CHAMBERS-'S INFORMATION FOR THE PEOPLE. 



Woolwich, where 600,000 gallons daily were oper- 

 ated upon with the most satisfactory result. These 

 works are now given up, though for reasons quite 

 apart from any failure in the process. But numer- 

 ous water-works have since been erected (some 

 of them quite recently) by Mr Homersham, C.E. 

 London, for supplying water from the chalk 

 springs, softened by Clark's method ; for example, 

 at Castle Howard, seat of the Earl of Carlisle ; at 

 Caterham, Surrey, for the supply of Caterham, 

 Warlingham, and several neighbouring towns. 



Clark's process is not confined in its effects to 

 softening : it has a decided influence as regards 

 organic impurities ; for it not only removes the 

 active source of corruption which exists in all 

 chalk-water, as above explained, but the precipi- 

 tated chalk carries down with it a large proportion 

 of such organic matters as may be already present. 

 Several calico-printers in Lancashire have had 

 Clark's process in use for several years, for the 

 improvement of the quality of the water employed 

 in their works. 



In order to prevent the action of soft waters on 

 lead pipes, they have been made with an inside 

 lining of gutta-percha, and also of tin, but the use 

 of such preservatives has become by no means 

 general 



Conveyance, Storage, and Distribution. 



We need not enter into a description of the 

 engineering operations connected with the con- 

 veyance of water from its source to the town to be 

 supplied, beyond noticing, that when the source is 

 below the level of the houses, steam or other 

 power is necessary to lift or force the water to the 

 necessary height ; while in the case of the source 

 being higher than the place where the supply is to 

 be delivered, the water is conducted, should the 

 contour of the country be favourable, either in a 

 channel or culvert with a continuous descent, as in 

 the ancient aqueduct, or, should the undulating 

 nature of the track render the use of an aqueduct 

 impossible, cast-iron pipes following the inequalities 

 of the surface must be employed. The annexed 

 diagram represents an outline of this mode of con- 

 veyance ; where a is a lake or reservoir situated 



Fig. 2., 



in a mountainous district, and b a town separated 

 by several miles of irregular country ; the course 

 of the pipes is indicated by the dotted line, and 

 the pressure of the water at a suffices to make the 

 water rise at b to a height nearly equal to that 

 of the head. In many cases, both principles 

 are employed, the water flowing for the most part 

 in a gently sloping conduit, tunnelled through 

 hills where necessary, and being carried through 

 valleys in tubes descending and ascending an 

 inverted siphon, as it is called. The Croton 

 Aqueduct, which supplies New York, is carried 

 across the Manhattan Valley, upwards of 100 feet 

 deep, in this way. The Glasgow supply from 

 Loch Katrine flows mainly in a sloping channel 



504 



carried through tunnels and over bridges ; but 

 there are four miles of iron pipings across valleys. 

 The extent of the storage in reservoirs depends 

 on the nature of the source of supply. In utilising 

 the waters of a river or stream, the capacity of the 

 reservoirs depends on the variations in its flow : 

 as, if the discharge were uniform, or nearly so, 

 throughout the year, there would be no use in 

 having storage at all ; and in like manner, if the 

 winter floods are very great, and the stream in 

 summer very small, the amount of storage should 

 be very great; the object being to store up the 

 excess which is flowing in the river in the wet 

 season, and deliver it out for use when the natural 

 discharge of the river in summer is under the 

 requirements of the district to be supplied by it. 



The reservoirs should be deep, so as to prevent 

 vegetation ; and the distributing or service reser- 

 voirs should be roofed, to protect them from the 

 contaminations always to be found in the atmos- 

 phere surrounding populous places, as well as from 

 the action of the sun. 



In distributing water over a town, two different 



1 methods have been adopted, known respectively 

 as the intermittent and the constant systems of 

 supply. On the intermittent system, water is laid 

 on once a day, or once in two or three days, as 

 the case may be, and fills a tank attached to every 

 separate house, and from this tank the water is 

 drawn off as required. The feeding-pipe of such 

 a tank or cistern is provided with a ball-cock (see 

 fig. 3), which ingeniously shuts off or admits the 

 supply, as the cistern may be full or empty. On 

 the constant system, no tank is absolutely needed, 

 except for the supply of water-closets, but the 

 house-pipes are kept constantly charged. The 

 intermittent supply was until lately employed 

 everywhere in the 

 metropolis ; but it is 

 universally admitted 

 that the other sys- 

 tem is vastly supe- 

 rior in every respect. 

 The disadvantages 

 of the intermittent 

 practice have been 

 strongly set forth in 

 all the recent official 

 Reports on sanitary 

 improvement : the expense of the erection and 

 repair of cisterns, the trouble requisite to keep 

 them clean, the contamination of the water by 

 the neighbourhood of sources of pollution, the 

 frequent waste of water that occurs, the difficulties 

 imposed on the poorer class of tenements where 

 cisterns are not provided are a few of the objec- 

 tions urged against this mode of supply. 



One important advantage arising from the 

 constant system is the ease with which water can 

 be had in time of fires. The water being supplied 

 at high-pressure, all that is necessary is to affix a 

 hose to the water-plug in the street, when a jet 

 corresponding in height to the pressure is obtained, 



| which can be immediately directed against the 



I fire. 



The ratio of the supply to the population varies 



j in different tewns. In Edinburgh, it is 34 gallons 

 for each individual ; in Glasgow, it is 50 gallons. 

 This includes the water furnished to works of 

 various kinds. The eight companies that supply 

 London pour into the city and suburbs not much 



Fig. 3- 



