110 
MR. DANIELL ON VOLTAIC COMBINATIONS. 
brought into contact. If we take a second cell charged in the same way, and con- 
nect together the two zinc plates and the two platina, all is quiescent. No current 
can circulate, because the tendency of the generating plate in one cell to originate 
such a current in one direction of the circuit, is opposed by an equal tendency of the 
generating plate of the other to form one in the opposite direction. Substituting now, 
for the second cell, a third, charged with a solution of iodide of potassium and starch 
instead of the acidulated water, although it is easy to demonstrate that there is a similar 
tendency to form an opposing current, yet the current originating from the higher 
affinities of the first cell is sufficient to overcome that from the weaker affinities of the 
last cell, and iodine is abundantly precipitated upon the platinum plate of the latter, 
and immediately detected by the deep blue colour. Again, detaching the last cell, 
and connecting together its two plates in single circuit, its own current is esta- 
blished in the opposite direction, and the blue colour of the iodine speedily disappears 
from the platinum plate, under the influence of the hydrogen, which now takes its 
place. Thus your fundamental proof of the non-necessity of the contact of dissimilar 
metals for the establishment of an electric current is rendered very apparent and 
striking. 
Recurring again to the two cells similarly charged with acidulated water, if instead 
of connecting them by their two platinum and their two zinc plates, we connect each 
platinum with the zinc plate of the other, the direction of the currents from both 
generating plates will coincide, and each, instead of opposing, will assist the other ; 
and the completion of the circuit will be manifested by the evolution of gas in both 
the collecting jars. 
I began my series of experiments by charging each cell with water acidulated 
with sulphuric acid alone, in the proportion which I have just stated ; and upon con- 
necting them in single circles I found that the amount of action of each, as mea- 
sured by the quantity of hydrogen collected in their respective voltameters, in equal 
times, differed very materially, notwithstanding the apparent similitude of their cir- 
cumstances. The difference between the highest and the lowest was nearly a third ; 
and the inequality may probably be ascribed, partly to slight differences in the di- 
stances of the generating and conducting plates which it was not easy to avoid, and 
partly to differences in the amalgamated surfaces. Upon connecting them altogether 
in a single circular series, the inequalities disappeared : the amount of gas from each 
was equal, but was found to have fallen to that from the weakest cell. 
The circular arrangement of the cells of the battery, fig. 2., admits of their being 
combined together in various ways with the greatest facility by means of small cups 
of mercury (g, //, i) placed at proper intervals. My next disposition was to connect 
all the platinum plates together by wires radiating from them to a central cup (k) 
of mercury, and all the zinc plates by wires dipping into a ring of the same metal 
placed in a groove (ah cdef) surrounding the whole arrangement. In this state of 
things no action was of course manifest, for there was no complete circuit; but upon 
