236 WIEDEMANN ON THE MOTION OF LIQUIDS 



for the latter could only be called into action by the gradual de- 

 composition of the liquids by the current. 



When, instead of water and the solution of sulphate of copper y 

 other liquids were introduced into the apparatus, the same 

 phaenomenon was observable. 



A solution of sulphate of zinc behaved exactly as a solution 

 of sulphate of copper. 



Solutions of sulphate of potash, sulphate of soda, &c., mani- 

 fested a weaker action than when, with equal intensity of cur- 

 rent, pure water was employed. With these, however, the 

 rapid liberation of gas during the decomposition of the solu- 

 tion always more or less impeded an exact observation. 



Dilute alcohol, as well as absolute alcohol, manifested the action 

 more powerfully than pure water. 



Dilute sulphuric add showed no action whatever (as Becquerel 

 before observed). 



If, in place of the porous clay above described, a plate of 

 gypsum, or a piece of bladder stretched over a glass frame, were 

 introduced, a transference of the liquids again occurred, in a 

 greater or less degree, the motion of the liquids having always 

 the same direction, i. e, from the positive to the negative elec- 

 trode. 



As yet the author has not succeeded in replacing the porous 

 diaphragms by single capillary tubes, or a system of such. The 

 least difference of hydrostatic pressure on each side of these 

 tubes is so much stronger than the action of the current, that 

 when the liquid in the capillary tubes was moved by the current 

 towards the negative electrode, the ascent of the liquid on the 

 negative side was sufficient immediately to annihilate the action 

 of the current, and cause the liquid to flow back. Even when 

 the level of the liquid^s surface on each side the capillary tubes 

 was kept constant, by means of a contrivance admitting of 

 an overflow on the one side and a supply on the other, no such 

 overflow could be produced. 



The reason of the failure of this and other experiments insti- 

 tuted for the purpose, probably was, that by employing one or 

 a few capillary tubes it is not possible to conduct even a pretty 

 strong galvanic current through the liquid contained in them ; 

 by employing many capillary tubes, or tubes with wider aper- 



