wiedemann here calls the electric tension, is, in mathe- 

 matical language, the difference between the values of the po- 

 tential function of the free electricity at the two limiting surfaces 

 of the porous partition ; hence if we bear in mind in what man- 

 ner the electric force acting within the porous partition, and 

 occasioning the current, depends upon that difference, we shall 

 find that the above theorem may be more simply expressed tlius: — 

 The force which drives the liquid through the porous partition is 

 proportional to the force which drives the electricity through the 

 same. 



This principle is so simple, that one might, perhaps, be thereby 



* P. 



Popgendorff's Annalen, vol. lx.\xvii, p. o21, and vol. xcix. p. 177. 

 Also Phil. Mag. vol. iv. p. 54G. 



