TRANSACTIONS OF THE SECTIONS. - 45 
_ Observations on the Crystallization of Metals by voltaic action, inde- 
pendent of the proximity of metallic electrodes. By Goiv1nc Brrp, 
= MD. PLS. F.GS., Lecturer on Experimental Philosophy at 
Guy's Hospital, sc. 
It is well known that one of the latest discoveries on the conditions 
of electrolytic action has been to observe, that the presence of metallic 
or solid electrodes was not necessary to the production and perfection 
_ of true polar decomposition ; this fact among a host of others with 
_ which that philosopher has enriched science, was announced by our 
illustrious countryman Dr. Faraday. 
Results depending on the same principle occurred to the author 
_ whilst engaged in a series of experiments on the electrolytic energy of 
electric currents of feeble tension, some of which have been described 
_ ima paper read before the Royal Society of London, in February 1837, 
and since inserted in the “ Philosophical Transactions,” and appeared 
to partake of perhaps more than ordinary interest, from the very feeble 
intensity of the voltaic current required for their success, as well as 
from their analogy to what, perhaps, is going on in the great laboratory 
 ofnature, in effecting the reduction and crystallization of metals. The 
voltaic apparatus used consists of an exceedingly simple arrangement :—a 
cylinder of glass, about 8 inches in height and two inches in diameter, 
forms the exterior vessel or cell of the battery; immersed in this, is a 
second cylinder, 4 inches in height, and about 1°5 inch in diameter, 
- open at both ends; a plug of plaster of Paris, about 2 inches thick, is 
made to fit its lower half accurately, by being poured in whilst as thin 
as cream, forming, on its becoming solid, a firm but porous base to the 
cylinder. The external cylinder is then filled with a weak solution of 
common salt (chloride of sodium), whilst the internal cylinder is filled 
_ with a solution of a metallic salt, (as sulphate of copper,) which be- 
_ coming rapidly imbibed by the porous plug of plaster of Paris, comes 
__ in contact with the brine in the exterior vessel, without, however, causing 
their intermingling rapidly. A plate of polished copper soldered to a 
_ thick wire or ribbon of the same metal is then plunged into the solution 
of the sulphate of copper, whilst a plate of zinc connected to the other 
_ end of the copper wire is immersed in the solution of common salt. Under 
_ these circumstances it is obvious that an electric current becomes de- 
_ veloped, the positive fluid escaping from the copper to the zine along 
_ the connecting wire, back through some inches of brine to the plaster 
_ of Paris plug, thence to the copper solution, which it has to penetrate 
before it can gain the copper plate which serves for the negative elec- 
_ trode. The zinc plate becoming electro-positive determines the decom- 
position of the water, uniting with its oxygen to form oxide of zinc, 
_ which uniting with the hydrochloric acid of the common salt sets the 
_ positive elements, hydrogen and soda, at liberty, determining their 
_ evolution at the negative electrode; they, however, in their passage 
__ effect the decomposition of the sulphate of copper and cause the pre- 
_ cipitation of metallic crystals on the copper plate; or we may suppose 
that in the first instance the zine plate effects the decomposition of the 
