Chap. VIII.
B HIT AIX.
551
river I,en, a little above Bow Bridge, draws its water Trom above the influence of thetide, and is carried by an aqueduct into settling reservoirs, which are upwards of 18 acresin extent; it then flows into another, from which it is pumped up by steam-engines of suffi-cient power to throw up 11.293,776 gallons per day: the highest elevation is 107 feet. Inthe year 1820 the total quantity supplied annually was 29,516,333 hogsheads; and thecompany had laid down in the streets 400 miles of iron pipes, one half of which were inuse at one time. When the water is at rest any matter mechanically suspended in itsettles in the pipes, to avoid which, before the turncock gives the supply to any street, hestarts the end plug of the service for three or four minutes, and lets a part of the water runout, which removes the deposit. The number of houses served is 50,000, and there are asmany tanks and waterbutts in the district in addition.
It may be w r ell to remark, that the quantities given are not to be considered asfixed, they are necessarily daily increasing; but in the year 1826 the total annuallydistributed to the metropolis by these public companies amounted to 155,381,038 hogs-heads, the number of houses being 120,000, and the rental paid tor the same 175,890/.The daily supply is stated to be equal to the contents of a lake of 50 acres, 3 feet indepth.
Trent Waterworks, at Nottingham, were established in the year 1830, under the directionof Mr. Thomas Hawkesley ; 8000 houses are supplied by this company, and the expen-diture was about 30,000/. ; the water can be thrown to any level; the annual averagecharge is 7s. 6d., and the quantity supplied to each house is about 80 or 90 gallons perday, at a cost of not much more than a farthing. The greatest pressure at which thewater is kept upon the pipes is about 120 feet, but the average is not more than 80 feet.The pipes are charged so as to deliver water to the tops of all the houses within a properdistance of the superior reservoir : they are generally } 2 inch in diameter, and each foot inlength weighs 2^ pounds.
It has been estimated by Mr. Hawkesley that the company sell 1000 gallons of water atsomething under 3 d., and that the total or general charges, exclusive of the interest oncapital, amounts to 1 *42, or a little less than l.'/A ; this is made up by a charge of $d. uponthe quantity for salaries, taxes, rent, repairs, &c., another Jd. for attendance upon themachinery, and a trifle less than \d. to defray the cost of coals, hemp, leather, oil, tallow,repairs, &c.
The construction of the filter is thus described :—the reservoir, which lies on the banksof the Trent, about a mile from the town, is excavated in a natural stratum of clean sand andgravel, through which the water slowly percolates to a distance of 150 feet from the river.The adventitious solid matter is generally deposited on the bed of the river, from which itis washed away by the action of the stream. The river at times is exceedingly thick, andof the colour of tea, from the admixture of peat and other vegetable matters; but afterfiltration through the bed, the water becomes perfectly pellucid.
The reservoir being exposed to the action of the sun produces vegetation of the confervagenus, which is removed at intervals of about three weeks in summer, and six weeks inwinter, by pumping out the water and the use of the broom ; after which operation a pinmay easily be distinguished at the bottom, a depth of 9 feet. To prevent the smallcommunication pipes from being choked by the accidental introduction of leaves and otherextraneous substances, the water is drawn through large sieves of fine strainer cloth. Inaddition to the reservoir there is a filter tunnel, passing through a similar stratum for a con-siderable distance up the adjoining hinds, 4 feet in diameter, and half a brick thick, andbeing laid without mortar or cement cost only 10*\ per foot, including an excavation to thedepth of 12 feet.
Greenock Water Supply , under the direction of Mr. Thom, engineer. A company incor-porated by an act of parliament in the year 1825 undertook these works, and the reservoirsthey have formed contain 310,000,000 cubic feet of water, into which annually drains morethan double that quantity ; their capacity is calculated for the consumption of more thansix months.
There is above the town a filter, the basin of which contains one day’s supply of water tothe inhabitants; the conduit pipe is 15 inches square, perfectly water-tight, being of stonebuilt with cement; the cost was one-third of that of an iron pipe of equal capacity. In itcesspools are formed, into which some of the sediment is deposited in its course before itenters the three filters. Each of these are 50 feet in length, 12 feet wide, and 8 feetdeep, and the water percolates through them either upwards or downwards at pleasure.When it passes downwards, and the lodgment of the silt is considerable, hv shutting onesluice and opening another, the water is made to pass upwards with sufficient force to carrythe sediment with it into a waste drain. After tins is cleansed, the sluices are again changed,and the filter operates as before.
By this arrangement of the several beds, a return current of water may be forcedupwards, and thus cleanse them from the deposit; there is also less average pressure and
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