The water supplied to houses is, generally speaking, conducted front the street-mains to the cisterns, and thence distributed where required by means of leaden pipes, on account of the ease with which they eau be bent, so as to accommodate themselves, to the coustructiou of the house. Some waters, however, especially those containing free carbonic acid gas in suspension. act upon the lead with remarkable energy ; and instances of lead poisoning are by no means uncommon when the waters distributed are remarkably soft. When waters exposed to this danger must be used, it is necessary to employ either wrought-iron, or tin, or cuniposition servicespipes; but these waters are far (rum being ineocuuus, even to these substitutes for the more flexible material, lead. The only ether general remarks to lie made with respect to house distribution of water are : 1, that the apparatus for drawing the water should be of such a nature as not to produce a hydraulic jar on its being opened or closed; 2, that the pipes should not be placed so as to be exposed to the permeation of gases. or to the effects of heat or of frost ; 3, that they should nt all tittles ho accessible for examination and repair. The thickness of service-pipes may be calculated upon the formula x in which x = the thickness sought, p es the pressure c—r in Ilia per superficial inch, r = the radius or half the internal diameter of the pipe in inches, and e = the cohesive strength of the metal per superficial inch. 3lr. Ilawkaley makes the thickneesea of Ilia cast-iron pipes equal to Vd, or about of the square root of the diameter. In practice, lead-pipes are made equal to ?lit iu small pipet, and to in very large ones.
The quantities of water required for the various details of domestic distribution are as follows :— Generally speaking, the charge for a house supply is based upon its estimated rental, in England at least, and it very rarely attains 5 per cent. on that value. But an additional charge is made whenever more than one water-closet is in the house ; when fixed baths are used; for coach-houses and stables, according to the number of carriages and horses; and for gardens. Such trades as tanners, fellmongers, hair washers, curriers, glue-makers, dyers, hatters, brewers, distillers, manu facturers, inns, public baths, and are considered as large consumers, and are usually supplied with water by meter. The price under the latter arrangement is, in London about 6d. per 1000 gallons. The supply of water for the extinction of fires is, in this country, cast upon water companies; and it appears that in the New River district of London there is at least one fire-plug in every length of sub-main equal to 73 yards, on the average ; on the great mains there is a plug to every 157 yards. For the purpose of street-watering, stand-pipes ought to be placed at distances of about 500 yards apart: in our climate it appears that the streets require watering between 120 and 135 days in the course of the year. sometimes even twice in the day. The quantity of water varies with the nature of the road-surface; and where nicety of calculation is required, it may be considered that 600 square yards of macadamised road will only require one ton of water, whereas 400 square yards of paved road will require that quantity.
It may be added, that the street-plugs (the borne fontaines) used in Paris to cleanse the channels are usually placed at distances of about 140 yards, and that they discharge at intervals during the day a total quantity of water equal to 650 gallons each : more than half the total supply of Paris is thus poured into the streets.
It would be idle to give any statistics of the capital invested in water-works, either in England or elsewhere, because new works of this description are being coustantly undertaken. In London alone the capital invested in the various Water-Works Companies cannot be considered to be much less than eight millions sterling ; and, as a general rule, it would appear that the average cost of conducting a water supply to the doors of the houses in a town varies between 2/. and 3/. per head of the population ; whilst the house distribution gives rise to a further outlay varying from 4/. to 20/. per house, according to its character and to the system of distribution adopted. In newly established works, the constant-delivery system admits of considerable economy in this respect. Of late years, also, it may be added that more attention has been paid than was formerly the case to the pressure under which water is delivered in towns ; and that, to a great extent, the distinction between high and low service has ceased to exist. In new works the mains are always laid under such conditions of pressure upon the water they contain as to cause the latter to flow in the loftiest rooms of the loftiest houses in the respective towns.
In Itobbson's Mechanical Philosophy,' in Playfair's Lectures,' in Jamieson's ' Mechanics of Fluids,' Weisbach's ' Mechanics of Machinery and Engineeriug,' D'Aubuisson's ' Hydraulique; Ceniey's Essai sur les Moyens de conduire et Meyer lea Eaux,' Darcy, ' Sur lea Fontaines Publiques do la villa de Dijon,' Dupuit's ' Essai sur la conduits et In distribution des Faux,' and dispersed throughout the various Blue Books and Parliamentary Evidence upon the subject of town water supplies, much information upon the practical details of that branch of the municipal service is to be found. Unfortunately. there is no work in English, treating this subject exclusively, which can be considered to be of any value • and the reader cannot be too seriously warned against accepting, any of the doctrines lately promulgated here " by authority." The French writers upon hydraulics aro still those who are to be the most implicitly followed in matters of theory ; the practice of the best English engineers in matters of working detail must be consulted, in spite of the official censure passed by a class of empirics who seem to have objected to eminent engineers solely because they were eminent. Dwyer's ' Hydraulic Engineering,' Neville's Hy draulic Forinuke; Downing's 'Practical Hydraulics,' and Beardmore'e Hydraulic Tables,' may also be consulted with advantage.