The New York Rapid-transit Subway

130 CORRESPONDENCE ON NEW YORK SUBWAY. [Minutas of Dr. Soper, arrangements for ventilation were, therefore, on the whole, abundant. To have installed fans or blowers would have been a useless waste of money. In order to improve local conditions it was only necessary to remove some of the vault-lights overhead. This could be done easily and quickly. Subways of this type breathed of themselves when given a cliance. The removal of heat from a subway was an interesting problem. It was evident that the heat must pass through the walls and so be carried away by the surrounding material, or it must escape with the air. So long as a subway structure was surrounded by wet or moist material the conduction of heat through the walls might be considerable. With all subways it was so when the road was new ; hence overheating did not occur at first. Most subways, however, gradually became warm with age, and it appeared that this rise in temperature was due to saturation of the structure and its surroundings by the heat which could not escape. Apparently there was only one way to prevent discomfort from heat in a deep subway, and that was by consuming less power. This was equivalent to saying that fewer trains must be run, they must be lighter, or they must be run at a lower speed. The Mr. Tait. economizing of power by regenerative control seemed not to offer sufficient advantages at the present time for extensive use in subways. In a subway of the type constructed by the Author, another method of keeping down the temperature was available. By providing very large openings to the outside air a substantial amount of relief could be afforded through ventilation. The quantity of air which could be moved in and out of a shallow subway under properly arranged conditions was enormous. The most important sanitary requirement in connection with subways was that they should be kept clean. He was not aware of any important subway in America or Europe that was maintained in such a way as to indicate that this necessity was fully appreciated. Mr. W. A. Tait, having seen the work during construction, was greatly impressed with the enterprise that had been shown. At the same time, the ground passed through, in and near the busy parts of New York, seemed to be infinitely better, from a constructional point of view, than a great deal of the ground through which the Glasgow Central railway passed.1 Regard must also be had to the facilities granted to and freely taken advantage of by the contractors for the temporary diversion of water- and other mains by means of trestles along the footpath. He did not recollect having ever seen similar facilities granted during the carrying out of underground railway- 1 Minutes of Proceedings Inst. C.E., vol, exxiii, p. 120.