[Illustration: FIG. 1.--SIMPLE BATTERY.]

Between the zinc plate and the wooden bar adjoining it is inserted a
strip of copper, c, for leading away the current from the zinc pole of
the battery, and between the carbon plates and the wooden bars is
inserted a doubled strip of copper, d, forming a connection between
the two carbon plates, and at the same time serving as a conductor for
conveying away the current from the carbon pole of the battery. This
element is to be plunged into a tumbler of sufficient depth to allow
the wooden bars to rest on the upper edge of the tumbler, while the
lower ends of the plates are one-half or three-quarters inch above the
tumbler bottom.


THE SOLUTION.

In the tumbler is placed a solution consisting of two-thirds of a
tumblerful of water, two ounces of bichromate of potash, and two
ounces of sulphuric acid. The bichromate of potash should be dissolved
first, then the acid should be slowly and carefully added. As the
solution heats, it is well to prepare it in an earthen vessel, which
is not liable to break. These materials should be used with great
caution, as they are poisonous, and the solution is very corrosive,
destroying almost everything with which it comes in contact. With
proper care, however, there is no danger in using the solution. It
gives off no poisonous vapors. Of course it is advisable to make the
solution in quantities of a gallon or so when convenient.

The battery compound known as the C and C battery compound, sold in