241 



reform, and above this, in one instance a dilute solution of sulphate 

 of alumina ; and in the other instance, asolution of caustic potash, 

 and the wires from the battery dipped into the upper liquid ; no 

 movements at either of the contiguous surfaces occurred, 2nd. 

 Similar experiments were made, substituting in one case a definite 

 layer of oil of vitriol with a very dilute solution of sulphuric acid 

 above it, and in the other case a dense solution of chloride of zinc 

 with a very dilute solution of the same salt above it, for the chloro- 

 form and its supernatant liquid ; in each case only feeble movements 

 in the usual direction at the surface of the mercury occurred ; the 

 weakness of the movements was probably a consequence of the in- 

 creased distance of the electrodes from the mercury. 3rd. The lower 

 part of a V-tube of half an inch bore was just filled with mercury, 

 and a small quantity of solution of cyanide of potassium poured into 

 each leg ; on dipping the polar wires, one into the solution of each 

 leg, the saline liquid rapidly flowed from the positive to the negative 

 leg until it was 1^ inch high in that limb. From these experiments 

 I infer that the electric current must pass from the electrolyte into 

 the metal, or vice versa, and that the continuous movements are not 

 results of any power radiating from the electrodes. 



1 7. It is not essential that the electric current should pass both 

 into and out of the metallic globule by the electrolyte ; with a glo- 

 bule of mercury in rather strong sulphuric acid and either of the 

 polar wires immersed in the acid, the other wire being in contact 

 with mercury, the movements occurred : also with the negative 

 wire touching a globule of mercury in a solution either of cyanide of 

 potassium or strong caustic potash and the positive wire in the 

 liquid, movements were readily obtained. 



18. To ascertain whether the electrodes were essential to the 

 movements, I placed a large globule of mercury in the middle 

 part of a slightly bent horizontal glass tube, 20 inches long and 

 \ an inch diameter, then filled the tube with a strong solution of 

 cyanide of potassium, and immersed the polar wires a short di- 

 stance in the liquid at each end; a strong positive flow of the 

 solution over the surface of the mercury occurred, but no movements 

 took place at the surfaces of the electrodes, except such as were 

 produced by the evolution of gas. The electrodes evidently operate 

 merely as conductors of the electricity, and are not, in an abstract 

 sense, at all connected with the movements. 



