1819.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL, 



189 



sewers for town drainage. The Metropolitan Commissioners recommend 

 tlie tubular system, varying from G to 24 inches in diameter, Vfith a double 

 line of pipes, and in low districts converging towards a central well, from 

 whence the sewage is to be pumped hy a steam-engine, and forced to an 

 outlet on the banks of the tiver. In the carrying out of this system, it was 

 intended only to have them of the bare minimum capacity required for 

 house drainage, and storm water was to find exit in any way it coulil. 



The Metropolitan Commissioners also condemned the sewerage works of 

 the City of London, and the Corporation in consequence called in Messrs. 

 Walker, Cubitt, and Brunei, the eminent engineers, to examine and report 

 upon them. The report repudiated the idea of reducing the size of the city 

 sewers, generally approved of the system adopted there, and recommended 

 the extension of it to undrained streets and a system of flashing. They 

 further state that London is the best drained city in the world, and that it 

 is in advance of, and has taught all other cities lessons in sewerage. 



Manchester, 1 believe, is the only town that has taken the initiative from 

 the sanitary reports, and generally introduced tubular sewers, which if more 

 efficient than brick construction, are also much more costly, as will appear 

 by the following table : — 



Egg-shaped Brick Sewers of 

 tbe 3:ime ca[)!iciLy. 



2^. 6t1. per yard. 



3s. 1. 



.Is. (Id. " 



Egg-shaped Tubular Sewprs. 

 In. In. Per Yard. 



12 by 1) at 4s. Od. 

 16 '• 12 " Ts. 6d. 



20 " 15 " 10s. ed. 



Od. 

 Si. 

 Ud. 



Tliis is exclusive of excavation iu both cases. 

 An ingenious gentleman, named Wilkinson, of Newcastle, has invented a 

 material for sewers, wljich he states is coniposeil of a cement made in a pe- 

 culiar way, and which will increase in hardness with age ; it possesses 

 advantages over similar articles made of clay, as it does not warp or twist, 

 and the inverts can be made in 12 feet lengths, and tbe smaller size pipes in 

 4 feet lengths, they have also loose covers, so that they can be readily 

 examined at any time. The prices are as follows : — 



2 inches bore 3d. per foot. (J inches bore Ud. per foot. 



3 " 4d. •• 10 " Is. 4d. '■ 



Sewer in Blocks, 4 feet by 2 ft. C in., Ss. per foot. 

 Blocks for Inverts, 2s. per loot lineal. 



The tubular system of sewers as a whole is not generally adapted for 

 towns, it may suit small tovins, or small collateral streets of large ones, but 

 they have not yet been manufactured large enough to be suitahle as main 

 drains for the drainage of large areas. 



The sizes of sewers must depend entirely upon the area to be drained and 

 the fall or declivity to be obtained to the point of discharge, and at the 

 same time, they should be large enough not only for house drainage, rain 

 and stone water, but an allowance should be made for extraordinary storms. 

 It has been the custom with all our eminent liydraulic engineers not to ap- 

 portion their hydraulic or other works to the bare minimum duty they have 

 to perform, but to make due allowance for any unforeseen contingencies. 



This has been strongly confirmed by the report on the City of London 

 above alluded to, in which it is stated that sewers should be large enough 

 to admit a man for the purpose of repair or to remove deposit, and that the 

 size for the main sewers should be 5 feet hy 3 feet, and secondary sizes 

 3 feet by 2 feet. They further state that the air of small sewers is worse 

 than large ones, and that no evil effect can be apprehended from well- 

 constructed brick sewers with a good fall and well cleansed, and they act as 

 under drains for the surrounding earth, which tbe entire substitution of 

 earthenware pipes wlih tight joints, would practically prevent. 



Sewers with an Inclination of 1 In 250 will keep themselves clean, without 

 the aid of flashing; but when the Inclinations exceed that, a system of 

 flashing is indispensable to prevent deposit. But I consider in every case 

 an occasional cleansing of the sewers, where a current of water cannot be 

 obtained to pass through them, beneficial, as It tends to sweeten and purify 

 them, and is the means of removing the causes of noxious exhalations. 



The form of sewer I have adopted is one approximating to tbe egg-shape 

 (tbe true egg-form not having yet been coricctly developed for sewerage 

 purposes), the arch is semi-circular, and the invert a series of segments. It 

 departs as little as possible from the strong and advantageous form of the 

 circle, (which is the figure of greatest capacity with an equal circumference) 

 while from placing the narrow end downwards, it concentrates the flow of 

 the water over a smaller area, reduces the friction, and thereby adds mate- 

 rially to Its capability of discharging fluids. 



It is generally considered that the cylindrical is the strongest form that 

 can be adopted for sewers; but there are other questions to be taken into 

 calculation, as before stated, besides strength, viz., the best shape for the 

 passage and discharge of fluids, and that is now generally admitted to be the 

 egg shape. 



I would strongly recommend for our future operations, the use of the 

 Portland or lias cements for the Inverts of our sewers, and blue lias lime 

 for the arches, as no other material should be used than good hydraulic 

 mortar in structures that are iu any way exposed to the action of water, 

 and where durability is desired. 



