mps, which close the openings from the inside and which are secured
by ball-headed bolts to assure proper alignment. All joints are made
tight, metal to metal, without packing of any kind.

The mud drum to which the sections are attached at the lower end of the
rear headers, is a forged-steel box 7-1/4 inches square, and of such
length as to be connected to all headers by means of wrought nipples
expanded into counterbored seats. The mud drum is furnished with handholes
for cleaning, these being closed from the inside by forged-steel plates
with studs, and secured on a faced seat in the mud drum by forged-steel
binders and nuts. The joints between the plates and the drum are made
with thin gaskets. The mud drum is tapped for blow-off connection.

All connections between drums and sections and between sections and mud
drum are of hot finished seamless open-hearth steel tubes of No. 9
B. W. G.

Boilers of the longitudinal drum type are suspended front and rear from
wrought-steel supporting frames entirely independent of the brickwork.
This allows for expansion and contraction of the pressure parts without
straining either the boiler or the brickwork, and also allows of
brickwork repair or renewal without in any way disturbing the boiler or
its connections.

[Illustration: Babcock & Wilcox Wrought-steel Vertical Header Cross Drum
Boiler]

CROSS DRUM CONSTRUCTION--The cross drum type of boilers differs from the
longitudinal only in drum construction and method of support. The drum
in this type is placed transversely across the rear of the boiler and is
connected to the sections by means of circulating tubes expanded into
bored seats.

The drums for all pressures are of two sheets of sufficient thickness to
give the required factor of safety. The longitudinal seams are double
riveted butt strapped, the straps being bent to the proper radius in an
hydraulic press. The circulating tubes are expanded into the drums at
the seams, the butt straps serving as tube seats.

The drumheads, drum fittings and features of riveting are the same in
the cross drum as in the longitudinal types. The sections and mud drum
are also the same for the two types.

Cross drum boilers are supported at the rear on the mud drum which rests
on cast-iron foundation plates. They are suspended at the front from a
wrought-iron supporting frame, each section being suspended
independently from the cross members by hook suspension bolts. This
method