The two heads are four inches in length, one inch of which is provided
with a screw thread. Each of them contains an aperture, c, 1.34 inches
wide below, 1.3 inches wide above, and 1.18 inches deep. This aperture
is followed by another and conical one, d, 1.38 inches deep, and 0.4
inch wide at its narrowest end, and finally by another one, e, 0.4 inch
wide, which runs to the exterior. The median piece, a, is 4 inches long.
It is provided at the two sides with nuts, between which there is a
cylindrical space, f, 1.8 inches long, designed to receive the charge.
The inflaming plug, g, is screwed into the exact center of the median
piece, a, which it enters to a depth of one inch. Into the space that
still remains free is screwed a plug, h. The lower surface of the plug,
g, contains a hollow space, 0.6 inch wide and deep. This hollow is
prolonged by another one, 0.24 inch wide, and contains a valve, i, which
has a play of about 0.08 inch. The three parts are connected by a key
which passes into the holes, x, and are rendered tight by copper rings,
y.

When it is desired to charge the apparatus, a leaden cylinder, 1.34
inches long and 1.3 inches in diameter, is placed in one of the heads,
and the median piece is so screwed that it can be made still tighter by
a few turns. Then a steel plate, k, 1.3 inches wide by 0.2 inch thick,
is placed against the cylinder, and against this plate again is placed a
cardboard disk, 1.34 inches wide by 0.4 inch thick. This completely
closes the hollow space. The steel plates and heads are marked with the
figures 1 and 2, which, through the pressure, are impressed upon the
leaden cylinders. Then the charge of powder, weighing exactly 300
grains, is introduced, and a new cardboard disk, a steel plate, and a
leaden cylinder are inserted, and the second head is screwed up. The
apparatus is now ready to operate. An ordinary priming is placed on the
pyramid, h, and the plug with the valve is screwed down in such a way