Source : Webster's Revised Unabridged Dictionary (1913)

Boiler \Boil"er\, n.
   1. One who boils.

   2. A vessel in which any thing is boiled.

   Note: The word boiler is a generic term covering a great
         variety of kettles, saucepans, clothes boilers,
         evaporators, coppers, retorts, etc.

   3. (Mech.) A strong metallic vessel, usually of wrought iron
      plates riveted together, or a composite structure
      variously formed, in which steam is generated for driving
      engines, or for heating, cooking, or other purposes.

   Note: The earliest steam boilers were usually spheres or
         sections of spheres, heated wholly from the outside.
         Watt used the wagon boiler (shaped like the top of a
         covered wagon) which is still used with low pressures.
         Most of the boilers in present use may be classified as
         plain cylinder boilers, flue boilers, sectional and
         tubular boilers.

   {Barrel of a boiler}, the cylindrical part containing the
      flues.

   {Boiler plate}, {Boiler iron}, plate or rolled iron of about
      a quarter to a half inch in thickness, used for making
      boilers and tanks, for covering ships, etc.

   {Cylinder boiler}, one which consists of a single iron
      cylinder.

   {Flue boilers} are usually single shells containing a small
      number of large flues, through which the heat either
      passes from the fire or returns to the chimney, and
      sometimes containing a fire box inclosed by water.

   {Locomotive boiler}, a boiler which contains an inclosed fire
      box and a large number of small flues leading to the
      chimney.

   {Multiflue boiler}. Same as {Tubular boiler}, below.

   {Sectional boiler}, a boiler composed of a number of
      sections, which are usually of small capacity and similar
      to, and connected with, each other. By multiplication of
      the sections a boiler of any desired capacity can be built
      up.

   {Tubular boiler}, a boiler containing tubes which form flues,
      and are surrounded by the water contained in the boiler.
      See Illust. {of Steam boiler}, under {Steam}.

   {Tubulous boiler}. See under {Tubulous}. See {Tube}, n., 6,
      and 1st {Flue}.