ON THE TREATMENT AND UTILIZATION OF SEWAGE. 441 



Only vague information was obtained about the ventilation of the sewers, 

 " owing to the fact that very few instances exist in which any thing has been 

 systematically done." The Committee in their First Eeport stated that this 

 was a most important matter for consideration, and " that it would be in the 

 highest degree desirable to institute an inquiry into the nature of the 

 gaseous emanations from the sewers in various places " (Report I. p. 330). 

 They consequently instituted some experiments, both chemical and microsco- 

 pical, on air collected from some sewers in Paddington. Dr. Eussell's analyses 

 showed that the carbonic acid varied from 0-12 to 0-51 per cent., and the 

 oxygen from 20-7 to 20-91 per cent. ; while no combustible gases were detected, 

 and only a trace of ammonia could be discovered in Avater through which a 

 large quantity of sewer air had been passed. The remark is made that 

 " these experiments must be looked upon as simply tentative, but certainly 

 indicate a purer air in these sewers than might have been anticipated." The 

 microscopical examination conducted by Mr. Cooke showed that the suspended 

 substances which were collected by passing air through tubes containing 

 plugs of cotton-wool were very various, and consisted of inorganic matters, 

 a few starch-granules, and spores of various sizes, together with fragments of 

 cellular tissue, woody fibre, fibrils of feathers, &c. The general results, how- 

 ever, indicated " comparative freedom from organic bodies." (Eeport II. 

 pp. 72-75.) 



The Committee made a special investigation into the sewerage arrange- 

 ments of the town of Cambridge, where water-closets are general, though 

 not universal. The outlets of all the sewers were found to be under the 

 level of the surface-water in the Cam, so that " the sewage is backed up in 

 the sewers for a considerable distance ; and the subsoil is constantly saturated 

 with both water and sewage in the lowest parts of the town." As many of 

 the sewers are old and of irregular shape, much escape into the subsoil takes 

 place. " Inquiries were made into the state of some of the wells belonging 

 to private houses, and it was found that they were all contaminated by 

 sewage, owing to their proximity to the sewers in the streets and to the 

 drains on the premises, so much so, that the water cannot be used for drink- 

 ing but only for washing." The remarks made on the subject by the Sub- 

 committee, consisting of Messrs. Grantham (Chairman), Corfield, Hope, and 

 Williamson, finish as follows :— 



" The chief general importance of the inquiry into the conditions of Cam- 

 bridge is the proof thus obtained of the pollution of Avells, and therefore of 

 subsoil, by the agency of previous street- or house-sewers constructed in their 

 vicinity ; and the Subcommittee desires to give expression to the conviction 

 forced upon it in the course of its inquiries, that all sewers, properly so 

 called (that is to say, drains into which refuse from human habitations is 

 admitted), ought to be constructed of materials which are altogether imper- 

 vious, and that a separate system of pervious drains, similar to agricultural 

 drains, shoiild be constructed where necessary to dry the subsoil. The Sub- 

 committee is of opinion that the further construction of pervious sewers 

 should be prohibited by Parliamentary enactment." (Eeport II. p. Gl.) 



The amount of sewage discharged varied in the 200 towns scheduled, partly 

 with the amount of the water-supply, and partly with the amount of surface 

 or subsoil waters admitted into the sewers — the largest quantity being in the 

 case of the town of Hertford, where the discharge per head per diem 

 amounted to 257 gallons, the water-supply being only 61^ gallons ; and tho 

 smallest, amounting to only six gallons per head per diem^ being recorded in 

 one or two instances. 



