girders and longitudinal rolled beams, arranged to suit the particular
requirements of the imposed loads of the boilers, economizers, coal,
etc., while the engine-room floors and pipe and switchboard galleries
are in general framed with longitudinal plate girders and transverse
beams.

There are seven coal bunkers in the boiler house, of which five are 77
feet and two 41 feet in length by 60 feet in width at the top, the
combined maximum capacity being 18,000 tons. The bunkers are separated
from each other by the six chimneys spaced along the center line of
the boiler house. The bottom of the bunkers are at the fifth floor, at
an elevation of about 66 feet above the basement. The bunkers are
constructed with double, transverse, plate girder frames at each line
of columns, combined with struts and ties, which balance the outward
thrust of the coal against the sides. The frames form the outline of
the bunkers with slides sloping at 45 degrees, and carry longitudinal
I-beams, between which are built concrete arches, reinforced with
expanded metal, the whole surface being filled with concrete over the
tops of the beams and given a two-inch granolithic finish.

[Illustration: 58TH ST. POWER HOUSE--GENERAL PLAN OF COAL BUNKERS AND
ECONOMIZERS.]

[Illustration: 58TH ST. POWER HOUSE--GENERAL PLAN OF MAIN OPERATING
FLOOR.]

The six chimneys, spaced 108 feet apart, and occupying the space
between the ends of the adjacent coal bunkers, are supported on
plate-girder platforms in the fifth floor, leaving the space below
clear for a symmetrical arrangement of the boilers and economizers