488 Mr. 1\. Sabine'- on the Motions produced 



Mr. Gabriel [Lippmann *, in his paper " On the Connexion 

 between Capillary and Electrical Phenomena," ascribes the 

 electricity which lie observed to be. disengaged by a mercury 

 surface in acid water, advancing in a capillary tube, to a cliange 

 in its capillary constant, without, however, adducing any colla- 

 teral evidence. It appears to me that the electricity in ques- 

 tion may be accounted for by different states of oxidation of 

 the advancing and receding surfaces. So far, I have not found 

 a single experiment to indicate this assumed connexion between 

 capillary constant and disengaged electricity. That its oxi- 

 dized state modifies the surface-tension of mercury I will 

 show further on ; that it also modifies the electropositive state 

 of the surface is evident from the foregoing ; and two things, 

 both which depend upon a third, might have some propor- 

 tionality between them. But there does not appear to be any 

 nearer connexion, if this, between electricity and capilla- 

 rity of mercury ; and it is, I venture to suggest, premature 

 to call a difference of electrical potential produced in this way, 

 " polarization by capillary forces," until at least the " capil- 

 lary forces " in question have been more closely interrogated. 



II. Motions produced in Mercury hy Deoxidation. 



The following may be taken as representative of a class of 

 similar phenomena which have been made known by different 

 observers. When mercury is poured into a flat dinner-plate 

 to a depth of a quarter of an inch, and Fig. 4. 



a drop of water placed upon it, the drop, 

 as is well known, assumes an arched 

 section (a, fig. 4). If now the mer- 

 cury be connected with the zinc pole 

 and the drop by means of a fine plati- 

 num wire with the copper pole of a 

 battery of two or three elements, the 

 drop will contract and become more 

 spherical, as in b. "When the battery- 

 circuit is interrupted, the drop of water 



resumes its original form («). If the battery-current be re- 

 versed so that the copper pole is connected with the mercury 

 and the zinc pole with the drop, the latter gradually expands 

 as in c, whilst the mercury surface seen through the water be- 

 comes clouded with a slight film of suboxide. Reversing 

 again the battery, destroys the film and contracts the drop. 



Two views have been hitherto accepted by physicists as ex- 

 planatory of these phenomena. The first is that given by 

 Erman in his paper already cited, viz. that the reduction of 



* Pogg. Ann. vol. cxlix. p. 54G ; Phil. Mag. [IV.] vol. xlvii p. 281. 



