100 



Dr. G. Gore. 



produces an electric current, it is reasonable to infer that an electric 

 current passed through such a junction in the same direction as the 

 one produced, would tend to lower the temperature. And as it is 

 well known that both the cohesion of liquids and their elevation are 

 diminished by rise of temperature, it is probable that the electric 

 current, by producing a minute change of temperature at the junction, 

 affects to a slight extent the capillary elevation. By comparing, how- 

 ever, the directions of the electric currents obtained by heating 

 mercury in contact with various solutions which exercise no chemical 

 action upon it (see " Thermo-Electric Behaviour of Aqueous Solutions 

 with Mercurial Electrodes," " Proc. Roy. Soc," vol. 29, p. 472), with 

 the directions of movements produced by given directions of electric 

 currents in the same solutions in these experiments, it maybe perceived 

 that they do not to any large extent coincide. 



That the mercury should also conversely suffer slight changes of 

 temperature by electro -capillary action, is in accordance with the 

 discovery made by Pouillet (" Ann. de Chemie et de Phys.," vol. xx, 

 1822, pp. 141-162), that heat is evolved by the capillary absorption of 

 liquids by solids ; and with the experiments of Jungk (" Phil. Mag.," 

 vol. 2, 1876, p. 454; and "Pogg. Ann.," vol. cxxv, p. 292), and 

 further, with those of Melsens, who states that by mixing 4*45 grms. 

 of charcoal and 33 of bromine, the rise of temperature was 35° 

 ("Phil. Mag.," vol. 2, 1876, p. 454; also "Mem. de l'Acad. Royal de 

 Belgique," vol. xxiii). 



The movement is evidently not caused by heat of conduction 

 resistance, because that would produce expansion and advancing 

 motion only. If also the motion is simply due to thermic expansion, 

 then heat of chemical combination at the anode in cases of electrolysis 

 in the capillary ought to cause the mercury to move downwards, but 

 with solutions of potassic cyanide it moves the reverse. The relations 

 of electro-capillary movements to heat require, however, much more 

 investigation. 



8. Relations of the Movements to Electric Conditions. 



The phenomena of the capillary electroscope are not results of 

 electrolysis, nor of disruptive discharge, but of conduction proper, 

 and may occur either with or without electro-chemical change. In 

 nearly all previous investigations of the electric movements of mer- 

 cury, very much stronger electric currents were employed, and the 

 results were complicated by electrolytic phenomena. That electro- 

 lysis, when it does occur, is only a coincident circumstance, is proved 

 by the non- liberation of hydrogen at the meniscus when that surface 

 is made negative in dilute sulphuric acid and. in various other 

 solutions ; also, by the mercury at the meniscus not becoming viscid 

 when made the negative pole in a solution of cupric sulphate (see 



