Eprouvette

( Fr. ). A small mortar to prove the strength of gunpowder. There are different sorts of eprouvettes, according to the fancy of different nations who use them. Some raise a weight, and others throw a shot, to certain heights and distances. As a test of gunpowder the eprouvette is comparatively worthle , and it has been generally superseded by instruments for measuring the initial velocity obtained by firing the powder in the particular gun for which it is intended. A short mortar is, however, still used, to a certain extent, for testing the power of modern blasting powders, such as the mixtures of nitro-glycerine. A very small charge and a heavy shot of chilled iron which enters two or three inches only into the mortar are used. The square roots of the ranges (other things being equal) give the relative powers of the different powders, nearly.