late, 100 ft. long and more than 6 ft. in diameter, solidly attached to a mass of concrete at one end, in which is embedded a cannon from which to discharge the explosive under test, and open at the other end, and otherwise so constructed as to simulate a small section of a mine gallery (Fig. 2, Plate VI). The heavy mortar pendulum, for the pendulum test for determining the force produced by an explosive, is near by, as is also an armored pit in which large quantities of explosive may be detonated, with a view to studying the effects of magazine explosions, and for testing as to the rate at which ignition of an explosive travels from one end to the other of a cartridge, and the sensitiveness of one cartridge to explosion by discharge of another near by.
[Illustration: PLATE VI.
Fig. 1.--Explosion from Coal Dust in Gas and Dust Gallery No. 1.
Fig. 2.--Mine Gallery No. 1.
Fig. 3.--Ballistic Pendulum.]
In another building (No. 21), is a well-equipped chemical laboratory for che