s of The Babcock &
Wilcox, Ltd., with No. 18 proved that proper attention to details of
construction would make it a most desirable form of boiler where
headroom was limited. A large number of this design have been
successfully installed and are giving satisfactory results under widely
varying conditions. The cross drum boiler is also built in a vertical
header design.

Boilers Nos. 21, 22 and 23, with a few modifications, are now the
standard forms. These designs are illustrated, as they are constructed
to-day, on pages 48, 52, 54, 58 and 60.

The last step in the development of the water-tube boiler, beyond which
it seems almost impossible for science and skill to advance, consists in
the making of all pressure parts of the boiler of wrought steel,
including sinuous headers, cross boxes, nozzles, and the like. This
construction was the result of the demands of certain Continental laws
that are coming into general vogue in this country. The Babcock & Wilcox
Co. have at the present time a plant producing steel forgings that have
been pronounced by the _London Engineer_ to be "a perfect triumph
of the forgers' art".

The various designs of this all wrought-steel boiler are fully
illustrated in the following pages.

[Illustration: Wrought-steel Vertical Header Longitudinal Drum Babcock &
Wilcox Boiler, Equipped with Babcock & Wilcox Superheater and Babcock &
Wilcox Chain Grate Stoker]

THE BABCOCK & WILCOX BOILER

The following brief description of the Babcock & Wilcox boiler will
clearly indicate the manner in which it fulfills the requirements of the
perfect steam boiler already enumerated.

The Babcock & Wilcox boiler is built in two general classes, the
longitudinal drum type and the cross drum type. Either of these designs
may be constructed with vertical or inclined headers, and the headers in
turn may be of wrought steel or cast iron dependent upon the working
pressure for which the boiler is constructed. The headers may be of
different lengths, that is, may connect different numbers of tubes, and
it is by a change in the number of tubes in height per section and the
number of sections in width that the size of the boiler is varied.

The longitudinal drum boiler is the generally accepted standard of
Babcock & Wilcox construction. The cross drum boiler, though originally
designed to meet certain conditions of headroom, has become popular for
numerous classes of work where low headroom is not a requ