Aq´ueduct

(Lat. aqua , water, duco , to lead), an artificial channel or conduit for the conveyance of water from one place to another: more particularly applied to structures for conveying water from distant sources for the supply of large cities. Aqueducts were extensively used by the Romans, and many of them still remain in different places on the Continent of Europe, some being still in use. The Pont du Gard in the south of France, 14 miles from Nîmes, is still nearly perfect, and is a grand monument of the Roman occupation of this country. The ancient aqueducts were constructed of stone or brick, sometimes tunnelled through hills, and carried over valleys and rivers on arches. The Pont du Gard spans the River Gard, and was built to convey to Nîmes the water of springs rising in the neighbourhood of the modern Uzés. It is built of great blocks of stone; its height is 160 feet; length of the highest arcade, 882 feet. The aqueduct at Segovia, originally built by the Romans, has in some parts two tiers of arcades 100 feet high, is 2921 feet in length, and is one of the most admired works of antiquity. One of the most remarkable aqueducts of modern times is that constructed by Louis XIV for conveying the waters of the Eure to Versailles. The extensive application of metal pipes has rendered the construction of aqueducts of the old type le nece ary; but what may be called aqueduct bridges are still frequently constructed in connection with canals and also with water-works for the supply of towns. Where canals exist canal aqueducts are common, since the water in any section of a canal must be kept on a perfect level. IMG:4014330425200354480_image081.jpg:Aqueduct Aqueduct at Segovia Many large towns now derive a supply of water from sources at a great distance, and in 210 bringing the water to the place where it is required much tunnelling is often nece ary as well as digging and excavating in the open. A tunnel furnishing a water channel may be driven through miles of rock strata of various kinds, and in many places it may have to be lined with concrete or cement wholly or partially, brick-work also being much employed. Instead of tunnelling, the channel may be formed on the plan of 'cut and cover', being first cut in the ground and then covered over, leaving the surface much in the same state as before. And, of course, iron piping is often used in connection with such tunnels, the water being conveyed so far in an aqueduct of one kind, and so far in one of another kind, according as is deemed most suitable. In the Thirl mere aqueduct, which brings water to Manchester, there are 45 miles of cast-iron pipes, 37 miles of cut-and-cover work, and 14 miles of tunnels proper. Pipes are naturally laid where valleys occur, and the water simply enters the pipes at one end and flows out at the other by the influence of gravity, there being a suitable chamber constructed at either end of the pipe line where there is a junction with a section of tunnel. Aqueduct bridges were first introduced into England in the eighteenth century, the first being the aqueduct at Barton Bridge conveying the Bridge water Canal acro the Irwell. In such bridges the water-channel may be made of cast iron. There are great aqueduct bridges on some of the Indian canals, such as the Nadrai bridge on the Lower Ganges Canal. In America water is often carried long distances in flumes or open wooden channels, supported, where nece ary, on trestles. Great wooden pipes are also common there, built of large staves and hooped round with iron or steel. These often rest on the surface of the ground without any covering.— Bibliography : C. Herschel, Front in us ; Wegmann, Water-supply of City of New York ; J. F. Bateman, The Manchester Waterworks ; J. M. Gale, The Glasgow Waterworks ; A. Pre scott Folwell, Water Supply Engineering .