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WATERWORKS AND WATER, Issue 15654, 19 November 1914
WATERWORKS AND WATER
I ADDRESS BY MR M'CURDIE. On Tuesday evening of this week the lecturer befoie the 'technological Branch of the Otago Institute was Mr D. W. II M'Curdie, city engineer. He pointed out the uses of water—for domestic purposes, for nee in trades, for irrigation and power and as an ornament. A photograph of Jacob's Well was put on the screen. It was described as one of the oldest public waterworks, still in regular use. The only apparent change was that the girls now chiefly use kerosene tins in place of tho more classic earthenware vessel. Underground water was a main source, of supply in Palestine, so all the old patriarchs were we'l-sinkers. in a modern schema or" any magnitude a surface catchment ii ; ncces-sa'-y. Th'smay he a sy.stem of email streams fioni a mountain region, or a river, or a lake, or .it may be tlie roif of a house. In the last care the dam ifc a tank or a number of tanks. Earthen clams were *hown on the screen, including cases from Japan, the United States, and elsewhere. It was explained that in English practice an earthen dam is made watertight by a core of very compact puddled clay in t!:e centre. In India this core is on or near tho water face. . In the United States earthen damn are fonstructeci on what, is called the hydraulicfill sv.-tom, u:id'»r which the whole embankment is made up of wot slush, quarried and worked into slurry at some convenient point abrwe the level of the dam, and washed on to the site through fluming. No core is used in these dams, the whole body of the material settling down into a verv compact niiifß. The fust operation of the. engineer in choosing a site for a dam is to see that the foundation is firm and watertight. Then a careful contour plan is made, showing by contour lines, or lines of equal height, ihe exact shape of the surface. From these lines and the information sained from borings the whole of the finished dam is carefully planned before work is begun. Water is usually drawn off from these dams by a tunnel under the embankment or alongside the embankment. It was explained that more earthen dam? fail through defects in the. tunnel than from all other causes. Tn the Sullivan dam, now under < on-true* ion by the City Coun. cil in the Leith Valley, there will be no tunnel, the water being made to rise over the dam under the influence of a hydraulic jet. When Mr M'Curdie was dealing with masonry dams, all the important masonry and concrete dams in the world xroro shown on the screen, all drawn to the one sc.ilc for purposes of com par if on. It was noted that the old Spani-h and Moorish dams did rot lack anything in point of stability, tbeic being about, three times as much masonry in them as a modern engineer would use. 'Hie Tdaburn dam was the New Zealand contribution to tho list. The Austin dam was illustrated by photographs, just before, and just after Up destruction by a flood in ISOO. Tbe advantage of curvature. wa« explained and illustrated in the Boar Valley dam in California and the Craig Goch dam , in Wales. The Valley dam is a wall 63ft bigh and 2'fl to 3ft thick at. top, | with no stability at all but itfi slicht rrrvnture. American engineers have railed the fact that it- has stood and held water for so many years the eighth wonder of the world. Water pipe? in bamboo, timber, castiron, and ftcel. riveted and welded and f-olid-drawn. were described and illustrated, and a wooden pipe main 13ft 6in in diameter was «hnwn. Bacteria found in watej v-ere shown. also various forms of incrustation in pipes and the means of removing til© same. Mr M'Curdie also speke about filters. The modern rapid filter method was described and explained by meanF of a, plan of a, modern English filter installed and worked on thU principle with great success. This was interesting, inasmuch as it illustrated exactly the plan proposed to be installed by the Dunedin City Corporation for purifying the water in the Moray Placo Baths. These filters work at about 50 times th:? rate of the old slowmoving sand filter, and are more reliable, inasmuch as the '>! d fraud filter was very liable to Have the fir face film on the sand scratched into holes by the- larva* of water msecis, thus allowing tho wat-.T to pass through unfiltered. Old Rome aqueducts were shown, and contrasted with the modern methods of dealing with the same quantity of water coming through a pipe underground. A number of water towers were shown on tho scr«en, and their uses explained ir. a- most interesting manner. towers aro necessary in a fat country. ! The wit ei- is forced into the tower, and I from there delivered all over the town under pre?c uroi ,j uo to the height of the tower. Tbe Invcrcargill water tower was chosen as one. of tin examples. Aeration was alto spoken about—the aeration of water from underground sources. Why aeiate? For several reasons. Water from underground sources I is often tainted with iron, and although this is not poisonous it gives trouble to the women on washing day. John Buskin points out that is beautiful in a. brick wall or jn a Marfelllee-tiled roof, or en the bloom of a maiden's cheek, or on tho more finished face of a duchess, but it plava the den! with whit© sheets. Exposure In a jet or waterfall or spray for a small portion of a. second is sufficient to oxidise the iron and send tho water away clean, 'l'hat is what aeration does. Aeration ako eliminates color, taste, and .smell. Filtration alone will not accomplish this, but filtration and aeration will. The lecturer went on to apeak of what in known as "the turnover of the water." In climates where there aie extremes of heat and cold there lakes place a turnover of the water in tho reservoirs every .spring and autumn. During the winter ttie cold water (at- a temperature lower than flOdog) etayti nt the top, on account of its lesser specific giavity. With the approach of spring the temperature, of tbe j top layer rises tilt it becomes the same as the'bottom layer. Then, with the first gale, the whole, is mixed and turn?d over, and the stirring causes inconventenc-e to nose and palate. The same process, reversed, occurs -it tbo end of summer. All there- happenings relate to dams over 40ft deep- If shallower than that the stirring m'Ocess goes on all the time. In the various calculations made by the lecturer he used the metric system, and he showed how it worked in tho measuring of water, thus: 20 drops = 1 drip= 1 cubic centimetre. ]OO drips = 1 dram. 10 dram.s = 1 drink = 1 litre. 4 drinka »» 1 gallon. The abore is a mens o-utlino of what ! proved to be a most interesting address.
WATERWORKS AND WATER, Issue 15654, 19 November 1914
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