1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



309 



The price of fuel will vary greatly in .liflerent places. And the description 

 of engine will also vary, and influence the consumption of fuel. 



The dillerent descriptions of engines, and prices of fuel, taken in relation lo 

 each other, will afford the result shown in tlie.above table, and they will stand 

 nearly as tollows : — 



Description of Engine. 



1. H.P. — Double powered, non-condensing .... 



2. B. and W. — Double powered, condensing . . 



3. B. and VV. — Single powered, condensing .... 



4. Cornish. — Double powered, coudensingt .... 



5. Cornish. — Single powered, condensingf .... 



6. Cornish. — Single powered, condensingf .... 



7. Taylor's Cornish. — Single powered condensingf 



steam 

 Pressure. 



30+0 



3 J + atmos. 



3J + atmos. 

 30 + atmos. 

 30 + atmos. 

 45 + atmos. 



Cost of Fuel, 



25 

 20 

 16 



12 

 9 

 6 



" Then is the relative economy of these engines such that, for instance, the 

 engine No. 6 would perform the same amount of work w ilh 3s. worth of fue', 

 to do which the engine No. 2 would require 2os. worth ? — Yes; but against 

 this advantage must be placed the vastly greater first cost the engine No. 6. 

 and its much greater liability to accident. By the use of the Cornish engine 

 No. 6 in Jplace of the Boulton and Watt engine No. 2, a saving of nearly 

 0'2d. per thousand gallons would be effected in the fuel account, hut the 

 capital account would be increased fully 0-\d. ; the resulting economy to set 

 against increased risk would, therefore, not exceed a twenty-ninth part of 

 the whole charge. I should, therefore, be in general disinclined to recom- 

 mend the adoption of the Cornish engine, except, perhaps, in the case of 

 works of such great extent and so arranged that the public would not be in- 

 convenienced by the stoppage of a single engine." 



"The cost of construction of the works at Nottingham, is something less 

 than 1/. per individual, supplieil by the Trent Water Company, but if that 

 Company had the sole supply of the district over which its pipes are laid, the 

 cost would not exceed 15s. per individual. The expense attendant on the 

 supply of water and management of the works amounts to about 44 per cent, 

 on the income, which is slightly less than the proportion of the like expense 

 in London.'* 



" You have stated that, on the system of constant supply at high pressure, 

 smaller instead of larger mains would suffice. It has been stated that at one 

 town, where a high pressure was put on old mains and distributary pipes 

 constructed lor a low pressure, the pipes which burst were very few, and the 

 inconvenience (which it was anticipated would be very great) was incon- 

 siderable. Does your practical experience enable you to express a confident 

 opinion that the mains and ordinary distributary pipes for the system of 

 periodical supply would not be required to be extensively superseded, and 

 others of greater thickness substituted for the application of a system of con- 

 stant supply, under a system of moderate high pressure, such as that con- 

 templated ? — Yes ; the amount of pressure does not practically enter into the 

 determination of the thickness of the metal of main pipes. Any thickness at 

 which mains can in the regular course of foundry business be cast will afford 

 many times the strength requisite to retain water under a pressure of 150 

 feet. In fact, pipes are proportioned according to the difhculty of running 

 the metal and adjusting the core ; and, in practice, it is customary to pre- 

 scribe a thickness of, at most, one-tifth the square root of the diameter 

 ( • \8 V d ), a. proportion which has no reference whatever to the strain arising 

 from the pressure. Pipes are now cast lighter than formerly, although the 

 pressure under which water was usually transmitted has been increased. 



" Be so good as to explain the method by which you ascertain the dimensions 

 of pipes for a constant supply to the attic stories ? — Assuming the case of a 

 street of houses 600 yards long, I proceed thus :— I first ascertain, perhaps, 

 by the parish books, the numbers and rentals of the houses; I then estimate 

 the consumption of water in each house in gallons at 12§v'rentin poundl, 

 which I find by experience to afford a result as accurate as the nature of thg 

 inquiry will permit. 



" This gives for houses of 6;. rent 40 gallons per diem ; lOt. rent 56 gallons 

 per diem ; 20?. rent 88 gallons per diem ; 50/. rent 163 gallons per diem ; 100/. 

 rent 260 gallons per diem, 200/. rent 410 gallons per diem; 500/. rent 756 

 gallcns per diem. To obtain a proper practical taper, I divide the length of 

 the pipe into portions of about 200 yards, and assign to each the quantity of 

 water to be conveyed ; thus 



Final 200 yards . . 13,000 gallons per diem. 



