GAUGE (from OF. gauge, jauge; connected with ML. gaugatum, gauging of a wine-cask, jalagium, right to gauge wine-casks, and prob ably with plea, gallon, OF., Fr. jale, bowl). In mechanics, an instrument for determining the dimensions, quantity, force, capacity, etc., of anything. Gauges are of various forms, and are employed for numerous purposes in engi neering and the arts. Gauges to secure precision in the dimensions and forms of manufactured articles are made of hardened steel, or of case hardened wrought iron, formed to the exact out line to be secured and accurately dimensioned. Such gauges are extensively used in machinery manufacture where interchangeability of corre sponding parts is sought. Wire gauges are cir cular disks of hardened steel, having round the edge a series of notches of different sizes of openings corresponding to the standard wire sizes of the Birmingham or other gauges. In the Birmingham wire gauges the sizes run from No. 1, denoting a wire diameter of 0.3 inch, to No. 34, denoting a wire diameter of 0.004 inch. Similar gauges are used for measuring the thickness of metal plates. Pressure-gauges for measuring the pressure of steam or other gas inside a closed vessel are familiar to all. In the most usual form the pressure of the gas acts to cause a pointer to move around a graduated dial. The steam-boiler gauge is a familiar ex
ample of such devices. Wind-gauges are ar rangements by which the wind blowing against a plate diaphragm actuates a recording device which records the pressure. (See ANEMOME TER.) Water-gauges consist of a strong glass tube with metal fixtures at its ends, which con nect the tube with the interior of a steam boiler. The lower end of the tube connects with the boiler below the lowest water-line, and the upper end connects with it above the highest water line, and the level of the water between the two points is observable by the height at which it stands in the glass. Screw-gauges consist of a U-shaped frame of steel at the end of one arm of which is a steel plug pointing toward the opposite arm, through whose end runs a finely threaded thumb-screw with a graduated head. To measure with this device the end of the plug is brought into contact with one side of the object, and the screw run out into it touches the other side; a reading of the graduated head shows the distance apart of the end of the plug and the end of the screw, and therefore the thickness of the object. See CALIPERS; RAILWAYS.