The Gun and Ballistic pendulum, and Navez’ Electro-ballistic Machine. The latter is considered the best for determining the initial velocity.
87]
27. What is the hygrometric proof of powder?
Samples are placed in shallow tin pans, set in a tub, the bottom of which is covered with water; the pans should be about an inch above the water, and the tub covered. Good powder will not absorb more than 2½ per cent. in 24 hours.
28. How can the relative quickness of two kinds of powder be determined?
By burning a train laid in a circular or other groove, which returns into itself, made in a piece of hard wood: one-half of the groove being filled with each kind of powder, and fire communicated at the junction of the two trains, the relative quickness is readily deduced from observation of the point at which the flames meet.
29. What are the qualities of good powder?
It should be perfectly free from dust, uniform in strength and size of grains, angular and irregular in form; in color, brownish black, or slate color; so hard as not to be easily crushed by pressure with the finger; and should leave no beads or foulness when flashed in quantities of 10 grs. on a copper plate.
30. What is the expansive velocity, and pressure of ignited powder?
The expansive velocity is about 5,000 feet per second, and pressure about 2,000 atmospheres.