DESCRIPTION OF THE SOURCES OF SUPPLY AND METHOD OF FILTRATION (IF ANY). LONDON COMPANIES. The Chelsea Company's water, Grand Junction Water Company's water, the Lambeth Company's water, the Southwark and Vauxhall Company's water, and the West Middlesex Company's water are all pumped from the Thames, but at somewhat different points. The mode of filtration also differs considerably. The following are the particulars of these supplies : The Kent Water Company draw their supply entirely from deep wells in the chalk. Of these there are two at Crayford, 150 feet deep, which yield over 2 million gallons per day; and an additional one, 150 ft. deep, has been sunk at Orpington. Three others at Deptford, and two at Shortlands, are 250 feet deep; and one at Plumstead is 500 feet deep. The water does not require filtration. The Company have 9 reservoirs, the whole of which are covered. The Company supplies an estimated population of 303,300 people. New River Company draw their supply partly from Chadwell Spring, near Hertford, which produces between 4 and 5 million gallons daily; partly from the River Lea, from which (at a point also near Hertford) they take from 15 to 22 million gallons daily; while they have also deep wells at several other places, from which large further supplies are drawn from the chalk as need requires. The subsiding and storage reservoirs for unfiltered water are capable of holding nearly 170 million gallons, and the covered service reservoirs for filtered water about 30 million gallons. The filtering beds consist of a 2 ft. 8 inches thickness of sand, or a 3 ft. thickness of gravel or other supporting material. The average rate of filtration is about two gallons per hour per square foot of filtering area. The Company supplies an estimated population of nearly one million people. East London Company draw their supply from the River Lea, at Chingford. They have also the power of taking a certain quantity from the Thames, at Sunbury, which they occasionally exercise. The capacity of the storage and subsiding reservoirs for unfiltered water is about 605 million gallons, and of the reservoirs for filtered water 12 million gallons. The filtration is effected through sand, 2 ft. 6 inches; coarse gravel, 1 foot; boulders, 1 foot. The average rate of filtration is about 1.3 gallons per hour per square foot of filtering area. The Company supplies an estimated population of about 960,000 people. Southwark and Vauxhall Company.-The intake is from the Thames at Hampton, almost adjoining that of the Grand Junction Company. The reservoirs for unfiltered water are capable of holding nearly 66 million gallons, and those for filtered water about 18 million gallons. The filtering material consists of Harwich sand, 3 feet; hoggin, 1 foot; fine gravel, 9 inches; coarse gravel, 9 inches. The average rate of filtration is about 1.5 gallons per hour per square foot of filtering surface. The Company supplies an estimated population of 684,000 people. West Middlesex Company.--The intake is from the Thames at Hampton, very close to the intake of the Grand Junction Company. The reservoirs for subsidence and storage of unfiltered water are capable of holding nearly 92 million gallons, and the reservoirs for filtered water about 11 million gallons. The filter beds consist of Harwich sand, 2 ft. 3 inches; Barnes sand, 1 foot; gravel, 2 feet 3 inches. The average rate of filtration is about 1 gallon per hour per square foot of filtering surface. The Company supplies an estimated population of nearly 430,000 people. Grand Junction Company.-The intake is from the Thames at Hampton. The capacity of the subsiding and storage reservoirs for unfiltered water is nearly 641 million gallons, and the capacity of the reservoirs for filtered water about 24 million gallons. The filter beds consist of layers, commencing from above downwards of Harwich sand, 2 ft. 6 inches; hoggin, 6 inches; fine gravel, 9 inches; coarse gravel, 9 inches; boulders 1 ft. The average of filtration is nearly 13 gallons per hour per square foot of filtering surface. The Company supplies an estimated population of 890,000 people. rate Lambeth Company.—The intake is from the Thames at Molesey. The reservoirs for unfiltered water have a capacity of 125 million gallons, and those for filtered water a capacity of about 30 million gallons. The filtering beds consist of Thames sand, 3 feet; fine gravel, 1 foot; coarse gravel, 3 feet. The average rate of filtration is 3.5 gallons per hour per square foot of filtering area. The Company supplies an estimated population of 468,000 people. Chelsea Company.-The intake is from the Thames at Molesey. The capacity of the reservoirs for the storage of unfiltered water is 140 million gallons, and for filtered in water 11 million gallons. The filtering beds consist of Thames sand, 3 ft. 3 inches; shells, 8 inches; gravel, 4 ft. 6 inches. The average rate of filtration is about 2 gallons per hour per square foot of filtering surface. The Company supplies an estimated population of 225,000 people. It may be convenient to tabulate the details as to these London waters thus : : PROVINCIAL TOWNS. Cambridge. The supply is obtained by means of a tunnel in the chalk rock, at Cherry Hinton, about two miles from Cambridge, from whence it is conveyed in cast-iron pipes, and pumped up to a covered service reservoir for the supply. Canterbury.