substances to a very small relative weight.

The oxide of copper batteries have given interesting results in their
application to telephones. For theatrical purposes the same battery
may be employed during the whole performance, instead of four or five
batteries. Their durability is considerable; three elements will work
continuously, night and day, Edison's carbon microphones for more than
four months without sensible loss of power.

Our elements will work for a hundred hours through low resistances,
and can be worked at any moment, after several months, for example. It
is only necessary to protect them by a cover from the action of the
carbonic acid of the atmosphere.

We prefer potash to soda for ordinary batteries, notwithstanding its
price and its higher equivalent, because it does not produce, like
soda, creeping salts. Various modes of regeneration render this
battery very economical. The deposited copper absorbs oxygen pretty
readily by simple exposure to damp air, and can be used again. An
oxidizing flame produces the same result very rapidly.

Lastly, by treating the exhausted battery as an accumulator, that is
to say, by passing a current through it in the opposite direction, we
restore the various products to their original condition; the copper
absorbs oxygen, and the alkali is restored, while the zinc is
deposited; but the spongy state of the deposited zinc necessitates its
being submitted to a process, or to its being received upon a mercury
support. Again, the oxide of copper which we employ, being a waste
product of brazing and plate works, unless it be reduced, loses
nothing of its value by its reduction in the battery; the