SUBWAYS (FOR PIPES AND WIRES ) . Under ground galleries which contain and render ac cessible at any point the multitudinous pipes and wires beneath city pavements; or else duets for inclosing underground wires only, in such a way as to make them accessible at intervals. Subterranean passages for the accommodation of street traffic are either nothing more than streets or footpaths placed in tunnels, which need no description, or they are underground rail ways, which are described in the article on TtiNx EL.
The chief advantages of subways for pipes and wires are: (1) They increase the life and general tingliam, England. Subsequently a number of subways were added to the first ones built in London and Nottingham. The London subways range in size from 14 feet wide and 7 feet high to 8X7 feet. The walls are of brick, laid in cement. The roofs are formed by semicireular brick arches, with ventilators extending to the streets at intervals of 100 feet. The London subways contain gas, water, electric light, hy draulic power supply, telephone, and telegraph mains. The placing of wires and a great variety of pipes in the sewers of Paris is one of the no table features of that city.
In the United States the nearest approach to subways like those of Europe is at Saint Paul, where a number of miles of sewers have been constructed in the form of tunnels in the soft sand-rock which underlies the city, and water mains have also been placed, separately, in simi lar tunnels. Branch tunnels connect with the houses, in the same general way as branches serviceability of pavements and prevent the in terruption to traffic caused by street excava tions to gain access to pipes when simply buried in the ground. (2) They facilitate both the in
spection and repair of all classes of underground furniture, and thus lessen the number of trouble some and dangerous leaks from water and gas mains; they also aid in the prevention of elec trolysis, or the electrical decomposition of iron and lead conduits through stray electrical cur rents from overhead trolley systems. (3) Ven tilated and relatively dry subways may greatly lengthen the life of pipes and wires through better protection against corrosion than is pos sible when such furniture is laid directly in the earth.
One of the earliest attempts to avoid the dis turbance of pavements was carried out in Liver pool, where a gallery 21/2 feet wide was built under the sidewalk and in it were placed an oval pipe sewer 27X18 inches, a 10-inch water main, and a 10-inch gas main. The bottom of the trench was 13 feet below the surface of the sidewalk. Little or no provision for repairs was made. The London subways date from ]SGl or 1862, when one was built in a new street from Covent Carden Market to Saint Martin's Lane. A few months later a subway was built at Not lead to the buildings along the line of the Euro pean subways. Besides the sewers and water mains at Saint Paul some private companies have placed telephone lines in like tunnels. Tun nels for telephone cables have been constructed in Chicago.