236 



and clear mercury is placed upon a smooth non-metallic surface, a 

 watch-glass for example, and covered to a small depth with a watery 

 electrolyte, sulphuric acid in particular, and two terminal platinum 

 wires from a voltaic battery are dipped into the electrolyte, one on 

 each side of the globule, the mercury makes a movement towards 

 the negative wire, and a rapid and continuous stream of the super- 

 natant liquid flows from the negative to the positive electrode over 

 the surface of the mercury, and back again by the sides of the con- 

 taining vessel. Also that when a small drop of a watery electrolyte, 

 especially sulphuric acid, is placed upon the surface of pure and dry 

 mercury, the latter connected with the negative pole of a battery, 

 and a platinum wire from the other pole momentarily immersed in 

 the electrolyte, the drop of liquid is suddenly repelled and spreads 

 over the surface of the mercury. 



2. These phenomena have been examined by Herschel*, Erman, 

 H. Davy, Runge, Pfaff, and others f, and some of the results have 

 been recorded in the 1st volume of 'Gmelin's Handbook of Che- 

 mistry,' page 486 (published by the Cavendish Society) ; but no 

 definite cause of the movements seems to have been discovered. 

 Herschel has, however, shown that the continuous movement of the 

 supernatant liquid is unaffected by the approach of strong magnets, 

 and that it is influenced by the chemical nature of the electrolyte ; 

 also that its direction is notably influenced by the presence of vari- 

 ous metallic impurities in the mercury. 



3. Being desirous of ascertaining the conditions under which the 

 movements are produced, the relations of the phenomena to ordinary 

 and recognized actions, and the more immediate cause or causes of the 

 movements, Ihave undertaken the folio wing experimental investigation. 



4. In describing the experiments I shall have frequent occasion to 

 speak of the continuous flow of the electrolyte, and of the sudden re- 

 pulsion of drops of liquid already mentioned, and shall therefore 

 speak of the former as the continuous action or movement, and of the 

 latter as the sudden or momentary one. Also in speaking of the conti- 

 nuous motion, I shall call it positive flow or movement when the super- 



* " On certain Motions produced in Fluid Conductors when transmitting the 

 Electric Current," Phil. Trans. 1824. 



t Draper has recorded some experiments of a similar kind. Philosophical 

 Magazine, S. 3. vol. xxvi. p. 185. 



