46 SEVENTH REPORT—1837. 
common salt, as chloride of sodium, chloride of zine being formed, and 
sodium evolved, which, in its passage through the copper solution, 
effects its decomposition and reduction on the surface of the negative 
electrode. On either hypothesis the ultimate electrolytic action 
produced must be regarded as the secondary, and not as the primary 
and immediate effect of the voltaic current. The copper reduced on 
the surface of the negative electrode, is (as is well known) not brown 
and spongy, as when more intense currents are employed, but hard and 
crystalline as in native specimens, the crystals being frequently inter- 
mingled with those of the ruby-coloured protoxide, in which case their 
resemblance to the native mineral is most remarkable. 
After leaving an apparatus of this kind just described to itself for 
some months, the fluid in the interior cylinder had lost nearly all its 
blue colour, scarcely a trace of copper being present, it having become 
a tolerably pure solution of sulphate of soda; but on examining the 
surface of the copper-plate immersed in it, the quantity of reduced 
copper was found considerably less than one quarter of the quantity 
previously present in the sulphate. Dr. Bird, being unable satisfac- 
torily to account for this loss, was led to examine the contents of the 
cylinders with the greatest care; and on removing the plaster of Paris 
plug, which had now become quite soft, and lixiviating it with water, 
he had the pleasure of meeting with numerous, very hard, and beauti- 
fully defined crystals of metallic copper, imbedded in the thick- 
ness of the mass of sulphate of lime, not merely in scattered and 
isolated crystals, but in distinct and continuous veins. Some of 
these veins were distinctly visible without breaking up the mass of 
plaster, being spread in a curiously ramified manner, like the branches 
of a tree, on that part of the plaster in contact with the glass. These 
metallic crystals must have been reduced from that portion of the 
copper solution absorbed by the plug of sulphate of lime, simply by 
the passage of the current of electricity from one electrode to the 
other, notwithstanding no metallic, or even solid connection of any 
kind existed between the reduced crystals of copper and the negative 
electrode. The result of this experiment is therefore interesting, if it 
only serves to confirm the observation of Dr. Faraday, that the pre- 
sence of a solid electrode is by no means necessary for the perfection 
of electrolytic action, for we here see crystals of metallic copper pro- 
duced at a distance midway between the electrodes of metal, and at 
some inches from either. But this experiment is interesting in another 
and perhaps more important point of view, as it tends to throw some 
light on the mysterious and interesting process of the reduction of 
metals, and formation of metallic veins in the bowels of our earth. 
The author then showed the bearing of these results on the ques- 
tion of the influence of electrical currents in arranging the materials 
of mineral veins. 
If, in the apparatus above-described, a plate of clear lead is substi- 
tuted for one of copper, for the negative electrode, and a solution of 
acetate or nitrate of lead, for sulphate of copper, an electric current 
will of course be set in motion, and spangles of reduced lead will 
