310 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



meeting such cases, or modifying such pressure P— In such case I shoiiM en- 

 deavour to bring Ihe leading main from the higher part of tlie city to tlie 

 lower lay off the sul^-mains and services bv lines of equal altitude, and re- 

 duce tlie pressure at proper decrements of height by a loaded valve, as shown 

 by the sketch." 



Filtration. 



Mr. Hawksley stated that with regard to filtration, that it is always advan- 

 ta"ccus to filter water vOiich is not naturally bright, to clear it from matters 

 ]i -Ul in suspension. If the extent and tliickness of the filtering-bed be very 

 considerable, prior subsidence may be altogether dispensed with ; but if the 

 surface be limited, and the thickness small in respect to the tjn.an!ily of water 

 to be treated, as is usually the case when artificial filters are employed, then 

 it becomes necessary to resort to previous subsidence. There are particles so 

 fine and minute, as to be incapable of being deposited by the force of gravity, 

 tliounh they may be detained by filters, if the operation be slowly and cau- 

 tiously conducted. At Nottingham, tlie construction of the filter is this ; 

 the reservoir which lies on the banks of the Trent, about a mile from the 

 town, is excavated in a natural stratum of clean sand and gravel, through 

 which the water slowly percolates to a distance of 150 feet from the river. 

 The adventitious solid matter is gently deposited on the bed of the river, from 

 which it is washed away by the action of the stream. Sometimes the water 

 comes down the river exceedingly thick, and discoloured by peat and other 

 ve-'etable matters ; it is sometimes of tlie colour of tea : neverllieless filtration 

 throU"h the bed of 150 feet renders the water perfectly pellucid. When the 

 bottom of the reservoir has been bright from a recent sweeping, a pin may be 

 seen at the depth of eight or nine leet. The reservoir being e.vposed to the 

 action of the sun produces vegetation of the conferva genus, which is removed 

 at short intervals of about three weeks each in summer and of about six weeks 

 in winter, by pumping out the water and the use of the broom. To prevent 

 the small communication-pipes from being choked by the accidental intro- 

 duction of leaves and other extraneous substances, the water is drawn through 

 lar"e sieves of fine strainer cloth. In addition to the reservoir there is a filter 

 tunnel passing through a similar stratum for.a considerable distance up the 

 adjoining lands. This tunnel is four feet in diameter, and half-brick ibick, 

 and being laid without mortar or cement, cost only 10s. a foot, including ex- 

 cavation to a depth of 12 feet. The office of the reservoir, in addition to the 

 filtration through the bank, is to receive and accumulate the water during 

 the time the engine is not at work. The tunnel is formed simply for the pur- 

 pose ot filtration, and it has the advantage of not exposing the water to the 

 action of the sun. — The water is transmitted to the upper reservoir by an en- 

 gine along a main-pipe, which passes through the middle of the town and 

 supplies all the inferior pipes in its course. The upper reservoir, placed at 

 the extremity of this pipe, receives tlie excess of water pumped by the engine, 

 and returns it down the same pipe so soon as the engine ceases to act, and 

 hence a constant supply is maintained without difficulty, trouble, or expense. 

 The distance of the .site of the filtering and subsiding reservoirs would not 

 occasion such expense or inconvenience as to prescribe close limits. The en- 

 gineering difficulties would be very insignificant, and the expense really 

 trifling in comparison with the resulting advantages. Not the least of which 

 would be the securement of an unfailing supply of pure water for several ages 

 to come. 



If for the supply of the metropolis it were found desirable to take up the 

 water of the 'ibamesin its full purity above Windsor, and erect filters or 

 subsiding beds thereabout, the probable expense of its transmission above 

 a supply taken up near the metropolis would be for the transmission 

 of 500 gallons of water per second two mains, eacli of 60 inches diameter, 

 would be requisite. The resistance from friction may be calculated from the 

 formula for long pipes 



Q'/ 



P = 



140 rf^ ' 



in which (P) represents the horse-power necessary to overcome the friction, 

 (/) the length of the pipe in inches, (Q) the quantity of water to he delivered 

 in one second, and {d) the diameter of the pipe. From this we ascertain that 

 the resistance arising from friction in pipes of the given size, and 25 miles 

 long, would require less than 450 h. p. beyond the force employed to raise the 

 water into an elevated reservoir. If this reservoir were situated at a height 

 of 220 feet, the steam power required to raise tlie water would be about 2000 

 nominal horses, and the total power to be employed in transmitting and rais- 

 ing 500 gallons of water per second would amount to less than 2500 horses. 

 The cost of the main pipes would be about 1,000,000/- ; of the engines and 

 machinery, with some reserve of power, about 150,000/. ; and of the tanks and 

 reservoirs probably 200,000/. A first investment of 15s. per head, or Sti/. of 

 addition to the annual water charge of each of the population would there- 

 fore enable a constant supply of ihe purest soft water to be delivered at all 

 hours, and into every story throughout London, and that without injury to 

 the interest of the existing companies wdio might derive their su[iplies from 

 this common source. A very considerable economy of management and 

 working expenses w ould indeed result from this consolidation of engineering 



operations which would go far in reduction of the increased charge of 9r/. per 

 annum. 



