R 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
from end to end of the building. The platforms are framed of
single-web girders 8 feet deep, thoroughly braced and carrying on
their top flanges a grillage of 20-inch I-beam. A system of bracing
for both the chimney platforms and coal bunkers is carried down to the
foundations in traverse planes about 30 feet apart.

The sixth tier of beams constitute a flat roof over a portion of the
building at the center and sides. In the engine room, at this level,
which is 64 feet above the engine-room floor, are provided the two
longitudinal lines of crane runway girders upon which are operated the
engine-room cranes. Runways for 10-ton hand cranes are also provided
for the full length of the boiler room, and for nearly the full length
of the north panel in the engine room.

Some of the loads carried by the steel structure are as follows: In
the engine house, operating on the longitudinal runways as mentioned,
are one 60-ton and one 25-ton electric traveling crane of 75 feet
span. The imposed loads of the steam-pipe galleries on the south side
and the switchboard galleries on the north side are somewhat
irregularly distributed, but are equivalent to uniform loads of 250 to
400 pounds per square foot. In the boiler house the weight of coal
carried is about 45 tons per longitudinal foot of the building; the
weight of the brick chimneys is 1,200 tons each; economizers, with
brick setting, about 4-1/2 tons per longitudinal foot; suspended
weight of the boilers 96 tons each, and the weight of the boiler
setting, carried on the first floor framing, 160 tons each. The weight
of structural steel used in the completed building is about 11,000
tons.

[Sidenote: _Power House
Superstructure_]

The design of the facework of the power house received the personal
attention of the directors of the company, and its character and the
class of materials to be employed were carefully considered. The
influence of the design on the future value of the property and the
condition of the environment in general were studied, together with
the factors relati