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Rh 224 AQUEDUCT gallons per day, caused great anxiety, and shewed the necessity of largely extended works. It was estimated that the basin above the Croton Dam, 339 square miles in area, would give 300,000,000 gallons per day on the average, if the water could be impounded, and that, therefore, abundant water could be obtained by increasing the number or capacity of the impounding reser voirs. New reservoirs were therefore projected, one of which, to contain 3,000,000,000 gallons, was expected to be completed in the autumn of 1872. With this the gross storage would be 4,670,000,000 gallons, in addition to the daily produce of the Croton River, which, at its minimum as stated, is 27,000,000 gallons per day. Another reservoir to contain 3,700,000,000 gal- FIG. 4. Cross sec tion of bridge. Ions was also projected, and will, it is presumed, be con structed when necessary (fig. 5). To meet the growing de- Diatribu tiny Reservoir -ft Union Square University Fid. 5. Part section of Croton Waterworks. mand for water, the reservoirs were not only increased as described, but the means of distribution were largely ex tended, and in one part of the city six lines of pipes 4 feet in diameter were laid side by side. Manchester Waterworks. The works by which the city of Manchester and its suburbs are now supplied with water, and which have been in course of construction from the year 1848 to the present time (1874), are perhaps, in some respects, the most stupendous works of the kind which have ever been constructed, in which difficulties of no ordinary char acter have been successfully overcome. These remarks, however, relate especially to the impounding reservoirs, which are seven in number, with embankments varying from 70 to 100 feet above the level of the valley in which they are constructed, and cannot, therefore, be properly alluded to here. As the conveyance of the water to the city is, however, by aqueduct, a few words explanatory of the general scheme will be necessary. The water is collected from the river Etherow and its tri butaries, which, rising on the westerly slope of the Pennine chain of hills, flow into the river Mersey, and so into the Irish Sea. The drainage ground from which the water is collected lies nearly midway between Manchester and Sheffield. Its area is about 19,300 acres. It rises in parts to an elevation of about 1800 feet above the level of the sea, and about 1200 or 1300 feet above the deep and romantic valley of Longdendale, in which the main collecting reservoirs are situated. The district consists of the shales and sandstones which constitute the lower portion of the Coal Measure formation the upper millstone grit forming the cap of the steep escarpments on each side of the valley, while the lower millstone grit, which may be said to separate the Coal Measure shale from the limestone shale, is found in the bottom. The waters produced by this geological forma tion are among the purest in the world. The spring water is especially brilliant, highly aerated, containing little or no foreign matter, and extremely soft. It is at all times very abundant, the district yielding much more spring water than the usual quantity, in proportion to the area from which the springs issue. The quantity of water flowing from the drainage ground would, if wholly stored, afford a gross supply of about 40,000,000 gallons per day, of which about 13,000,000 gallons per day have to be delivered as compensation to the mills on the stream, leaving about 27,000,000 gallons per day as the supply available for the city and its suburbs. The water of heavy rains and wet seasons is collected in large impounding reservoirs, the gross capacity of which is 4,233,000,000 gallons. In some of these reservoirs the turbid and coloured water is impounded, where it is allowed to settle and purify, and is subsequently given as compen sation to the stream ; and in others, the pure water, when more than sufficient for the wants of the city, is collected. Here it is stored till required, and then given in addition to the spring water, when that is in itself deficient in quantity. The spring water is separately collected, and conveyed to the city by aqueducts specially constructed for the purpose. In heavy rains, which swell the streams, and especially in autumn, the water is discoloured, but by a simple and ingenious contrivance, every stream is made to separate its coloured water from its pure water the coloured water being passed to reservoirs set apart for the storage of such water, and the pure water being sent at once to Manchester, or passed to reservoirs in which it is stored for future use. The aqueducts by which this water is conveyed from the springs and from the reservoirs, consist for the most part of tunnel and covered conduit, 6 feet in diameter, with a fall of 5 feet in a mile, with cast-iron syphon pipes of large dimensions across one valley, which has to be passed before the highest service reservoir is reached. From this reservoir to the city, about 8 miles distant, cast-iron pipes are laid along or under the public roads, to convey the water to various other reservoirs at lower elevations, from which the city and its suburbs are conveniently supplied. . In the main valleys in which the spring water is col lected, or the flood and turbid waters conveyed by separate channels, the aqueducts are chiefly open, and are, to a great extent, formed of concrete 6 inches thick on the sides and bottom, faced with dry stone pitching 9 inches in thickness. They are cheap, easily constructed, and per fectly successful. The area and capacities of all the reservoirs are as follows : Name. Area. Capacity. Depth. Woodhead, Acres. 135 Gallons. 1,235,000,000 feet. 72*; Torside, 160 1,474,000,000 84 Rhodes Wood, 54 500,000,000 68 Vale House, 63 343,000,000 40 Bottoms, (estimated) Arnfield, 46 39 399,000,000 209,000,000 50 52 Hollingworth, 13 73,000,000 52 Godley, 15 61,000,000 21 Denton, No. 1, 7 30,000,000 20 Denton, No. 2, 6 23,000,000 20 Gorton, Upper,,. 34 123,000,000 26 Gorton, Lower, 23 100,000 000 29 Prestwich, 4i 20,000 000 22 599 4,590,000,000 Lock Katrine Aqueduct, Glasgow. The Loch Katrine Aqueduct of the Glasgow Waterworks is the modern aqueduct which has most probably attracted the largest share of public attention.