Pyrometer

An instrument for determining the pre ure of fired gunpowder by the registered compre ion of oil,—invented by Dr. W. E. Wood bridge, and used by him and Maj. Mordecai (U. S. Ordnance Department) in experiments at Washington Arsenal, 1854-55. It consists of a small hollow steel cylinder filled with oil and a piston which is pre ed inwards upon the oil by the powder gases. The piston has a small stem projecting inwards, which is guided by a tube in the bottom of the cylinder. A steel point pre es against the stem and scratches a line upon it, when the piston is moved. The pyrometer is received by a hollow screw-plug placed in the side of the gun at the point where the pre ure is to be taken. This instrument is probably the most accurate and delicate one ever invented for the purpose. In the experiments it recorded certain vibrations in the column of gases, which have been generally neglected by theorists on the subject, but which are of great importance to the life of the gun. It seems unfortunate that an instrument which promised so much should have been allowed to fall into disuse, if not almost oblivion.