s of communication, the current of the whole of the battery, or of any
portion of it, could be made to pass through the instrument for given
portions of time in succession. The whole of the battery evolved 0.9 of a
cubic inch of oxygen and hydrogen in half a minute; the forty plates
evolved 4.6 cubic inches in the same time; the whole then evolved 1 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
sufficiently show the extremely injurious effect produced by the mixture of
strong and weak charges in the same battery[A].

[A] 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.

1045. 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
(1011.), 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.

1046. 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 (1011-1018.); 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 neutralizes the power of the
whole.

1047. 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 effec