Middle 200 yards 11,000+13,000 = 24,000 „ 



First 200 yards 8,000 + 24,000 = 32,000 

 I next consider that nearly the whole of the water will be consumed in the 

 four or five hours elapsing between breakfast and dinner : to err on the safe 

 side, I assume the delivery to take place in four hours, and that the whole of 

 the water taken off from each length has to be passed to the end of that length- 



t Expansive action, 



It will sometimes happen that the reservoir from which the supply is obtained 

 is nearly on the level of the attic stories, and that in consequence perliaps not 

 more than four feet of bead can be allowed on each length of 200 yards to 

 produce the velocity and overcome the friction: allowing this quantity in 

 the case assumed, I shall be enabled to apply the formula, 



Vt-- 



which I have found to apply with great exactness : in this formula (q) repre- 

 sents the number of gallons to be delivered per hour, (/} the length of the 

 pipe m yards, (h) the head in feet, and (d) the diameter of the pipe in inches. 

 We now obtain the following diameters, first 200 yards 5Jj inches ; second 

 ditto 4^ inches; third ditto SJl^ inches; to which, adding half an inch for 

 possible contraction by corrosion, the practical diameters become six inches, 

 five inches, and four inches for a street producing in London a water rental 

 of at least 300/. 



"What would he the saving in the size of the pipes consequent on the sys- 

 tem of constant supply as compared with the intermittent system ?-The 

 diameters of the service-pipes and sub-mains are diminished about one-third, 

 and the weights of the pipes about one-half. 



" The saving in the size of the service-pipes, the mains, and so forth, would 

 compensate for the cost of throwing up by engines an additional quantiiy of 

 water to meet the apprehended waste and additional consumption, and keep, 

 mg It constantly on?- Yes; and the management is much more easy, and 

 tlie number of men necessary to superintend the distribution of the water be- 

 comes much fewer,-in fact, it demands very little attention indeed, where 

 the water is constantly running through the pipes; but where the water is 

 given at intervals, many persons are put to great inconvenience; then they 

 are complaining, and must be attended to ; and the ball-cocks when they go 

 down will slick very frequently, and there is, consequently, a great waste of 

 water, so that a great quantity of water is not well applied. The waste is 

 very great on the intermittent supply, much more, lam satisfied, than most 

 engineers are aware of. We have found, in many instances, where our sup- 

 ply has been turned off a particular street for a short time, the ball-cock of a 

 cistern has gone down, and the water run to waste after being again turned 

 on. That happens in all towns where the supply is intermittent ; and I be- 

 lieve the waste from this and some other causes is much greater than that 

 which occurs in a constant supply. 



"In stating generally your view that the supply of a town by the medium 

 of a constant supply anil high pressure is quite as cheap or cheaper than 

 under the other system of an intermittent supply, do you take into considera- 

 tion th;.t, in the one case of constant supply and high pressure, there would 

 be greater advantage to the people and a greater supply of water?— I did not 

 take that into consideration in the first instance ; but I think the saving in 

 the number of officers and in other respects would more than compensate" for 

 the cost of pumping that quantity of water ; for the mere cost of raising the 

 water is but a trifling portion of the expenses of a Water Company : a great 

 many expenses are permanent standing expenses ; the greater proportion are 

 in a great degree independent of the quantity of water lifted.— For 4s. id. a 

 house, we give the constant Supply of water which is required for the use of 

 a cottager's family. 



"Under the existing circumstances at the prices charged and the benefit con- 

 ferred, do the Company divide actually five per cent, upon the outlay ?— Yes, 

 and the 50/. shares of the Company sell at from 70/. to 73/. each, and have 

 done so for some years. The dividends of the Company are 3/. on each 50/. 

 share, and that is considered in the transfer of shares to represent a value 

 of 70/. 



"If a city were situate near a very high elevation, on which it would be con- 

 venient to place the reservoir, say 300 feel, giving a greater pressure for the 



tenants' communication pipes in the lower districts than is requisite for the 

 various purposes of constant supply, at high pressure, have you any plan of 



