Powder Mine

A cave or hollow in which powder is placed to be fired at any particular time. These were first used in 1503 at Naples. Powder Pre — A machine for compre ing powder. In the pre ing proce , the powder that has pa ed through the breaking-down machine is taken to the pre -house, where it is compre ed into hard cake, for the purpose of fitting it to be made into a hard grain of equal density. twder-proof. — The proof of power used in proving ordnance. It should be tested immediately before being used and should give not le than the standard initial velocity. twer-plant. — In aviation, the entire apparatus for generating power on an aeroplane, including motor, propeller, radiator, gasoline tank, etc.