Siphon barometer

Siphon \Si"phon\, n. [F. siphon, L. sipho, -onis, fr. Gr. ??? a
   siphon, tube, pipe.]
   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.
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   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.
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   3. A siphon bottle.
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   {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.
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Barometer \Ba*rom"e*ter\, n. [Gr. ba`ros weight + -meter: cf. F.
   barom[`e]tre.]
   An instrument for determining the weight or pressure of the
   atmosphere, and hence for judging of the probable changes of
   weather, or for ascertaining the height of any ascent.
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   Note: The barometer was invented by Torricelli at Florence
         about 1643. It is made in its simplest form by filling
         a graduated glass tube about 34 inches long with
         mercury and inverting it in a cup containing mercury.
         The column of mercury in the tube descends until
         balanced by the weight of the atmosphere, and its rise
         or fall under varying conditions is a measure of the
         change in the atmospheric pressure. At the sea level
         its ordinary height is about 30 inches (760
         millimeters). See {Sympiesometer}. --Nichol.
         [1913 Webster]

   {Aneroid barometer}. See {Aneroid barometer}, under
      {Aneroid}.

   {Marine barometer}, a barometer with tube contracted at
      bottom to prevent rapid oscillations of the mercury, and
      suspended in gimbals from an arm or support on shipboard.
      

   {Mountain barometer}, a portable mercurial barometer with
      tripod support, and long scale, for measuring heights.

   {Siphon barometer}, a barometer having a tube bent like a
      hook with the longer leg closed at the top. The height of
      the mercury in the longer leg shows the pressure of the
      atmosphere.

   {Wheel barometer}, a barometer with recurved tube, and a
      float, from which a cord passes over a pulley and moves an
      index.
      [1913 Webster] Barometric