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The New York Subway - Its Construction and Equipment by Anonymous
page 43 of 199 (21%)
are the systems of terra-cotta ducts in which the electric cables are
placed. The cables can be reached by means of manholes every 200 to
450 feet, which open into the subway and also into the street. The
number of these ducts ranges from 128 down to 32, and they are
connected with the main power station at 58th and 59th Streets and the
Hudson River by a 128-duct subway under the former street.

[Sidenote: _Reinforced
Concrete
Construction_]

The reinforced concrete construction substitutes for the steel roof
beams, steel rods, approximating 1-1/4 inches square, laid in varying
distances according to the different roof loads, from six to ten
inches apart. Rods 1-1/8 inches in diameter tie the side walls,
passing through angle columns in the walls and the bulb-angle columns
in the center. Layers of concrete are laid over the roof rods to a
thickness of from eighteen to thirty inches, and carried two inches
below the rods, imbedding them. For the sides similar square rods and
concrete are used and angle columns five feet apart. The concrete of
the side walls is from fifteen to eighteen inches thick. This type is
shown by photographs on page 41. The rods used are of both square
and twisted form.

[Illustration: LAYING SHEET WATERPROOFING IN BOTTOM]

[Illustration: SPECIAL BRICK AND ASPHALT WATERPROOFING]

[Sidenote: _Methods of
Construction
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