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might be likened to the fire, and the copper to a hand which
dips into the cell to pick up the current and takes no part
chemically. '

If a wire is connected to each of the plates and the free
ends of the wires touched to the tip of the tongue it will
produce a peculiar salty taste in the mouth indicating the
presence of a current of electricity.

If the wires are connected to an electric bell, the bell will
ring, or, instead, the current may be used to run a small
motor. If the cell is made of two zinc plates or two copper
plates, the bell will not ring, because no electricity will be
produced. In order to produce a current, the electrodes
must be made of two different materials upon which the
acid acts differently. Current may be obtained from a cell
made with a zinc and carbon plate or from one with zinc and

Therefore, in order to make a battery it is necessary 'to
have a metal which may be consumed, a chemical to con-
sume or oxidize it, and an inactive element which is merely
present to collect the electricity.

When the wires connected to the two plates are- joined
together, a current of electricity will flow from the copper
plate through the wire to the zinc. The copper is known as
the positive pole and the zinc as the negative.

A simple voltaic cell may be easily made by cutting out a
strip of zinc and a strip of copper, each-3% inches long, and
one inch wide. A small hole bored through the upper end
of the strips will permit them to- be mounted on a wooden

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