On the Active Battery
plates evolved 4.6 cubic inches in the same time; the whole
then evolved i cubic inch in the half minute; the ten weakly
charged evolved 0.4 of a cubic inch in the time given: and
finally the whole evolved 1.15 cubic inch in the standard time.
The order of the observations was that given: the results suffi-
ciently show the extremely injurious effect produced by the
mixture of strong and weak charges in the same battery.1
 781.	In the same manner associations of strong and weak
pairs of plates should be carefully avoided.   A pair of copper
and platina plates arranged in accordance with a pair of zinc
and platina plates in dilute sulphuric acid, were found to stop
the action of the latter, or even of two pairs of the latter,, as
effectually almost as an interposed plate of platina (747); or
as if the copper itself had been platina.    It, in fact, became an
interposed decomposing plate, and therefore a retarding instead
of an assisting pair.
 782.	The reversal) by accident or otherwise, of the plates in
a battery has an exceedingly injurious effect.   It is not merely
the counteraction of the current which the reversed plates can
produce, but their effect also in retarding even as indifferent
plates, and requiring decomposition to be effected upon their
surface, in accordance with the course of the current, before the
latter can pass.   They oppose the current, therefore, in the
first place, as interposed platina plates would do (747-754);
and to this they add a force of opposition as counter-voltaic
plates.    I find that, in a series of four pairs of zinc and platina
plates in dilute sulphuric acid, if one pair be reversed, it very
nearly neutralises the power of the whole.
 783.	There are many other causes of reaction, retardation,,
and irregularity in the voltaic battery.    Amongst them is the'
not unusual one of precipitation of copper upon the zinc in the
cells, the injurious effect of which has before been adverted to
(742).   But their interest is not perhaps sufficient to justify
any increase of the length of this paper, which is rather intended
to be an investigation of the theory of the voltaic pile than a
particular account of its practical application.
Note.—Many of the views and experiments in this part of
my Experimental Researches will be seen at once to be correc-
tions and extensions of the theory of electro-chemical decom-
1 The gradual increase in the action of the whole fifty pairs of plates was
due to the elevation of temperature in the weakly charged trough by the
passage of the current, in consequence of which the exciting energies of the
fluid within were increased.