Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/245

Rh AQUEDUCT 227 length, and upwards of 500 feet below the summit of tlie Lill^ and the Mugdock Tunnel at the eud of the aqueduct, 2640 yards in length, there are &quot; others, 700, 800, 1100, and 1400 yards in length. Not to speak of smaller con structions, there are twenty-five important iron and masonry aqueducts over rivers and ravines, some 60 and 80 feet in height, with arches of 30 feet, 50 feet, and 90 feet in span. The number of people employed, exclusive of iron-founders / LOCH KATRINE / 2325Zar&amp;lt;?s ^-2O^|^32 1^~ |p /IQUEDUC FALL /O r a fT //VC//S /Af / &amp;gt;AMETf: MILE

Fia. 19. Part Section of Loch Katrine Aqueduct. and mechanics, has generally been about 3000 j and for the greater part of these, huts and roads and all other accommodation had to be provided, the country for the most part being of the wildest and most inaccessible description.&quot; &quot;At the picturesque, turf and timber village of Sebastopol, as the miners called it, at the head of Loch Chon, several hundreds of work-people were accommodated. Provision stores, reading-rooms, a school- house and church, and a resident medical man and school master were provided for them.&quot; The aqueduct from its commencement at Loch Katrine to the Mugdock reservoir, is 25| miles long, 13 of which were tunnelled, 3| miles are iron piping across valleys, and the remaining 9 miles consist of &quot; cut and cover &quot; conduit and bridges. Where the ground was cut open the conduit was covered in, and the surface restored after the aqueduct was built. At the bridges the aqueduct is covered with timber to prevent its being choked by snow. Most of them are furnished with grooves in the masonry to receive stop planks, and with discharge sluices to facilitate the emptying of the aqueduct, when it is necessary to inspect or make repairs. Overflows are constructed at a number of the bridges, to discharge the water if it should be necessary to stop the flow suddenly at any point. The total cost of the aqueduct at the time the water was introduced into the city, was .468,000, or an average of 18,000 per mile. It has been already stated that the 4-feet pipes across the valleys on the line of aqueduct were intended to deliver 20,000,000 gallons a day. By the well-known modification of Eytelwein s formula, deduced from Du Buat s experiments and more elaborate formulae, the com puted discharge is 21,500,000 gallons a day nearly, and by Weisbach s formulae, 21,750,OUO gallons a day. These pipes, however, have discharged 24,000,000 gallons a day without their being completely gorged, and their ultimate discharge has therefore yet to be determined. The whole of the pipes used in the works were coated with coal pitch and. oil, according to the process patented by Dr E. A. Smith of Manchester, and first used by Mr Bateman in the Manchester Waterworks. This coating, when well done, imparts a smooth glassy surface to the pipes, and prevents, at least for a number of years, the usual, and it may be said, inevitable oxidation. Weisbach found that for wooden pipes 2 1 and 4| inches diameter, the coefficient of resist ance was 1 75 times as great as for &quot;metallic pipes,&quot; giving a discharge about 14 per cent, less; and M. Morin Las shown, in a paper which it is believed is published in detail in the Memoires des Savants Etrangers, the influence the state of the surface Las upon the discharge of a pipe, amounting, in cast-iron pipes coated with pitch, and in glass pipes, to an increase of nearly one-third in the discharge. It has also been pointed out by M. Morin, whose deduc tions are principally from observations by M. Darcy director of the waterworks of Paris, that for large sizes the diameters of the pipes seem also to exercise a more decided influence on the discharge than has been hitherto assigned to them. Late observations on the flow of gas through pipes by M. Arson, engineer of the Paris Gas Company, tend to confirm the views of M. Morin. At the Mugdock Service Beservoir, 7 or 8 miles from Glasgow, the water is first discharged into a basin, from which it passes over cast-iron gauge plates, 40 feet wide, brought to a thin edge. The depth of water passing over these plates is regularly recorded and the discharge com puted. From the basin the water falls into an upper division of the main reservoir, about 2 acres in extent, and from this it is discharged into the reservoir. The reser voir has a water surface of 60 acres, and a depth when full of 50 feet ; it contains 548,000,000 gallons, and is 317 feet above ordnance datum. It admits of repairs being made upon the aqueduct without interrupting the supply of water to the city. Two earthen embankments were necessary to form the reservoir ; the main embankment is 400 yards long and 68 feet high, and the easterly embankment 240 yards long and 50 feet high, each with a puddle wall in the centre, and pitching on the front slope in the usual way. The water is drawn from the reservoir by pipes laid in a tunnel through the hill between the two embankments, there being no pipes through the embankments themselves. At the end next the reservoir there is a stand-pipe so arranged that water can be drawn at various heights, and about 50 yards from the reservoir, the water passes into a circular well cut out of the rock, 40 feet in diameter and 63 feet deep, and is strained by passing through copper wire-cloth, 40 meshes to the inch, arranged in oak frames, forming an inner well of octagonal shape 25 feet diameter ; and from this latter the water finally passes into the two lines of pipes leading to the city. Water can also be drawn direct from the gauge basin, and from the upper compartment of the reservoir into the straining well, by a line of 4-feet pipes through the bottom of the reservoir. These works, including road and stream diversions, cost about 56,000. The two pipes leading from the straining well are each 42 inches diameter, and are intended to deliver the whole 50,000,000 gallons a day; but on emerging from the tunnel, which is 440 yards in length, they are diminished to 36 inches, and they are continued of this size to the city. Provision was made for additional pipes, which have since been laid. The different lines of pipes are laid side by side for about 3 miles, after which they diverge one line being carried by the Great Western Road for the supply of the low districts of the city, and the other by Maryhill for the supply of the high districts. These pipes come together again, and are arranged so as to communicate when necessary at St George s Boad near the commencement of the city, up to which point their respective lengths from the straining well are 7 miles for the low district main, and 6 miles for the high. Each of these lines of pipes crosses the River Kelvin and the Forth and Clyde Canal, and at these places provision was made for additional pipes. Eleven feet were added to the width of the Kelvin Bridge on the Great Western Boad, by cast-iron girders, to carry the low district mains. The two middle spans are each 93 feet, and the two side arches 37 feet span. The total cost of the works at their completion, in 15 GO, was as follows :