A current meter in which the current is determined by the amount of
chemical decomposition which it can effect. In the Edison meter the
solution is one of zinc sulphate. Two electrodes of zinc are immersed in
it, and a fractional part of the current is passed through it. The gain
in weight of one electrode and the loss in the other are proportional to
the current. Both electrodes are weighed periodically, one acting as
check upon the other.