The Portland and blue Has cement is cheaper than the Roman cement, 

 as it will bear a greater proportion of sand, while its strength and dura- 

 bility is superior. Puzzolano or T'erras are good hydraulic cements for 

 sewers, though probably more expensive than those above staled. From 

 e.xperimenta recently made, 1 find that smiths' ashes, or black oxide, adds 



very materially to the strength of hydraulic mortar, though it adds also a 

 little to the expense. I think if ariaugements could be made, it wimld be 

 desirable to have the inverts of our sewers manufactured iu blocks, say 

 one foot or more wide, and two or three feet lengths, so as to have as few 

 joints as possible in the invei'ts ; and this might be further improved by 

 having tbe Interior surface glazed. 1 have made Inquiries from various 

 manufacturers, and they state there would be dilficulty in making them. 

 Again, it may be a question whether or not a smoother Invert may be 

 formed by rendering the interior surface of the brickwork over with 

 cement, as Is the practice of some eminent architects. 



The same objection applies to the formation of the inverts of our sewers 

 in tbe rock, as to the dry brickwork alluded to above — the sewage will be 

 certain to percolate through the fissures in the rock. Tiie inverts of 

 sewers should invariably be made impervious to moisture. 



Ventilation of Sewers. — Much of the otl'ensive gas that now escapes from 

 our sewers, might be prevented by trapping the openings elTeciually, and 

 by connecting air-shafts or flues with the sewers, or the walls of the 

 hishest houses on the summit levels, so that the foul air may be sent ia 

 the atmosphere, and dispersed where It could not possibly be injurious or 

 offensive. This is a plau I proposed two years ago, it is very simple ia 

 Us nature, and would, I think, prove effective.* 



In London they are trying experiments to burn the gases by placing fires 

 on gratings over openings in the sewers made for that purpose; from 

 which it is proposed, I believe, to carry large chimney shafts to convey 

 away the smoke and effluvia: but this Is an expensive operation. 



Contracts. — I would again endeavour to impress upon you the impor- 

 tance of conducting our sewage works on a diiferent principle than we 

 have hitherto done. I would recommend the earthwork to be let by con- 

 tract ; the brickwork 1 would execute, and I would employ first-rate 

 workmen, at good wages, for that purpose. The bricks, cement, and 

 niurlar, we should find ourselves; and the whole should be done under 

 competent inspection. 



At the present time it is necessary to have an inspector at the sewers, to 

 see tiiat the brickwork is executed properly by the contractor. This 

 same person could superintend the bricklayer as well as he could the 

 workmen of the contractor, and thereby save the contractor's profit, which 

 amounts to considerably more than his wages would come to; besides, we 

 should have more efllcient work. Mr. Newlaud, the borough engineer of 

 Liverpool, has adopted the plan, and approves of it. He calculates it 

 saves from 25 to 30 per cent. 



Gratings. — It has been a practice with nie to place our sewer gratings 

 about fifty yards asunder ; they are made slightly, dished in the middle, 

 and with bars about | in. apart, so as ell'ectually to prevent stones and 

 other solid substances getting into the sewer : the bars are also beveled on 

 the under side, so as to prevent the dirt clogging to them. They measure 

 IG in. by 13^ in., and are about 2 cwt. each, and ne connect,tbeni with the 

 sewer with 9-in. pipes. Tbe old gratings weighed about 5 cwt, and 

 measured 30 in. by 24 In., with b.irs Ij In. to 2 iu. asunder. I often found 

 them connected with the sewer by 9 la. drain pipes, of an area of 03 in., 

 while the clear area or space between the bars was about 351 inches. 

 The old traps also were of similar huge dimensions as to area. 



I have recently introduced side gratings fitted into the curb stones, which 

 are more eliiclent, and not so unsightly as the old gratings; these, I find, 

 are recently introduced into Liverpool, and they have for many years been 

 adopted iu Birmingham and Paris. 



In London, Liverpool, and other towns glazed pipes only are allowed 

 to be used, and in the former places they are uow entering into large con- 

 tracts fur supplies of them. Glass pipes are now being manufactured lor 

 the purposes of drainage and as water mains; from their straightness and 

 extreme smoothness, they will discharge a greater amount of fluid than 

 glazed pipes, but their high price, which is as follows, is rather an obsta- 

 cle to their nse. 



1 inch 7d. per foot. Ji inch 141. per foot. 



IJ •' 8d. " 24 " VA. 



U " 9J. " 2i " Ifd. " 



Ij " Hid. " 3 " 2Ud. " 



2 " 12J. 



The ends of the pipes are now annealed, so they are not so liable to 

 fracture as when first made, and tbe manufacturers have invented a collar 

 and cement that is used for the purpose of joining them together, and 

 which makes a perfectly water-tight Joint. 



As the best security against the passage of foul air from sewers and 

 drains, all openings should be trapped, and the most etfectual trap I con- 

 sider yet invented for house drains is the syphon trap of glazed stone 

 ware. I have recently introduced the patent valve trap, the pipe being 

 composed of glazed sluue ware, and the valve of galvanized iron, but I 

 have discovered that it is not so effectual as the syphon trap, as you cannot 

 ensure tightness at all times, but they eflfectually prevent vermin getting 

 up the drains. 



Street Cleansing. — The thorough cleansing of the streets of towns has a 

 salutary effect on the health of the inhabitants. Our principal thorough- 

 fares should be swept daily, and the Inferior streets twice or thrice a week, 

 and at the same time the streets are swept, the courts should be cleansed 

 likewise. Our principal streets contain 22,202 superficial yards ; second 



* Tliis system ol ventilation is vicious in princple; by it the air w« breathe would liecome 

 contaminated. By the action of Ihe wmd, the upper stratum of air becomes iatermingted 

 with the lower stratum.— £d. C.E, & A. Journal. 



