SUBWAYS. The system of engineering beneath the public streets has not by any means yet reached its full development. Subways for foot passengers are occasionally constructed in connection with railway termini : one such connects the Bishopsgate street station of the Metropolitan railway with the Liverpool street station of the Great Eastern; another connects two Victoria stations at Pimlico, belonging to different lines and com panies. The Tower Subway is a remarkable instance of a passage under the Thames for foot-passengers. The Metropolitan or underground railway, opened in 1863, was the first example of its kind; the passengers going down stairs from the side-pavements to stations underneath the carnage-way. The pneumatic propulsion of mail-bags (see PNEUMATIC DISPATCH) has given rise to projects for a similar mode of propelling rail way trains beneath streets and roads. One such, the Waterloo and Whitehall railway, was commenced about 1865, to pass under the Thames; want of funds led to its aban. donment after shafts had been sunk. The term subways is usually applied, not to such tunneled for traveling, but to roomy archways that will contain sewer-pipes, water-pipes, and gas-pipes. It has been long consided a defective system that whenever such pipes need repair, the surface of the street has to be broken up to get at them, thereby causing great expense and great interruption to traffic. When the metropolitan board of works commenced their series of improvements, they resolved on the trial of subways for this useful purpose. They began with a new street, extending from Covent Garden market to St. Martin's lane, opened in 1861. Underneath the carriage-way of this street, there is a subway, a central arched passage or tunnel 12 ft. wide by 6} ft. high; with arched side-openings for house service-pipes connected with the cellarage of the several dwellings. In this subway are water-pipes, gas-pipes, and electro-telegraphic wires, all easy of access by side entrances to the subway, of sufficient size to admit workmen, pipes, etc. In this instance, the main sewer is not in the subway itself, but underneath it, provided with man-holes, gullies, ventilating shafts, etc. A second ex ample is afforded by Southwark street, lately formed from Blackfriars road to the southern foot of London bridg6. Underneath this street extends a subway, excellently planned for the purposes above mentioned. Two street lamp-posts, of unusually elegant design, one at each end of the street, act as ventilating shafts for the subway, and there are other ventilators along the route, besides side entrances for workmen. A curious
proof has been furnished, however, of the anomalies which so frequently mar our pub lic works. In 1865, a gas company broke up the roadway, and broke through the well built crown of the arch of the subway, to get at their gas-pipes for purposes of repair or adjustment. It was found, on investigation, that no one had power to prevent them. The act empowered the metropolitan board of works to make a subway for the use of gas companies, water companies etc. ; the gas company, on the other hand, were em powered by their act to break up the public roadways to get at their pipes; the board could not compel the company to adopt the new plan, because the powers were only per missive, not obligatory. The water companies and gas companies fear incurring addi tional expense; and there is known to be a difference of opinion among engineers con cerning the danger from leakage and explosion when the two sets of pipes are inclosed in the same archway.
The subway system, after overcoming these and other difficulties, has made a great advance within a recent period. Queen Victoria street, and several other new streets, have been provided with subways similar to that under Southwark street. The Victoria or northern Thames embankment presents some fine examples of subway engineering. Between the masonry of the river-wall and the former line of high water, there are no less than three tunnels or arched passages under the surface of the ground parallel to the course of the river. One is the metropolitan district railway; another is the low-level sewer of the Great Main Drainage system; while a third is a subway to contain gas and water-pipes, telegraph wires, etc. The most extraordinary plan, perhaps, ever seriously proposed in subway engineering is connected with the spot where Tottenham Court road, Euston road, and Hampstead road join. The Metropolitan railway is here flanked on either side by sewers; above it, but below the level of the street, are several gas and water pipes, drains, and ventilating shafts; while crossing immediately over the Metro politan railway, at right angles, is the tube of the (still abortive, 1879) pneumatic dis patch (q.v.). Beneath all this is the section of another tunnel, intended to join the Mid land and North-western railways with the South-eastern. Civil engineers and contrac tors are ready to grapple with the difficulties of this extraordinary work whenever finan cial circumstances are favorable.