GAUGES, PRESSURE

instruments which indicate or measure the pre ure of fluids (either liquids or gases). They are of three types: (1) The liquid column or manometer type, used for accurate scientific measurement; in this the pre ure is indicated by the height to which it will force a column and liquid of known specific gravity, in a tube. Light oils, water or mercury are used, depending upon the pre ure to be measured. (2) The Bourdon Spring type, the most practical and extensively used gauge. This consists of a thin metal tube of elliptical section, bent into the arc of a circle. One end is sealed, and attached through links to a pointer which indicates the pre ure on a scale, the other connects with the container in which the pre ure is to be measured. When the pre ure inside the tube is greater than that of the atmosphere surrounding it, the tube tends to change its cro -section to a circular one, this effects a straightening of the tube, thus changing the position of the pointer and registering an increased pre ure. (3) That type which depends for its indication on the compre ion of a spring when acted upon by a piston upon which the pre ure manifests itself. town, A am, India, on Brahmaputra. Pop. 11,500.