The _Nadrai Aqueduct Bridge_, in India, opened at the end of 1889, is the largest structure of its kind in existence. It was built to carry the water of the Lower Ganges canal over the Kali Naddi, in connexion with the irrigation canals of the north-west provinces. In the year 1888-1889 this canal had 564 m. of main line, with 2050 m. of minor distributaries, and irrigated 519,022 acres of crops. The new bridge replaces one of much smaller size (five spans of 35 ft.), which was completely destroyed by a high flood in July 1885. It gives the river a waterway of 21,000 sq. ft., and the canal a waterway of 1040 sq. ft., the latter representing a discharge of 4100 cub. ft. per second. Its length is 1310 ft., and it is carried on fifteen arches having a span of 60 ft. The width between the faces of the arches is 149 ft. The foundations below the river-bed have a depth of 52 ft., and the total height of the structure is 88 ft. It cost 44½ lakhs of rupees, and occupied four years in building. The foundations consist of 268 circular brick cylinders, and the fifteen spans are arranged in three groups, divided by abutment piers; the latter are founded on a double row of 12-ft. cylinders, and the intermediate piers on a single row of 20-ft. cylinders, all the cylinders being hearted with hydraulic lime concrete filled in with skips. This aqueduct-bridge has a very fine appearance, owing to its massive proportions and design. (E. P. H.*)
AUTHORITIES.--For ancient aqueducts in general: Curt Merckel, _Die Ingenieurtechnik im Alterthum_ (Berlin, 1899); ch. vi. contains a very full account from the earliest Assyrian aqueducts onwards, with illustrations, measurements and an excellent bibliography. For Greek aqueducts see E. Curtius, "Über städtische Wasserbauten der Hellenen," in _Archaeologische Zeitung_ (1847); G. Weber (as above); papers in _Athen. Mittheil._ (Samos), 1877, (Enneacrunus) 1892, 1893, 1894, 1905, and articles on ATHENS, PERGAMUM, &c. For Roman aqueducts: R. Lanciani, "I Commentari di Frontino intorno le acque e gli acquedotti," in _Memorie dei Lincei_, serie iii. vol. iv. (Rome, 1880), 215 sqq., and separately; C. Herschel, _The Two Books on the Water Supply of the City of Rome of Sextus Julius Frontinus_ (Boston, 1899); T. Ashby in _Classical Review_ (1902), 336, and articles in _The Builder_; cf. also the maps to T. Ashby's "Classical Topography of the Roman Campagna," in _Papers of the British School at Rome_, i., in., iv. (in progress).