The New York Rapid-transit Subway

Proceedings.] PARSONS ON NEW YORK RAPID-TRANSIT SUBWAY. 39 was connected with two or more pipes of a suitable size to aggregate the proper area. In all instances but one it was found possible to pass sewers under the subway without siphoning, by carrying the sewer on tlie down-stream side at a lower level, and with a continuous but less fall, until the new gradient met the old. In the case in question the subway-bottom was beneath tide-level and cut off a large drainage-area. The circular sewer had a diameter of G feet. On the upper side of the subway a large chamber 10 feet across was constructed. At the upper end of this chamber there was a sludge-well 6 feet by 10 feet in plan, divided longitudinally by a brick wall, witli grooves at the upper end so arranged that by means of stop-planks either part of the sludge-well could be cut off. Across the lower end of this chamber there was a dam, in front of which was a 14-inch cast-iron pipe whose capacity was sufficient to take the entire dry-weather flow of the sewer. When the sewage-flow exceeded the capacity of the 14-inch pipe, it flowed over the dam into the second part of the chamber, from which there led two 42-inch cast-iron pipes. These two pipes, together with the 14-inch pipe, were embedded in a mass of concrete and carried beneath the subway to a second chamber on the down-stream side into which the pipes discharge, but through separate passages. The 14-inch pipe was always left open at the down-stream end for continuous flow. At the discharge.- mouths of the large pipes grooves were again made for stop-planks. Normally both the 42-inch pipes are dry, and by introducing stop- planks at the lower end they can be examined at any time and cleaned of any deposit. The continuous flow through the small pipe keeps that clear. The arrangement of this siphon has been found by experience to work well. Materials. The two materials used in greatest quantity in the subway were iron, either as steel or cast iron, and.cement. For the inspection of these materials a fully-equipped inspection-bureau was established, and all the material, cement as well as metal, was inspected at the mills and not upon the ground after delivery. The steel was required to show a tensile strength of not less than 58,000 lbs., and not more than 68,000 lbs., per square inch, with an elastic limit of 35,000 lbs. per square inch, an elongation of 20 pel- cent. in 8 inches and reduction of area at the point of fracture by 44 per cent.; in addition the steel was subjected to certain physical