in Mercury by Deoxidation. 499 



If at any moment the electric circuit was interrupted, the 

 weight required to detach the disk immediately increased, 

 showing that the relaxation of surface-tension was due to the 

 process of oxidation, and not to the presence of oxide only. 



It is evident from the foregoing experiments: — (1) that the 

 deoxidation of an ordinary surface of mercury to a slight ex- 

 tent increases its surface-tension ; but when the deoxida- 

 tion is as complete as it can become in the liquid employed, 

 no further change appears to take place by increasing the 

 battery-power ; and (2) that Avith the mercury in process of 

 oxidation we have to deal with a surface which is being trans- 

 formed into a substance with little or no cohesion, at a rate 

 increasing with a stronger current. 



In this investigation I have confined myself to some of the 

 direct effects of deoxidation of mercurial surfaces. There are 

 other well-known phenomena of the motions of mercury in 

 which the reduction of other metals from solutions plays an 

 important part ; but they are beyond the purpose of the pre- 

 sent inquiry. 



To sum up the results, we are, I think, entitled to con- 

 clude : — 



(1) That the electricity disengaged between pure mercury 

 surfaces (when not hydrogenized) is due to different states of 

 oxidation. 



(2) That the motions observed to take place in mercury 

 electrodes under water (or dilute sulphuric acid) are due to the 

 displacement of the surface corresponding to the different 

 atomic volumes of the metal and its suboxide (or suboxide and 

 sulphate). 



(3) That the pumping action of a column of mercury in a 

 tube or narrow channel is due to rapid circulation caused by 

 such displacement. 



(4) That these motions are not due to change of either con- 

 stant of capillarity or adhesion. And, finally, 



(5) That we may give a negative answer to Draper's 

 question, viz. "Is capillary attraction an electrical pheno- 

 menon*?" 



In these experiments I have had the advantage of the coope- 

 ration and assistance of Mr. M'Eniry, who also carried out all 

 the experiments which the late Sir 0. Wheatstone made on the 

 subject of his mercury receiver. 



London, October 6, 1876. 



2K2 



