Eprouette

Eprouette is a machine for proving or testing the strength of gunpowder. The gun eprouette does this by measuring the amount of recoil produced on a small gun swung like a pendulum; the mortar eprouette by measuring the distance to which a ball is projected. A third pattern is shaped like a small pistol, with an extremely short barrel, closed by a flat plate connected with a strong spring. On firing, the plate is driven back to a distance indexed according to the strength of the powder.