Galvatilsm and Electro-magnetism. 163 



days, until the anode was nearly dissolved ; the colour of 

 the liquid became continually deeper, but the disengage- 

 ment of hydrogen, though it diminished in quantity, did not 

 cease. I think we may conclude from this experiment that in 

 secondary voltaic actions there is neither that simultaneity 

 of effect, nor that necessity of entering into combination or 

 of being disengaged from it, which has place in primary 

 electrolytic actions. 



During my experiments many anomalies respecting these 

 secondary actions have presented themselves which it would 

 be too embarrassing to describe here : in fact there is here 

 a void which it will be difficult to fill, because molecular forces 

 which as yet we know nothing of appear to play a most im- 

 portant part. 



With respect to the technical importance of these voltaic 

 copies, I would observe that we may use the engraved cathode, 

 not only of metals more negative than copper, but also of 

 positive metals and their alloys, (excepting brass,) notwith- 

 standing that these metals, &c. decompose the salts of copper 

 with too much energy when alone. Thus one may make, for 

 example, stereotypes in copper which may be multiplied as 

 much as we please. I shall shortly have the honour to send 

 you a bas-relief in copper, of which the original is formed of 

 a plastic substance, which adapts itself to all the wants and 

 caprices of art. By this process all those delicate touches 

 are preserved which make the principal beauty of such a 

 work, and which are usually sacrificed in the process of cast- 

 ing, a process which is not capable of reproducing them in 

 all their purity. Artists should be very grateful to galvanism 

 for having opened this new road to them. 



During the last winter I frequently illuminated my saloon, 

 which is of considerable size, by Drummond's light. The 

 mixed gases were obtained in sufficient quantities, that is to 

 say, at the rate of 3 or 4 cubic feet per hour, by decomposing 

 dilute sulphuric acid (specific gravity 1*33,) between electrodes 

 of platina by a constant battery of a particular construction. 

 I only passed the gas through a glass tube filled with chloride 

 of calcium, and there was neither gasometer nor any other 

 provision for it. As soon as the voltaic current was closed 

 the jet might be lighted, and the flame then burnt tranquilly, 

 and of the same intensity for any length of time. The construc- 

 tion and manipulation of the battery, though extremely per- 

 fect, was still a little embarrassing. At present, a battery, with 

 a decomposing apparatus which will produce from 3 to 4 

 cubic feet of electrolyzed gas per hour, occupies little more 

 space than the page of paper on which I write to you (10 



M2 



