96 
MR. GROVE ON THE GAS VOLTAIC BATTERY. 
rent, but would also tend to diminish the hydrogen. As this last is totally indepen- 
dent of the general action, it could be abstracted by merely placing a cell charged 
similarly to the battery out of the circuit with the terminals unconnected as in fig. 1 ; 
in a cell so placed the hydrogen was found to be absorbed in the ratio of rather less 
than 0*1 cubic inch in twenty-four hours. 
On some occasions I found the rise of liquid in the hydrogen cell to be unequal in 
different tubes of the battery, and this I found more particularly the case in the bat- 
tery fig. 4 ; it was some time before I discovered the cause of this. I will not enu- 
merate my different conjectures, but state that which proved to be the correct one. 
As, in using the two forms of batteries (figs. 1 and 4), the chief difference consisted in 
the introduction of the finger, it occurred to me that my assistant’s hands, which 
were employed in various manipulations, might, in placing the tubes in the cells of 
fig. 4, introduce into the electrolyte small portions of foreign matter, particularly 
metals, and that thus a local action might be occasioned ; this view was strengthened 
by my frequently observing copper deposited upon some of the immersed portions of 
the platinum, and where this happened an excess of hydrogen was generally found 
to have been absorbed : to examine the accuracy of this view I caused 
Experiment 2, — Four cells to be charged with a solution of sulphate of copper, and 
connected in closed circuit ; after twenty-four hours’ work, the liquid in the oxygen 
and hydrogen tubes had risen equally in three of the pairs, but in the fourth the 
liquid in the hydrogen tube had risen rather more than twice as high as in any of 
the others, and the whole of the platinum in this tube, from the water- mark down- 
wards, was covered with metallic copper; it was thus evident that a slight precipita- 
tion having commenced on this platinum from some local circumstance which offered 
less resistance in this cell than in the others, a separate local current had been esta- 
blished, the hydrogen and the copper acting as a voltaic circuit, fresh copper had 
been constantly deoxidated at the expense of the hydrogen : the phenomenon is per- 
fectly analogous to that observable in an ordinary sulphate of copper battery, when 
a slight portion of copper is deposited upon the zinc, and a local current is established 
by which the zinc is worn into a hole without contributing to the general current. 
I have been thus particular in order to explain points in the action of this battery 
which might seem exceptions to the law of definite electrolysis, or what perhaps we 
should here call electro-synthesis ; as a general result, the equivalent action of the 
battery was very beautiful ; with fifty cells in action there was but a trifling difference 
in the rise of liquid in all the cells, and the rise of gas in the voltameter appeared so 
directly proportional, that an observer unacquainted with the rationale of a voltaic 
battery, would have said the gases from the exterior cells of the battery were con- 
veyed through the solid wires and evolved in the voltameter ; and had this been the 
first voltaic battery ever invented, this probably would have been the theory of its 
action. 
In my original paper, I considered the points of voltaic action to be those where 