Supply oe Water for Baths. 



Mr. Thomas Hawksley stated that he had been consulted in resppct io 

 public baths, and had been engaged in making some private baths.— On the 

 assumption that one hogshead, or 54 gallons of water, would suffice for the 

 ablution of each person, the cost of pumping and engine expenses for 100 

 persons per diem would be threepence, and the extra expense of filtration by 

 artificial means something less than 2d. more, — The expense of fuel for heat- 

 ing 100 hogsheads of water from a mean temperature of, say 52", for baths, 

 to blood heat, or say 98°, would require 270 lb. of Newcastle coal, which 

 would cost in London about 3s. In addition to this, a further quantity of 

 fuel would be required to replace the heat lost by radiation, evaporation, and 

 conduction, whicli would be subject to great variation according to circum- 

 stances. An equal quantity of coal would in general, however, be sufficient 

 for this purpose. On a larger scale there would be some saving. — The whole 

 expense of hot baths in numbers of not less than 100 per diem would stajaJ 

 nearly thus for each person for the single bath : — 



s. d. 



Water 0| 



Fuel OJ 



Attendance 1 



Interest on building and incidentals 1 



21 



The probable cost of maintaining a tepid swimming bath, suppose 80 feet 

 long and 30 feet wide, and of the average depth of 5 feet, and supposing 

 10,000 gallons of fresh water daily admited into it, would be for warming 

 that quantity of water, about 2 cwt. of coal, and it would probably in prac- 

 tice require 4 or 5 cwt. in addition to sustain the temperature of the bath. A 

 remunerative charge for the use of the tepid bath would probably be about 

 2d. per head, if taken by 200 or 300 persons per diem. 



Fountains. 

 With respect to the use of water for fountains, Mr. H. slated that a jeD d'c- 

 livered under a pressure of 36 feet through a plate pierced with a halt'-inclii 

 aperture, would deliver 900 gallons per hour to a height of 30 feet sr up- 

 warils, at an expense of 2id. per hour. An inch orifice would deliver four 

 times this quantity to a height somewhat greater, and would be charged about 

 8rf. per hour. 



Supposing the water works maintained by the town, and that it was deter- 

 mined to supply the public fountains at the expense of pumping only, a 

 half-inch jet would cost per hour, inchuling coals, wages, and the working 

 expenses of the engine, very nearly \d.^ or for a day of 14 hours. Id. per dVem., 

 anil an inch jet 2d. per hour, or 2s. id. per diem. This is the cost at Not- 

 tingham, where the water is raised 135 feet ; but under other circumstanices it 

 might be less ; and for the cost of jiumping only for small wayside fountains 

 delivering say one or two hogsheads of water per hour, would be \d. to irf. 

 per diem. 



Watering and Cleansing Streets. 

 Mr. H. stated that for watering, the rule of assessment is J<i. per square 

 yard of surface watered, if for small surfaces, and \d. if for extensive surlaces, 

 for the season. 



In the metropolis, the charge for water for watering tlie streets is some- 

 times 2W. per ton, and one ton it is ascertained will water so as to lay the 

 dust of GOO squaie yards of gravel or Macadamized roads, or 400 square yards 

 of granite paved roads. It appears that the number of days for which the 

 water is required to lay the dust is, on the average of 20 years' experience, 

 about 120 per annum. A common charge is %d. per square yard for the water 

 for a season. When the parishes perform the service, it is usually at from 

 \\d. to 2d. per pound on the rental. Now what would be your charge of the 

 expense of water per house of 20 feet frontage for the season ?— Our charge for 

 the supply of water to a street one mile long and 15 yards between the kirb- 

 stones, would, by our charge per ton, be 16/.; for twice over, 32/.; whicli 

 with houses of seven yards frontage would be a charge of Is. 6d. per house, or 

 allowing for occasional vacant spaces in the row of houses, say 2s. per house 

 for the supply of water during the like season. — For watering streets twice 

 per diem, 1 think one man might, with proper and properly-placed apparatus 

 for jets, eli'ect the watering of about one mile. Supposing the wages to be 20s. 

 and expense of hose 10s., or altogether 30s., per week, the additional expense 

 for labour would be about ls.6rf.per annum (omitting the Sundays), or allow- 

 ing for vacancies, say 2s. 



It IS sta'ed that an ordinary sweeper usually sweeps 1000 square yards of 

 pavement per dium. and a good labourer of the class about one half more, and 

 that the expense uf sweeping by hand labour is between 2/. and 3/. per mile of 

 street 15 yards wide. Have you had any observations of the labour and ex- 

 pense of the more eflfectual mode of cleansing granite or wood pavement by 

 scouring with a jet?— No precise.obscrvatioas. 1 have seen an open space of 



