102 



Dr. G. Gore. 



it with mercury whilst in a horizontal position ; then melted it off at 

 the point B by means of a minnte flame ; broke it off at C, and fixed 

 it vertically with its end C in dilnte sulphuric acid above an electrode. 

 Not a trace of air was visible in any part by the aid of a strong 

 magnifying glass. By charging the npper electrode by induction with 

 an electrophorus, the mercury descended freely; and by charging the 

 lower one it ascended, provided the free end was not insulated. The 

 motion of the mercury, therefore, is evidently not produced by mere 

 electric charge but requires electric flow. 



Even a residual electric charge of the ebonite base of the reverser 

 (see " Proc. Roy. Soc." vol. 30, p. 32) at the surfaces of contact of 

 that substance with the brass fittings which had been connected 

 with the poles of the nearly exhausted little water- cell was suf- 

 ficient to work the instrument. Also a voltaic current which raised 

 the meniscus 19*5 millims. would not produce a visible movement of 

 the needle of a torsion galvanometer having a coil of 100 ohms 

 resistance. These facts illustrate the extreme sensitiveness of the 

 instrument to electric flow of the feeblest tension ; and the apparatus 

 might be used for examining the conductivity proper of electrolytes. 



From the results achieved by Quincke ("Pogg. Ann.," vol. cxiii, 

 1861), and by Jurgensen (Reichert and Du Bois Reymond's " Ar- 

 chiv," 1860, p. 573; also "Chemical Physics," by W. A. Miller, 

 4th Edition, pp. 530-533), and the various results obtained by myself, 

 I conclude that the primary mechanical movement in the instrument 

 is due to a more or less charged electric state of the surfaces of the 

 liquids and tube. The electric tension accompanying that state alters 

 the degrees of adhesion of the substances to each other, and produces 

 electric convection, which, in consequence of the unequal adhesion of 

 the solution and mercury to the tube, produces a to-and-fro movement 

 of the mass. The less fundamental results, such as reversal of 

 direction of movement with solutions of potassic cyanide, or with 

 tubes of different diameter, would probably be found to be necessary 

 results of the above causes under the altered conditions. A brief 

 translation of Quincke's explanation of somewhat similar phenomena 

 may be found in W. A. Miller's " Chemical Physics," 4th Edition, 

 p. 532. 



The primary action appears to consist nearly wholly of a direct 

 conversion of electricity into mechanical power ; and this accords 

 with the great sensitiveness of the instrument and the comparatively 

 considerable force of the movements. This force has been already 

 applied by Lippmann in the construction of an electro- capillary engine. 

 The converse action, viz., the production of electric currents by 

 mechanically raising and lowering mercury and an acid solution in 

 capillary tubes, has also been obtained by Lippmann ("Phil. Mag.," 

 vol. 47, 1874, p. 281). 



