Subways. The term subway has been most generally applied to arched passages or small tunnels under streets for the purpose of containing gas-pipes, water-pipes, and sometimes sewer-pipes, or at least drains for surface-water. Some also contain telegraph-wires and pipes for the transmission of compressed air. They are made of sufficient size to permit of workmen walking to and fro in them to examine the pipes and to execute repairs. It need hardly be said that in large towns such subways are a great public benefit. They save the necessity for breaking up streets to get at the pipes for repairs, an operation which not only obstructs the traffic, but prevents the roadways and foot-pavements from being kept in proper condition. Paris has long had an extensive system of subways for the purposes above noted. These are built of stone, and are of various shapes, being circular, oval, or egg shaped, or with straight sides and semicircular top. The lower portions of them are stepped for footpaths, with a track for the drain between these. A number of these subways have been constructed in London—in Southwark Street, Queen Victoria Street, and the Thames Embankment, for example. The subway under the roadway of the Boulevard Sebastopol, one of the largest in Paris, is 16 feet wide and 11 feet high; that under the footway of the Thames Embankment is 9 feet wide and 7 feet 3 inches high.
Another class of subways which has been extensively constructed of late years both in Britain and abroad comprises arched passages under railways to enable passengers to pass from one side to another of a station, or to communicate between two adjacent railway stations. In some cases these are elaborate examples of underground engineering, and when they are faced with glazed bricks, as most of them are, they have a clean and elegant appearance.
The name subway was in general use during its construction for the deep tunnel electric railway between the City and Southwark, now called the City and South London Railway, which was opened in 1890. Two separate tunnels were made for this line—one for the up and another for the down traffic. At the stations the passengers descend and ascend by hydraulic lifts, unless they prefer to use the stairs. A second underground electric railway, the City and Waterloo, miles, was opened in 1898, and another from Waterloo to Baker Street was making in 1899. The obvious advantage of having so much of the local passenger traffic withdrawn from the crowded streets promises to develop this method of underground railways in London and other busy cities. See TUNNEL.
Consult the Proceedings of Civil Engineers, vol. xxiv., for the drains and subways of London and Paris; Les Promenades de Paris (1873), for sections of the Paris subways; and Engineering, vols. xlix. and 1. (1890), for papers on the City and Southwark subway.