Engineering Wonders of the World
Volume III

180 ENGINEERING WONDERS OF THE WORLD. was laid in the first instance—and one line of 36-inch pipes. This aqueduct, which passes 40,000,000 gallons a day, was commenced in 1855, and opened in 1859. Its ruling gradient is 10 inches in the mile. The Glasgow water supply was increased subsequently by a new aqueduct, which fol- lows much the same course as the old, but has a daily capacity greater by about 20,000,000 gallons. A more ambitious scheme than that de- scribed thus briefly was one set on foot in the late ’seventies by the Corporation of Liverpool for supplying that great city The Vyrnwy- with water from either the Lake District of Cumberland or from the valleys of North Wales. It was decided to impound the Vyrnwy, a tributary of the Severn, in Rad or- shire, by means of a masonry dam, and conduct the waters of the reservoir so formed through an aqueduct 68J miles long to reservoirs at Prescot, 8 j miles east of the Liverpool Town Hall. During 1879 the late Mr. G. F. Deacon, M.Inst.C.E., the engineer in charge of the works, completed the surveys and prepared the Parliamentary plans. In 1880 the Act conferring the necessary powers received the Royal Assent, and in the follow- ing year operations commenced. A site for the great masonry dam im- pounding Lake Vyrnwy, which at high-water level contains more than 12,000,000,000 gal- lons, was selected at the crest The Vyrnwy Qf a nafural jam formed across Dam. the bed of the valley by glacial action at some far distant period. The dam is 1,172 feet long at the crest, 161 feet high above the lowest point in the founda- tions, and 127 feet thick (maximum) at the base. It contains 260,000 cubic yards of masonry, and weighs 679,000 tons. Across the top runs a fine carriage-way on arches, through nineteen of which passes all surplus SKETCH MAP SHOWING THE COURSE OF THE LIVERPOOL AQUEDUCT. Tunnels are indicated by broken lines. water in times of heavy rain, and falls in an almost unbroken sheet down the face of the dam into the valley below. To ensure a secure foundation the bed had to be trenched to firm rock, and during this process huge masses of rock, weighing in some cases hundreds of tons, were blasted and removed. The interior rubble work and the facings of rectangular stones were built up with the greatest possible care round large discharge culverts. At each end th© masonry is tied into the native rock.