314 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



have adopted the oval sewer, and decreased the quantity of material. When 

 tlie walls were uprifiht, it was necessary to give an increased thickness tu 

 them tu obtain the requisite strength ; but by making that curve on the sides, 

 the shape being an arch to a certain extent, renilcrs that thickness unneces- 

 sary ; it resists the pressure from without. The difference of cost of those 

 two sewers is 3s. a foot in the larger size ; in the other, or second size, ihe 

 cost remains about the same, as it had only a 9-inch wall before. There are 

 many cross streets in the district where there are but few houses to drain, 

 where, if a long length of sewer was built, it would become very expensive lo 

 those few houses. Curved -formed sewers, he considered, would enable tlie 

 commissioners lo afford a sewer for those cross streets of a much cheaper 

 description, and he suggested that tliey should adopt a sewer half brick in 

 thickness, built of blocks of brickwork and cement all round, and that that 

 would be sufficiently strong, if made with radiated bricks, wiih blocks in (c- 

 ment. That suggestion the commissioners have adopted, and that enables 

 them to afl'urd the public a saving of 5.5. a foot run upon the tecond-sized 

 sewers. They have the same capacity as the seconil-sized se«ers. 



" What was the difference of the expense between using the radiated bricks 

 and the common slock bricks in the construction of sewers ? The brickmaker 

 charged 8s. a thousand more for the radiated stock than the common slock ; 

 the common stock is 32*. ; he charges 2/. for llie radiated bricks ; but if there 

 was a competition for radiated bricks, Ihey would cost very little more than 

 the common brick. — What is the diflcrence in the expense in building a scivcr 

 with the radiated brick as compared with the common brick ? The difference 

 consists in Ihe radiated brick being used with less materials, as they fill up 

 the space which would otherwise be occupied by cement ; therefore in reality 

 there is no extra cost, for it saves so much cement. There is also less work 

 in putting them in, while if a man has to use mortar, he has not to take up 

 so much mortar or cement as with the common brick. — Would it not be de- 

 sirable, if you could, lo have a block burnt, so as to have ready to yourliands 

 sucli blocks as you wanted, of two or three diHerent sizes? I believe it 

 would. A brickmaker « ho called at the office, and saw this form of sewer, 

 considered he could burn bricks which would suit us better, and enable us to 

 do the work at less expense. The inverts of the first and second sized sewers 

 are put in with blocks, formed in wooden moulds with cement. Class (C) in 

 Ihe diagram, which is the smallest sewer, is formed huIi less material in 

 moulds with cement. — Put in with joints? Yes, the whole round of the 

 sewer takes those moulds. — You used very little cement with the old sewers- 

 None at all ; we now use it in the bottom, and we have found it to answer a 

 very good purpose, for in bad bottoms in running sand they could no work 

 in without blocks. We have sewers uf all classes in it now. — To what height 

 do you carry this cement ; is it to the average height that the water runs in 

 those sewers? To the common run of 'the water, generally, in the main 

 sewers. The cemented invert is composed of three blocks, one in the centre 

 and one on each side." 



"The river Fleet is now arched over for some miles (ivith the exception of 

 the portion in Clerkenwell, the execution of which is waiting for the opening 

 of the new street) ; this arching has been done by the commissioners appro- 

 priating 1,000?. a-year f(jr it; last year and this year it was carried up to 

 Kentish Town beyond Ihe .Seven .Sisters road ; within the last three years 

 14,000/. has been expended upon the river Fleet i since 1826, altogether 

 38,000?. — " Is it necessary, in the construction of sewers in your district, to siru' 

 or prop the sewers in the progress of building them ? The earth is all strutted' 

 not the sewer. — Have you any quicksands to go through which require ex- 

 traordinary precaution ? Cases might arise where the sewc would re(|uire to 

 be strutted in.side during its execution; we have gone tlirough very bad 

 ground, and have built a new sewer on the side of a hill ; but in those cases 

 we have not found it necessary. — How do you describe the curves of the sides ? 

 We have a template for the men to work to. — What description of ground do 

 you contemplate ever to be necessary to require the strutting of the inside of 

 tlie sewer? I should say in a very rainy season, through slippery clayey 

 ground : I do not consider that we should require to strut the curved form of 

 sewer in any ground, as we have used it in tunnelling in very bad ground ; 

 in River-lane we tunnelled a second sized sewer at tlie depth of 38 feet. We 

 passed under Ihe New Kiver and met a ground in w liich the men sank up to 

 their knees for 100 feet in length, where we had to put in a foundation ; still 

 we made the sewer with safely, and it stands. — Do you use any special pre- 

 cautious, where you tunnel through a quicksand such as you have described? 

 Yes; instead of open timbering, we secure it with close timbering." 



" At what distance from the point where you have been working have you 

 known houses aft'ected.' I have known houses affected for 1500 feet from 

 the side of the sewer at Pentonville. A sewer was built before I came to 

 the commission towards North-street, and it had the effect of loosening the 

 ground, or causing the ground to slip the whole way up the hill ; it may be 

 seen to this day in the garden walls, which have not been repaired. — .\ie 

 you troubled with the rising of the sand ? Yes.' — Do you use means to pre- 

 vent that? We have no occasion to do that, since we used blocks; they 

 answer for every purpose. — What is the greatest height to which you have 

 known sand rise in a night ? Not more than five or six inches in a night. 

