Phenomena of the Capillary Electroscope. 



97 



a mixture of 30 grms. of charcoal and 23 cub. centims. of the 

 sulphide contained in a glass tube immersed in boiling water (see 

 " Phil. Mag.," July, 1877, p. 43). 



It is evident also that the movements must be greatly affected by 

 the relative degrees with which each of the liquids adhere to the 

 containing tube, and it is not improbable that as the aqueous solutions 

 adhere to the glass tube and the mercury does not, the latter yields to 

 the moving influence to a very much greater extent than the former, 

 and that the motion is chiefly (if not wholly) produced through the 

 agency of the adhesion of the solution to the tube, and not so much 

 through that of the mercury. 



Although the motion is frequently prevented by adhesion of the 

 mercury to the tube, it is not caused simply by diminution of that 

 adhesion whilst under the influence of the current, because if that did 

 occur, it could only operate by allowing some dynamic cause to produce 

 the motion. 



The evidence with regard to adhesion supports the hypothesis that 

 the motion is primarily due to a direct mechanical action at the 

 immediate surfaces of contact of the mercury and solution, producing 

 movements of solution and mercury in directions agreeing with those 

 in the annexed figures ; # and the to-and-fro movement of the mass is 



Fig. 2. 

 In KCy solution. 



Dvrccticrv of E lectric ctwrcrtt >~ 



In dilute sulphuric acid. 



a secondary circumstance, arising from the former in consequence of 

 the greater adhesion of the solution than of the mercury to the tube. 



* The repulsive action being usually at the negative pole in liquids, is a similar 

 fact to the molecular repulsion of highly rarefied gases at the negative electrode in 

 Mr. Crookes's experiments. 



VOL. XXXII. H 