--This water is derived from springs in the chalk, which in this neighbourhood is about 700 feet in thickness. There are two wells, and the first water fissure tapped was at a depth of 328 feet below the surface, or 290 feet below sea level. The temperature of the water as pumped is 51° F. The water is softened by Clark's process, in tanks, holding 100,000 gallons each, and after the subsidence of the carbonate of lime, the clear water is pumped up to covered reservoirs, from whence it descends by gravitation to the city. Attempts, which will probably be successful, are being made to recalcine the deposited carbonate of lime. Exeter. The water is drawn from the River Exe, above the confluence of its tributary the Culme. A conduit conveys the water from thence to the pumping station, from whence it is pumped to the reservoir, filters and distributing reservoir at Danes Castle; another reservoir for the high pressure service being placed at a higher level. The supply is intermittent. The sewage of Tiverton, which is situated about 10 miles above the works, is a source of pollution to the river. The River Dart, the water of which is highly coloured with peaty matter, discharges into the Exe, near Tiverton, which again interferes with the purity. The filtering material used is Haldon sand, which is composed of coarse grains of quartz derived from the disintegration of rocks, and sand from Paignton, derived from the degradation of rocks belonging to the new red sandstone series. A sediment left on the sand is sufficient to necessitate the removal of three inches of the surface of the filtering beds every two months. Huddersfield is supplied from Blackmoor Foot reservoir, which has a capacity of 700 million gallons. This reservoir is fed by two conduits, having a total length of about seven miles, one running from the millstone grit moorlands on the Marsden side, the other through similar moorlands on the Merton side, where it takes in a mountain stream, which supplies a large proportion of the water. The conduits are cut through beds of peat, shale and clay. The shale is in places somewhat ochrey, but the clay is remarkably free from compounds of lime and magnesia. King's Lynn is supplied from a stream called the Gaywood River, a portion of which is diverted into the waterworks at a short distance outside the town, and drawn simultaneously through a pair of filter beds. The river which brings the water to the town is about seven miles in length, and the water is mainly derived from one great water-bearing stratum in the chalk; the river passes through the oolites, touches the upper green sands, and finally traverses the silt at Lynn. Leeds. The supply is collected in the valley of the Washbourne, about 15 miles northwest from Leeds; the gathering grounds are chiefly moorlands covered with peat and heather; a small portion of the land is pasture. The substrata are shale in some parts, but chiefly millstone grit. Description of SOCIETY OF PUBLIC ANALYSTS. Analyses of English Public Water Supplies in January, 1881. All results are expressed in GRAINS PER GALLON. Kent Co. East London Southwark &' pale blue 0040 0100 16.8° 3.8° 20 05 .... c., faintly tinted none greenish .84 traces none 1.35 h. traces pale yellow none 1.24 traces 1690 0005 00500020 0440 17.5° 5.0° 23.80 sand, vegetable debris none sand, vegetable debris satisfactory Amorphous organic matter none none [organisms A. Dupré. none traces mineral none trace veg. matter none none none vegetable debris {animal and vegetable] debris none vegetable matter none } J. Muter. } W. Johnstone. Abbreviations: c., clear; f., faint; h., heavy; v. h., very heavy. ON THE IDENTIFICATION OF THE COAL-TAR COLOURS.* BY JOHN SPILLER, F.C.S. DYERS and others who are in the habit of using the coal-tar colours are familiar with a number of chemical reactions by which the members of the series may generally be classified and identified. Differences are remarked in their relative affinities for various sorts of fibres, some colours being taken up freely by silk, others fixing better upon wool, and some few, like saffranin, exhibiting a special affinity for cotton. Again, as with the yellows, great differences are observed when the operator proceeds to work with a free acid or a weak alkali in the dye-bath. Primrose (naphthaline yellow) requiring the former, but not so with phosphorine (crysaniline yellow), which demands a neutral or even slightly alkaline bath. By the study of these conditions, aided by a few characteristic tests, it is often possible to identify colouring matters of unknown or doubtful origin, and it is with the view of extending the number of such readily available tests that I recommend a more frequent appeal to the colour reactions with sulphuric acid. For this purpose but small quantities of material are required, a few grains serving to impart a distinct colour to a comparatively large bulk of sulphuric acid, and the resulting indications are in many cases both specific and permanent. Oil of vitriol, which so readily destroys nearly all organic structures, does not carbonise any of the coal-tar colours, or does so only under severe conditions, as at high degrees of heat. Even indigo and madder, although of true vegetable origin, are known to yield up their colouring-matters to sulphuric acid, the old process of dyeing depending upon this fact. In the manufacture of garancine from madder the woody fibre and organised tissues are destroyed by the action of sulphuric acid, whilst the alizarin glucoside survives, and with it Turkey-red goods may be dyed.† Instances might be multiplied as proof that colouring-matters, both natural and artificial, resist the attack of oil of vitriol, and the large class of sulphonates (Nicholson blues, "acid roseine," &c.) may be cited as establishing the fact that colouring-matters are not so destroyed, but form combinations with sulphuric acid. If, then, the body under examination be dissolved in strong oil of vitriol, a colour-test is at hand whereby useful inferences may be derived as to the nature of the dye, and often its exact identity disclosed. A few direct confirmatory tests may then be applied. most remarkable colour reactions are the following : The Grass-green, becoming indigo-blue on strongly heating. Golden yellow. Primrose (napthaline yellow)...... Difficultly soluble, first yellow, and colour discharged Crysaniline Aurin Atlas orange Atlas scarlet on heating. Yellow or brown solution, of marked fluorescent character. Yellowish brown, non-fluorescent. Rose colour, turning to scarlet on heating. Scarlet solution, very permanent on heating. * Read before the Chemical Section of the British Association, Swansea Meeting. † See W. H. Perkin's "History of Alizarin," Journ. Society of Arts, May, 1879. |