stamp; a demagnetizing collar moving freely in vertical guides and
provided with jaws placed so that the lugs of the chain may engage them;
a steel weight sliding loosely in vertical guides and drawn by the
demagnetizing collar to determinable heights when the machine is in
operation; a second demagnetizing collar, which may be set at known
heights, and provided with a release for the jaws of the first collar;
and a recording device geared to a vertically-driven threaded rod which
raises or lowers, sets the second demagnetizing collar, and thus
determines the height of fall of the weight. By this apparatus the
weight may be lifted to different known heights, and dropped on the
steel stamp which transmits the shock to the explosive. The fall
necessary to explode the sample is thus determined.

The hammers are of varying weight, the one generally used weighing
2,000 grammes. As the sensitiveness of an explosive is influenced by
temperature changes, water at 25° cent. is allowed to flow through the
anvil in order to keep its temperature uniform.

_Flame Test._--An apparatus, Fig. 2, Plate VIII, designed to measure
the length and duration of flames given off by explosives, is placed at
the northeast corner of Building No. 17. It consists essentially of a
cannon, a photographing device, and a drum geared for high speed, to
which a sensitized film may be attached.

About 13 ft. outside the wall of Building No. 17, set in a concrete
footing, is a cannon pointing vertically into an encasing cylinder or
stack, 20 ft. high and 43 in. in diameter. This cannon is a duplicate of
the one used for the ballistic pendulum, details of which have already
been given. The stack or cylinder is of ¼-in. boiler plate, in
twenty-four sections, and is absolutely tight against light at the base