14 SEWAGE AND ITS PURIFICATION 



and the contents were emptied on the beach at irregular 

 intervals. " In other instances people ordinarily use the beach, 

 or, in the event of the tide being up or the weather bad, any 

 other spot convenient. At the shipbuilding yards there are 

 wooden privies built out upon the quay, and used by the work- 

 men employed in the yards. The excrement in these cases 

 drops into the water at high tide, but on the beach at low 

 water." 



The infection that is disseminated by flies from collections 

 of faecal matter has been proved in South Africa and in India, 

 and also by Dr. Martin in England.^ 



Majors Firth and Horrocks^ say that "Our investigations 

 as to the vitality of the enteric bacillus in fsecally-fouled soils, 

 whether wet or dry, demonstrate the risks attending the earth 

 or pail closet system of excretal removal." They explain how 

 these portable middens may be, and often are, foci of enteric 

 infection, and conclude that any installations of the kind in 

 towns and large communities are most objectionable. 



At Leicester an inclusive estimate of costs gave a preference 

 to water-carriage over the pail system in the ratio of 8s. 6Jd. to 

 9s. 5d. per closet per annum.^ 



Effects of Dilution. 



With conditions that are favourable, the purifying action of 

 rivers is known to be very great. Towns on the banks of rivers 

 of considerable width, and having a fairly constant volume and 

 velocity during all seasons, have discharged their raw sewage 

 into the stream for many years, and investigation has proved 

 that a few miles below the outlet of the sewers there is little or 

 no trace of pollution. Any improvement by mere sedimenta- 

 tion would be on wrong lines, and should not be permitted, as 

 it would result in filling up the river bed and formation of foul 

 dirt banks (p. 4), although the increase in volume of mud-flats 

 in estuaries cannot be attributed to sewage except in isolated 

 and local cases. The amount of solids present in the sewage, 



1 See Aldridge, " Enteric in India," Journal of Hygiene, July, 1902, p. 367 ; 

 also A. W. Martin, Public Health, August, 1905, p. 709. 



■^ "Viability of the Enteric Bacillus in Soil and Sewage," Journal of the 

 Sanitary Institute, vol. xxiii., part iv., p. 615, 1^03. 



^ " Collection, Disposal, and Utilization of Town Refuse in Leicester," by 

 F. W. Allen, Assistant Borough Surveyor. Journal of the Sanitary Institute, 

 vol. xxvc, April, 1904. 