 The slip of 1500 feet was on the side of a hill, not ou flat ground. The first 



sized sewer is evidently formed for the purpose of meeting the case of an in- 

 creased quantity of water passing down. The commissioners of the Holborn 

 and Finsbury division have been very careful in that respect. In the course 

 of the river Fleet, it was thought necessary to build a sewer 12 feet high and 

 12 feet in width on the Caltborpe estate. Afterwards the conimissinuers, 

 having another portion to build, referred it to their officers to suggest what 

 size would suit : the portion of the sewer next built was belnw that. The 

 reports of the officers certified tliat a sewer of 10 feet in width and 9 feet 

 high would be sullicieut, from an advantage in the difference in the fall, there 

 being more fall in this situation, which rendered the proportion of the cur- 

 rent through the smaller sewer equal to the larger one. — What was the area 

 of the larger sewer? The area was 12 feet by 12, with a circular arch of 

 six feet radius ; the upright side walls four feet ; and the rest was occupied 

 by the invert. The river Fleet takes the water from llighgate and Ilarap- 

 stead, and I have known it rise six, eight, and ten feet in a night ; there 

 have been instances of persons being carried away by it. It is in my recol- 

 lection that at Battle Bridge the water has been six or eight feet deep, and 

 persons were carried about in boats." 



Mr. Dowley, Surveyor of the Westminster Commission — " Do you use ce- 

 ment in the construction of your sewers ? We do in some parts. — Where 

 do you use that ? The three centre courses of every invert are built in ce- 

 ment. — What lime do you use for the rest ? Dorking lime." 



Mr. Kelsey, Surveyor of the City Commission — " Our main sewers are very 

 large. The London Bridge sewer is 10 feet hyS feet, and that is ova! at its 

 coramencemeni, and it terminates at Moorgate-street 8 feet 3 inches by 6 feet 

 9 inches. The reasons which induced me tu adopt that size are contained in 

 the following statement : — 



" Tlie Bishopsgate-street sewer, which receives the waters of Shoreditch 

 and adjacent places, being 5 feet by 3 feet, and opening into the Irongate 

 sewer, which averages 8 feet by 3 feet 8 inches, is at times overcharged, and 

 pours back the upland waters. 



" The sewer in Walbrook and Dowgale Hill, which received waters from the 

 Finsbury division, was built 5 feet by 3 feet. It was destroyed in 1821, and 

 the houses endangered by continual overcharges from the upland districts. 



The ancient Walbrook, which, at the most, drained the land south of Is. 

 lington and Ball's Pond, &c., must have been much more capacious than the 

 present Fleet sewer. 



The Fleet sewer, which drains the hollow land south-westward of High- 

 gate, is 18 feet 6 inches by 12 feet at the mouth, and 12 feet 3 inches by 

 11 feet 7i inches at the city boundary. This has often been surcharged; 

 and only within the last year, the culvert, so ably constructed at its mouth 

 by Jlr. James Walker, was severely injured by the flood consequent upon a 

 thunder-storm. 



The sewer from Moorfields to Holloway appears to measure upon the map 

 about three lineal miles. In process of time, and as buildings increase, it 

 may throw out branches in all directions, and the three miles may become 

 thirty. Not only all the atmospheric waters which may, upon an average, 

 fall within the valley south-eastward of llighgate (or at least a large portion 

 of them), but all the artificial supplies which the wants of its yet future in- 

 habitants, as well as of those intermediate between Islington and Moorfields, 

 may require will have to be carried off by the city sewers. 



In anticipation of this, and knowing the disadvantages attendant upon 

 sewers of too small capacity, not only has this large sewer been provided, 

 but it has been kept 18 inches deeper than the Wilson-street sewer, so that 

 that may be hereafter deepened should circumstances require it ; and prepa- 

 ration has also been made for the reception of an auxiliary sewer, of equal 

 depth, at the city boundary by Finsbury. place. 



Undertanding by the term ' data' ascertained facts upon which to raise a 

 calculation, there are none ; hut I think there are sufiicient results of expe- 

 rience to justify the precaution taken by me. 



As some proof that I am not aftogether without justification, I beg to ob- 

 serve that, since the work was begun, Mr. Roe has informed me that the 

 water has risen in one of the shafts in Wilson-street 7 feet above the crown 

 of the sewer, although the Eldon-street sewer is 5 feet by 3 feet 2 inches, the 

 London Wall sewer 6 feet by 4 feet, and the main trunk increases from 8 

 feet 3 inches by 6 feet 9 inches to 10 feet by 8 feet at its mouth. 



Fall of Seweks. 

 Professor Hosking — " Have you turned your mind to the practicability of 

 improving the healthiness of inconveniently low situations in or near London ; 

 such, for instance, as that part of Westminster between TothiU-street and the 

 Horseferry-road ! I have ; and I believe that the soil drainage of that dis- 

 trict may be made perfectly efficient, and a very proper and satisfactory back- 

 water obtained from the river to scour its sewage into the river. The tide 

 rises and falls in the Thames at Loudon, at ordinary spring tides, about IS 

 feet, and at neap tides about 14 feet. Now if the outfall of a common sewer 

 be about three feet above low water of neap tides, it will be high enough to 

 allow the escape of everything tliat can have to |iass through the sewer. I 

 have found from experience that sewers, moderately well supplied with back- 

 water, may be made with much less fall than is generally considered neces- 

 sary, and less than this Bill requires. 1 myself directed the diversion of one 

 of the large sewers at the western extremity of London, the Counters Creek 

 Sewer, for a mile and a half of its length ; and for the purpose of obtaining 

 deeper drainage at the upper end, I prevailed upon the Commissioners to 

 allow the fall to be at the slight rate of 1C3 inch — less than If inch— in 

 100 feet throughout the diverted length, the scwcv being the course of a 



