Engineering Wonders of the World
Volume III

STEEL ARCH OF 150 FEET SPAN CARRYING THE PIPES OF ’THE ELAN-BIRMINGHAM AQUEDUCT ACROSS THE SEVERN. (Photo, by courtesy of Messrs. J. Mansergh and Sons.) GREAT BRITISH DAMS AND AQUEDUCTS. BY THE EDITOR. THE concentration of human beings into densely-populated areas, the conse- quent fouling of local surface water supplies, and the exhaustion or insufficiency of deep wells, give rise to the very serious problem of how to supply huge cities with a Roman Aqueducts. copious supply of wholesome water. The Romans faced the problem many centuries ago, and solved it by leading water from dis- tant and unpolluted sources through masonry ducts, the remains of which are sufficient proof of the genius of the constructors. Roman engineers had so to plan and build their (1,408) aqueducts that the surface of the water should follow the hydraulic gradient—an imaginary line joining the point of entry of the supply and the point of its ultimate discharge. Their aqueducts were, in fact, artificial rivers, which had to be carried on arches or walls across valleys and places where the natural surface of the ground fell below the hydraulic gradient. In order to avoid tunnelling—a v.ery difficult matter to the ancients—hills had to be skirted, the length of the aqueduct increased, and the gradient flattened, which in turn involved the enlargement of the cross sectional area of the channel. VOL. in.