Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/243

Rh AQUEDUCT 225 The appropriation of the beautiful waters of Loch Kat rine rendered classical by Sir Walter Scott the romantic, rugged, and almost impassable Highland country through which the aqueduct had to be constructed, and the distance from Loch Katrine to Glasgow, all contributed to lend a special interest to the undertaking. It is, however, a very simple work in itself, for, with but little artificial addition, Loch Katrine, Loch Venachar, and Loch Drunkie were converted into impounding reservoirs, the first for the supply of the city, and the two latter for compensation. The area and capacity of these reservoirs are as follows iminer Level. Extent to which I.oehs can lie Si X t&amp;gt; Capacity nge Area. 2. ~&quot; a &quot;c o&amp;lt; S rs raised or lowered c z. i 5 * 3 Q C.S C CJ &amp;lt; = 5 C- o Acres. ft. in. Feet. Gallons. Acres. Gallons. Loch Katrine, 3,000 Raised 4 Drawn 3 307 5,637,500,000 22,800 249,450

T.och Venachar, 865 Raised 5 9 Drawn 6 269 2,656,250,000 21,500 123,544 119 Loch Drunkie, Totals,. 83 Raised 25 416 750,000,000 1,500 500,000 3,94S 9,093,750,00045,800 The length of the aqueduct from Loch Katrine to Glas gow is about 35 miles, of which 27 may be considered as the aqueduct proper. The remaining 8 consist of two lines of cast-iron pipes, by which the water is conveyed from the large service reservoir at Mugdock to the city of Glasgow. The aqueduct is principally in tunnel or covered conduit, but there are three valleys which are crossed by iron syphon pipes of large diameter, and there are numerous aqueduct bridges of varied character, suited to the peculi arities of the districts in which they had to be constructed. The tunnels and covered conduits are 8 feet high and 8 feet wide, with an inclination of 10 inches in a mile, and are capable of conveying about 50,000,000 gallons of water in twenty-four hours. The syphon pipes across the valleys have an inclination of 1 in 1000, or about 5 feet in a mile, and it requires two pipes of 4 feet in diameter and one of 3 feet in diameter, to convey the quantity of water in a day which the aqueduct will deliver. The work required the greatest engineering accuracy and skill, and so perfectly have the lines and levels been kept, that it was only upon the closest examination that the joinings in the tunnels could be detected. The work was commenced in the spring of 1855, opened by her Majesty the Queen in October 1859, and finally completed in the course of 18GO. The cost of the engineering works of the aqueduct, in cluding the conversion of the various lochs mentioned into reservoirs, and exclusive of land, and of the distribution of the water in the city of Glasgow and its neighbourhood, was 008,000; but the gross cost of the water supply, in cluding the purchase of two water companies, distribution, and everything, has been, to May 1873, 1,750,793. The following description of the aqueduct was given by the engineer at a banquet given to him in Glasgow after the completion of the works : &quot; It is impossible to convey to those who have not per sonally inspected it, an impression of the intricacy of the wild and beautiful district through which the aqueduct passes for the first 10 or 11 miles after leaving Loch Katrine. From the narrowest point at which it was found the ridge between Loch Katrine and Loch Chon could bo pierced, the country consists of successive ridges of the most obdurate rock, separated by deep wild valleys, in which it was very difficult in the first instance to find a way. There were no roads, no houses, no building materials, nothing which would ordinarily be considered essential to the successful completion of a great engineering work for the conveyance of water; but it was a considera tion of the geological character of the material, which gave all the romantic wilclness to the district, that at once determined me to adopt that particular mode of construc tion which has been so successfully carried out. For the first 10 miles, the rock consists of mica schist and clay slate close, retentive material, into which no water per colates, and in which, consequently, few springs are to be found. This rock, when quarried, was unfit for building purposes; there was no stone of a suitable description to be had at any reasonable cost or distance, no lime for mortar, no clay for puddle, and no roads to convey material. Ordinary surface construction, therefore, was out of the question ; but I saw that if tunnelling were boldly resorted to, there would be no difficulty, beyond the cost and time required in blasting the rocks, in making a perfectly water tight and all-enduring aqueduct ; there would be no water to hamper and delay us in the shafts and tunnels, and little would require transporting through the country but gunpowder and drill iron. This course was therefore determined upon, and my expectations have been realised to the very letter. The aqueduct may be considered as one continuous tunnel. As long as the work continued in the primary geological measures, we had no water ; and even after it entered the Old Red Sandstone, and where it subsequently passed through trap rock, there was much less than I expected ; so that our progress, at no part of the work, was ever materially interfered with by those incidents which usually render mining operations costly and uncertain.&quot; The rock, however, especially the mica slate, proved extremely hard and difficult to work. At several points along the side of Loch Chon the progress did not exceed 3 or 4 lineal yards in a month at each face, although the work was carried on day and night. The average progress through the mica slate was about 5 yards in a month. In drilling the holes for blasting, a fresh drill was required for every inch in depth on the average, and about sixty drills were constantly in use at each face. The cost of the gunpowder alone, consumed in the first 7} miles of the aqueduct, was 10,540, and there were about 175 miles of fuse burned in firing it. The average cost per yard of this length of the aqueduct was over 13, or 23,000 per mile. (Figs. G to 11, are cross sections of the aqueduct, showing the general construction in various kinds of ground.) The built and tunnelled part is all capable of passing 50,000,000 gallons per day. The aqueduct bridges over the ravines are somewlwt peculiar, varying in character according to the circumstances of the district. In the wilder and more inaccessible parts there are five extensive iron ones, varying in length from 124 to 332 yards, all of similar construction. (See fig. 12.) At the ends of these bridges, in the shallowest parts of the ravines, the aqueduct has a cast-iron trough supported on a solid dry stone embankment of the stone of the district, carefully set by hand ; the stone embankment being 9 feet wide at top, with a batter of 3 inches to the foot on each side. The deeper parts of the ravines or valleys are crossed by malleable iron tubes 8 feet wide by Gi feet high inside, supported by piers at intervals of 50 feet. The II. .-9