constructed for civil uses, although such are no less
necessary than the others. Mr. D'O. Guttman has examined the principal
types of dynamometers with respect to their use for testing explosive
materials, and, after ascertaining wherein they are defective, has
devised an apparatus in which the principle is the same as that employed
by Messrs. Montluisant and Reffye at Meudon, that is to say, one in
which the force of the powder is made to act upon a lead cylinder fixed
in a conical channel. Mr. Desortiaux objects that in this system, when
it is employed with charges for cannons, the action has already begun
when only a portion of the powder is burned. To this, Mr. Guttman
responds that his apparatus operates only with small charges (300
grains), which practically inflame simultaneously in every part when the
igniting is done in a closed space. In order that the force may not be
made to act in one direction only, the inventor uses two leaden
cylinders. His apparatus is shown in the accompanying Figs. 1, 2, and 3.
It consists of a median piece, a, and of two heads, b, of an external
diameter of four inches. These pieces are of tempered Bessemer steel.
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