Si·phon n.
 1. A device, consisting of a pipe or tube bent so as to form two branches or legs of unequal length, by which a liquid can be transferred to a lower level, as from one vessel to another, over an intermediate elevation, by the action of the pressure of the atmosphere in forcing the liquid up the shorter branch of the pipe immersed in it, while the continued excess of weight of the liquid in the longer branch (when once filled) causes a continuous flow. The flow takes place only when the discharging extremity of the pipe ia lower than the higher liquid surface, and when no part of the pipe is higher above the surface than the same liquid will rise by atmospheric pressure; that is, about 33 feet for water, and 30 inches for mercury, near the sea level.
 2. Zool. (a) One of the tubes or folds of the mantle border of a bivalve or gastropod mollusk by which water is conducted into the gill cavity. See Illust. under Mya, and Lamellibranchiata. (b) The anterior prolongation of the margin of any gastropod shell for the protection of the soft siphon. (c) The tubular organ through which water is ejected from the gill cavity of a cephaloid. It serves as a locomotive organ, by guiding and confining the jet of water. Called also siphuncle. See Illust. under Loligo, and Dibranchiata. (d) The siphuncle of a cephalopod shell. (e) The sucking proboscis of certain parasitic insects and crustaceans. (f) A sproutlike prolongation in front of the mouth of many gephyreans. (g) A tubular organ connected both with the esophagus and the intestine of certain sea urchins and annelids.
 3. A siphon bottle.
 Inverted siphon, a tube bent like a siphon, but having the branches turned upward; specifically Hydraulic Engineering, a pipe for conducting water beneath a depressed place, as from one hill to another across an intervening valley, following the depression of the ground.
 Siphon barometer. See under Barometer.
 Siphon bottle, a bottle for holding aerated water, which is driven out through a bent tube in the neck by the gas within the bottle when a valve in the tube is opened; -- called also gazogene, and siphoid.
 Siphon condenser, a condenser for a steam engine, in which the vacuum is maintained by the downward flow of water through a vertical pipe of great height.
 Siphon cup, a cup with a siphon attached for carrying off any liquid in it; specifically Mach., an oil cup in which oil is carried over the edge of a tube in a cotton wick, and so reaches the surface to be lubricated.
 Siphon gauge. See under Gauge.
 Siphon pump, a jet pump. See under Jet, n.


 Gauge, n.
 1. A measure; a standard of measure; an instrument to determine dimensions, distance, or capacity; a standard.
    This plate must be a gauge to file your worm and groove to equal breadth by.   --Moxon.
    There is not in our hands any fixed gauge of minds.   --I. Taylor.
 2. Measure; dimensions; estimate.
    The gauge and dimensions of misery, depression, and contempt.   --Burke.
 3. Mach. & Manuf. Any instrument for ascertaining or regulating the dimensions or forms of things; a templet or template; as, a button maker's gauge.
 4. Physics Any instrument or apparatus for measuring the state of a phenomenon, or for ascertaining its numerical elements at any moment; -- usually applied to some particular instrument; as, a rain gauge; a steam gauge.
 5. Naut. (a) Relative positions of two or more vessels with reference to the wind; as, a vessel has the weather gauge of another when on the windward side of it, and the lee gauge when on the lee side of it. (b) The depth to which a vessel sinks in the water.
 6. The distance between the rails of a railway.
 Note: ☞ The standard gauge of railroads in most countries is four feet, eight and one half inches. Wide, or broad, gauge, in the United States, is six feet; in England, seven feet, and generally any gauge exceeding standard gauge. Any gauge less than standard gauge is now called narrow gauge. It varies from two feet to three feet six inches.
 7. Plastering The quantity of plaster of Paris used with common plaster to accelerate its setting.
 8. Building That part of a shingle, slate, or tile, which is exposed to the weather, when laid; also, one course of such shingles, slates, or tiles.
 Gauge of a carriage, car, etc., the distance between the wheels; -- ordinarily called the track.
 Gauge cock, a stop cock used as a try cock for ascertaining the height of the water level in a steam boiler.
 Gauge concussion Railroads, the jar caused by a car-wheel flange striking the edge of the rail.
 Gauge glass, a glass tube for a water gauge.
 Gauge lathe, an automatic lathe for turning a round object having an irregular profile, as a baluster or chair round, to a templet or gauge.
 Gauge point, the diameter of a cylinder whose altitude is one inch, and contents equal to that of a unit of a given measure; -- a term used in gauging casks, etc.
 Gauge rod, a graduated rod, for measuring the capacity of barrels, casks, etc.
 Gauge saw, a handsaw, with a gauge to regulate the depth of cut. --Knight.
 Gauge stuff, a stiff and compact plaster, used in making cornices, moldings, etc., by means of a templet.
 Gauge wheel, a wheel at the forward end of a plow beam, to determine the depth of the furrow.
 Joiner's gauge, an instrument used to strike a line parallel to the straight side of a board, etc.
 Printer's gauge, an instrument to regulate the length of the page.
 Rain gauge, an instrument for measuring the quantity of rain at any given place.
 Salt gauge, or Brine gauge, an instrument or contrivance for indicating the degree of saltness of water from its specific gravity, as in the boilers of ocean steamers.
 Sea gauge, an instrument for finding the depth of the sea.
 Siphon gauge, a glass siphon tube, partly filled with mercury, -- used to indicate pressure, as of steam, or the degree of rarefaction produced in the receiver of an air pump or other vacuum; a manometer.
 Sliding gauge. Mach. (a) A templet or pattern for gauging the commonly accepted dimensions or shape of certain parts in general use, as screws, railway-car axles, etc. (b) A gauge used only for testing other similar gauges, and preserved as a reference, to detect wear of the working gauges. (c) Railroads See Note under Gauge, n., 5.
 Star gauge Ordnance, an instrument for measuring the diameter of the bore of a cannon at any point of its length.
 Steam gauge, an instrument for measuring the pressure of steam, as in a boiler.
 Tide gauge, an instrument for determining the height of the tides.
 Vacuum gauge, a species of barometer for determining the relative elasticities of the vapor in the condenser of a steam engine and the air.
 Water gauge. (a) A contrivance for indicating the height of a water surface, as in a steam boiler; as by a gauge cock or glass. (b) The height of the water in the boiler.
 Wind gauge, an instrument for measuring the force of the wind on any given surface; an anemometer.
 Wire gauge, a gauge for determining the diameter of wire or the thickness of sheet metal; also, a standard of size. See under Wire.

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