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}.