lation of the potash, we
inclose a quantity of this substance in the solid state necessary for
an element in the box which receives the oxide of copper, and furnish
it with a cover supported by a ring of caoutchouc. It suffices then
for working the battery to open the box of potash, to place it at the
bottom of the jar, and to add water to dissolve the potash; we then
pour in the copper oxide inclosed in a bag.

We also form the oxide of copper very conveniently into blocks. Among
the various means which might be employed, we prefer the following:

We mix with the oxide of copper oxychloride of magnesium in the form
of paste so as to convert the whole into a thick mass, which we
introduce into metal boxes.

The mass sets in a short time, or very rapidly by the action of heat,
and gives porous blocks of a solidity increasing with the quantity of
cement employed (5 to 10 per cent.).

[Illustration: FIG. 2.]

Fig. 2 represents an arrangement with blocks. The jar V, is provided
with a cover of copper, E, screwing into the glass. This cover carries
two vertical plates of sheet-iron, A, A', against which are fixed the
prismatic blocks, B, B, by means of India rubber bands. The terminal,
C, carried by the cover constitutes the positive pole. The zinc is
formed of a single pencil, D, passing into a tube fixed to the center
of the cover. The India rubber, G, is folded back upon this tube so as
to make an air-tight joint.

The cover carries, besides, another tube, H, covered by a split
India-rubber tube, which forms a safety valve.

The closing is made hermetical by means of an India rubber tube, K,
which presses against the glass and the cover. The potash to charge
the element is in pieces, and is contained either in the glass jar
itself or in a separate box of sheet-iron.

Applying the same arrangement, we form hermetically sealed elements
with a single plate of a very small size.

The employment of cells of iron, cast-iron, or copper, which are not
attacked by the exciting liquid, allows us to easily construct
elements exposing a large surface (Fig. 3).

[Illustration: FIG. 3.]

The cell, A, forming the positive pole of the battery is of iron plate
brazed upon vertical supports; it is 40 centimeters long by 20
centimeters wide, and about 10 centimeters high.

We cover the bottom with a layer of oxide of copper, and place in the
four corners porcelain insulators, L, which support a horizontal plate
of zinc, D, D