152 Royal Society : — 



mersed in the supernatant liquid ; a steady negative flow occurred in 

 each case. 2nd. Cadmium was similarly treated under fused cyanide 

 of potassium, and a positive flow obtained. 3rd. Cadmium, lead, 

 Britannia-metal, and fusible metal were melted separately, small pieces 

 of cyanide of potassium placed upon them and melted, the metal con- 

 nected with the negative platiuum wire, and the positive wire dipped 

 into the melted cyanide; positive repulsions took place with each 

 metal on making contact. I conclude from these experiments that 

 the power of rotating under the influence of an electrolytic current is 

 a general property of metals and alloys when in a liquid state. 



1 1 . That the mass or body of the metal is not essential to the 

 production of the movements, is evident from the fact that the move- 

 ments have been readily obtained with thin layers of mercury upon 

 amalgamated zinc (7) and copper plates. 



12. I have endeavoured to obtain the movements without the 

 presence of an electrolyte, by passing an electric current through a 

 small globule of zinc fused upon the surface of bismuth, but the 

 ready mingling of the melted metals, and their rapid oxidation, pre- 

 vented a reliable experiment being made. 



13. It has already been shown, in the instances of fused salts upon 

 melted metals (10), that the presence of water is not a necessary 

 condition of the phenomena. 



14. The power of producing the movements is a general property 

 of electrolytes as well as of liquid metals ; I have experimentally 

 found it in the following classes of substances : — organic and in- 

 organic acids ; water ; aqueous solutions of caustic alkalies* ; alkaline 

 carbonates, bicarbonates, borates, hypophosphites, phosphates, sul- 

 phides, hyposulphites, sulphites, sulphates, bisulphates, iodides, bro- 

 mides, chlorides, chlorates, nitrates, and silicates ; salts of alkaline 

 earths and of alumina ; salts of tungsten, molybdenum, chromium, 

 uranium, manganese, arsenic, and of the malleable heavy metals ; also 

 with fused salts, aqueous solutions of organic salts, and solutions of 

 salts in alcohol. The salts of tungsten, molybdenum, chromium, 

 uranium, and manganese, generally gave the weakest and most 

 variable results ; whilst sulphuric acid and solutions of alkaline 

 cyanides yielded very strong and definite movements. In feeble 

 cases of motion the globule of mercury should be placed in a narrow 

 porcelain boat, and a strong solution of the substance added until 

 the metal is only covered at its sides with the liquid ; and for still 

 greater sensitiveness, the experiment of placing a drop of the liquid 

 upon the surface of the mercury should be adopted. 



15. The mass or body of the liquid is not essential to the move- 

 ments ; mere films of solution adhering to the under surface of a 

 circular disc of brass, brought into contact with mercury under the 

 influence of a voltaic current, exhibited the phenomenon readily. 



* Herschel found no movements with solutions of caustic alkalies ( Vide Gmelin's 

 Handbook, vol. i. page 490) ; I have readily obtained them with pure mercury in 

 solutions of pure alkalies by using strong solutions and a powerful electric current, 

 and placing only a small quantity of the liquid above the mercury so as to pro- 

 duce the maximum of effect. Alkaline solutions in general act much more feebly 

 than acids. 



