Proceedings of the Royal Society. 257 
acid only. They consist in active motions of those particles of the 
acid in contact with the mercury, while the superficial molecules 
of the metal continually radiate from the point nearest the negative 
pole, and darting to the positive pole, return along the axis. The 
author particularly notices several singular appearances resulting 
from this current, and shews them to be independent of any electro- 
magnetic vortices, to which at first sight they present considerable 
analogy; they are incomparably more forcible in proportion to the 
electric powers used, than the motions produced by the action of 
magnets. Hence they furnish an extremely sensible test of the 
developement of feeble voltaic powers, not easily rendered sensible 
by other means. 
The author next describes the appearances observed in caseg 
where other liquids and metals are used, and adverts to the influ- 
ence of several causes upon the uniformity of the results. Among 
these, impurity in the mercury is especially noticed, which should 
not only be carefully distilled, but also well washed with dilute 
nitric acid. Mercury thus purified, and placed in the circuit as 
before, exhibits phenomena varying with the nature of the liquid. 
Generally speaking, currents are produced radiating from the 
point nearest the negative pole, which are most violent in acids? 
-and less in saline solutions, in proportion as the electro-positive 
energy of the base is greater. In many liquids a counter current 
from the positive pole is observed ; but if either pole be brought into 
‘contact with the mercury, no currents are observed from the point 
of contact, but strong ones are perceived to radiate from the other, 
If the negative pole touch, it amalgamates with the mercury, 
which remains bright; if the positive pole, the mercury rapidly 
oxidizes, and in both cases currents are produced. 
Mr. H. proceeds to observe, that when mercury is electrized in 
saline solutions, its properties are generally altered, and he de- 
scribes at length the phenomena thus presented in a solution of 
sulphate of soda, which were peculiar and apparently. perplexing, 
but which he found to depend upon the presence of amalgam of 
sodium, counteracting the effect of the negative pole, and exalting 
that of the positive in propoytion to its quantity, until it overcomes 
