s of the downtakes are
of cast iron, except the vertical parts in front of the boilers, which
are of wrought-iron pipe. These vertical downtakes are 10 inches in
inside diameter, while all others are 14 inches in inside diameter.

[Sidenote: _Main Boiler
Room_]

The main boiler room is designed to receive ultimately seventy-two
safety water tube three drum boilers, each having 6,008 square feet of
effective heating surface, by which the aggregate heating surface of
the boiler room will be 432,576 square feet.

There are fifty-two boilers erected in pairs, or batteries, and
between each battery is a passageway five feet wide. The boilers are
designed for a working steam pressure of 225 pounds per square inch
and for a hydraulic test pressure of 300 pounds per square inch. Each
boiler is provided with twenty-one vertical water tube sections, and
each section is fourteen tubes high. The tubes are of lap welded,
charcoal iron, 4 inches in diameter and 18 feet long. The drums are 42
inches in diameter and 23 feet and 10 inches long. All parts are of
open-hearth steel; the shell plates are 9/16 of an inch thick and the
drum head plates 11/16 inch, and in this respect the thickness of
material employed is slightly in excess of standard practice. Another
advance on standard practice is in the riveting of the circular seams,
these being lap-jointed and double riveted. All longitudinal seams are
butt-strapped, inside and outside, and secured by six rows of rivets.
Manholes are only provided for the front heads, and each front head is
provided with a special heavy bronze pad, for making connection to the
stop and check feed water valve.

[Illustration: OPERATING ROOM SHOWING CONDENSERS--POWER HOUSE]

The setting of the boiler embodies several special features which are
new in boiler erection. The boilers are set higher up from the floor
than in standard practice, the center of the drums being 19 feet above
the floor line. This feature provides a higher combustion chamber, for
either hand-fired grates or automatic stokers; and for inclined grate
stokers the fire is carried well up above the supporting girders under
the side walls, so that these girders will not be heated by proximity
to the fire.

As regards the masonry setting, practically the entire inside surface
exposed to the hot gases is lined with a high grade of fire brick. The
back of the setting, where the rear cleaning is done, is provided with
a sliding floor pl