Chap. XVIII.
SUPPLY OF TOWNS WITH WATER.
1211
Where the establishment is small, the forcing-pumps which raise the water are workedeither by horses, a water-wheel or steam-engine; but in large works the latter is usuallypreferred.
It has been before observed that when pipes were first laid down they were bored out oftimber, and the taper end of one was inserted within the other, which method did not per-mit of pressure being exercised. The introduction of cast-iron pipes, united by Ranches ateach end, screwed tightly together, with lead and other stuffing, has enabled mains to beformed perfectly water-tight: when inserted one within the other, or simply screwed toge-ther, a variation in the temperature will in a length of 300 feet produce in winter a con-traction sufficient to tear them asunder, some play being absolutely required at the joint.
The materials for closing the joints of the mains and pipes is now generally the bestDantzic fir, cut into shocks of 9 inches in length ; these are worked with an axe, or split intopieces 2 inches wide, and ^ of an inch thick, worked into the proper shape by spoke-shaves,so as to suit the curvature of the socket, as well as the convexity of the pipe to be insertedwithin it: a piece of fir, 9 inches in length, worked and cut into two, forms a pair ofwedges.
The joints are thus made : the wedges are first placed close to each other in the socket,and bv means of a set applied to the end of each they arc driven tight, and cut off close :should any escape of water take place, a wooden spile is driven in to stop the leak.Another, though more costly method is that of introducing first some gasket, and drivingit tight, to prevent the melted lead from passing; then by means of a clay mould running itwith lead, and afterwards setting up the joints. Pipes of various bores with wood jointsare found to resist any pressure to which they are ordinarily subjected, and less likely torequire reparation.
Mr. Robert Thom stated to the Commissioners of Inquiry in 1843 that his plan forsupplving towns with water was first to obtain some natural basin, at a sufficient height,either in itself containing a large quantity of water, or into which a great extent of sur-rounding surface can be drained. This reservoir should be formed deep enough to main-tain the water at a low temperature, and prevent the breeding of insects and the growth ofvegetables, and capacious enough to hold at least four months’ supply : if it be not possibleto obtain a sufficient extent of drainage surface at one place, other basins must be soughtfor to form auxiliary reservoirs, and the waters conducted into the main reservoir byaqueducts furnished with sluices of a peculiarly simple contrivance. To facilitate thecollection of the water from the surfaces, catch-water drains must be made use of, andadvantage taken of any stream which may be accessible: from the main reservoir thewater is to be led by an aqueduct to some place near the town, where reservoirs can beformed at such a height that from them it will rise considerably above the highest houses.These two reservoirs or regulating basins are each to contain two days’ supply, and fromthem the water is carried into two or more self-cleaning filters, and from the filters into twodistributing basins; the regulating basins, filters, and distributing basins, being in juxta-position, and so arranged that one of each may be connected together, to form a set ofapparatus, two of which are required, that the one may be in use, while the other is cleansingor repairing. From the distributing basins, the water is carried through the streets bysupply pipes of iron, so placed that it shall always flow in one direction, entering at thehigher and wider end, and flowing to the lower: they are always kept full at high pressure,so that there may be a supply for every emergency.
Self-cleaniny Filters _That constructed by Mr. Thom at Paisley, with the pure water
basins attached, is thus arranged : the stone pipe II brings the water from the regulatingbasin to the filters, and iron pipes, p , communicate between the stone pipe or aqueduct andthe top and bottom of the filters.
A valve near the top of the iron pipe S P, at S, forces the water to enter on the top orat the bottom of the filter at pleasure. The filter is 100 feet in length, and GO feet inbreadth, divided into three compartments, which may either act together or separately, sothat when one compartment is being cleansed, the other two continue in operation. The siteof the filters is a piece of level ground, excavated to the depth of 6 or 8 feet, with retainingwalls all round, joined with cement, and puddled behind, so as to become water-tight.The bottom is laid about a foot deep with strong stiff puddle, over which is a pavementso cemented as to be impervious to water. The whole of this bottom is then dividedinto drains or spaces, 1 foot wide, and 5 inches deep, by means of fire-brick laid on edge,and covered with flat tiles of the same material, perforated with small holes, like thoseused in a kiln for drying oats. These holes are placed very near each other, and arerather more than -jL of ar. inch in diameter ; there is also a space of ^ of an inch left openb. tween the ends of the bricks, which support the perforated tiles, and their upper edgesare little more than 1 inch broad, in order that there may be no space without holes, andnothing to prevent the water spreading equal')* over every part of the bottom of thesedrains. This is particularly necessary when the filters are being cleaned by the upwardmotion of the water. The perforated tiles or plates are covered to the depth of 1 inch