MECHANICAL AND USEFUL AKTS. 81 



fifth of a grain of sulphuret of carbon, and one- twentieth of a grain 

 of ammonia, it becomes surprising that the effects, bad as they are, 

 are not more sensibly felt. 2ndly. That the gas-mains and water- 

 mains usually lying side by side, the escaped gas from the former 

 will frequently enter the water mains at their joints ; and at times, 

 when the water but partially fills the pipes, a large quantity of gas 

 in this way gets admitted, and, mingling with the water, imparts to 

 it that nauseous quality so frequently complained of. And hence, 

 too, the cause of the not unfrequent occurrence of partial explosions 

 by the ignition of gas from the presence of a lighted candle on the 

 opening of the water-tap. 3rdly. That the mud banks, the sewage 

 deposits on the tidal banks of the Thames within London, derive 

 their peculiar foetid and blackened character from the action of gas 

 leakage on the oxide of the corroded street mains, which finds its way 

 by numerous channels into the sewers, and is thence carried to the 

 river, where, retained in the sewage mud, it becomes the direct 

 agent of the too well-known noxious odour the Thames water evolves 

 in the summer months of June and July, when the temperature 

 ranges above 70° Fahrenheit. 



The properly constructed accessible subioay, for the " common " 

 conveyance of the mains through at least the greater trunk lines of 

 the metropolis, offers the medium of extensive mitigation of all these 

 evils, since the facility for a system of daily inspection and immediate 

 repair would admit of the maintenance of the mains gas-tight and 

 water-tight, as in ordinary house fittings. — Communication to the 

 Builder. 



SUBWAY IN LONDON. 



The Metropolitan Board of Works have published the plans for a 

 Subway in the new street to Covent-garden (commencing at the 

 junction of Long-acre and St. Martin's-lane), which were prepared 

 for them by Mr. Marrable and Mr. Bazalgette, their architect and 

 engineer. The following report accompanies the drawings : — 



Having been directed by the Committee on New Streets to prepare a design 

 for a subway under the new street leading from Cranbourne-street to Covent- 

 garden, in which the pipes and mains for gas and water might be laid in such a 

 manner that easy access could be had to them at all times without disturbing the 

 surface or roadway, we now beg to submit the accompanying plans, which we 

 believe to embrace all the desiderata of such an arrangement in the simplest 

 form and at the least possible expense. The plan consists chiefly of a central con- 

 tinuous passage or subway, extending the whole length of the new street, of suffi- 

 cient dimensions (12 feet by 6 feet 6 inches) to admit of the deposit of any requi- 

 site number of gas and water mains, with ample working room for alterations, 

 additions, or repairs. Under the centre of this passage runs the sewer, to which 

 means of access by man-holes are provided at convenient distances, as also venti- 

 lating shafts, gullies, &e. Side-arched passages communicating with the central 

 way will be constructed between every two houses, in which the service-pipes 

 will be carried from the mains into the open areas in front of the houses, and 

 open channels will be left in the footings of the walls dividing the house-vaults, 

 through which the service-pipes will be passed, without any interference with 

 the structural arrangement, and these channels, although of small dimensions, 

 (i\ inches by 3 inches), being always left open, will act as drains for the ad- 

 mission of air from the open areas into the central passage, which, in conjunc- 

 tion with ventilating shafts at convenient distances into the roadway, will secure 



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