. The Street railway journal . EXPRESS PLATFORM LOCAL PLATFORM. about 5 miles or per cent of the road; (5) cast-iron tubesused under the Harlem and East Rivers. The general character of the flat roof I-beam construction isshown in the view on page 471. The bottom is of con-crete. The side walls have I-beam columns 5 ft. apart, betweenwhich are vertical concrete arches, the steel acting as a sup-port for the masonry and allowing the thickness of the wallsto be materially reduced from that necessary were nothing butconcrete used. The tops of the wall columns are connected byroof beams which
. The Street railway journal . EXPRESS PLATFORM LOCAL PLATFORM. about 5 miles or per cent of the road; (5) cast-iron tubesused under the Harlem and East Rivers. The general character of the flat roof I-beam construction isshown in the view on page 471. The bottom is of con-crete. The side walls have I-beam columns 5 ft. apart, betweenwhich are vertical concrete arches, the steel acting as a sup-port for the masonry and allowing the thickness of the wallsto be materially reduced from that necessary were nothing butconcrete used. The tops of the wall columns are connected byroof beams which are supported by rows of steel columns be-tween the tracks, built on concrete and cut stone basis form-ing part of the floor system. Concrete arches between theroof beams complete the top of the subway. Such a structureis not impervious, and hence, there has been laid behind theside walls, under the floor and over the roof, a course of twoto eight thicknesses of felt, each washed with hot asphalt aslaid. In addition to this precaution against dampness, in th
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
