[Illustration: Fig. 11.]

Figs. 9, 10, and 11 represent a marine tubular boiler; fig. 9 being a
vertical longitudinal section, fig. 10 half a front elevation and half a
transverse section, and fig. 11 half a back elevation and half a transverse
section near the end. There is a projecting part on the top of the boiler
called the "steam chest," of which the purpose is to retain for the use of
the cylinder a certain supply of steam in a quiescent state, in order that
it may have time to clear itself of foam or spray. A steam chest is a usual
part of all marine boilers. In fig. 9 A is the furnace, B the steam chest,
and C the smoke box which opens into the chimney. The front of the smoke
box is usually closed by doors which may be opened when necessary to sweep
the soot out of the tubes.

The following are some forms of American boilers:

Figs. 12 and 13 are the transverse and longitudinal sections of a common
form of American marine boiler.

Figs. 14 and 15 are the front and sectional elevation of one of the boilers
of the U.S. steamer Water Witch.

[Illustration: Fig. 12.]

[Illustration: Fig. 13.]

[Illustration: Fig. 14.]

[Illustration: Fig. 15.]