1869.] The Future Water-sujjphj of London. 227 



may be asked whether, supposhig the water of a river can be kept 

 free from the contamination of all sewage except that which has 

 been filtered through meadow land, it will be safe to use it for 

 drinking purposes ? An absolute answer cannot as yet be given to 

 this question ; but considering the large amount of organic matter 

 which often remains in solution in such fillered sewage,* and the 

 extreme risk of the filtration being in some cases imperfectly efi'ected, 

 it is highly improbable that water so contaminated could ever be 

 used with safety. For the sake of the rivers, and for the sake of the 

 land, the sewage must be purified ; but it should not be forgotten 

 that, after all its purification, it will still be sewage — the diluted 

 and somewhat modified excreta of human beings — and as such will be 

 disgusting, and possibly dangerous, as an article of food. Whether 

 pui'ified or not, the sewage, it is evident, must in most instances be 

 discharged into the nearest river ; and we are therefore led by this 

 view of the case to the general inference that rivers, below the 

 highest points at which they receive sewage, are unfit soiu'ces of 

 water-supply. 



But the subject of the sewage-contamination of water cannot be 

 dismissed quite so easily as this. Very contrary opinions are held 

 in regard to it ; for although no one doubts that water largely con- 

 taminated with recent sewage is likely, or, rather, almost certain to 

 lead to epidemic disease, many persons beheve that, provided the 

 admixture be small and that it has flowed for some miles down the 

 stream, the well-known self-purifying power of the water, due to 

 its dissolved oxygen, will have destroyed all organic bodies in it, 

 and have rendered the sewage perfectly innocuous. This is the 

 view held, very naturally, by the London water companies, and 

 strenuously supported by Dr. Letheby, their consistent and zealous 

 advocate. The question has been chiefly argued in relation to the 

 cholera, and it will therefore be convenient to keep to that issue, 

 although it must not be forgotten that sewage-polluted water is 

 quite as deeply implicated as a cause of other forms of epidemic 

 disease. Let any one who doubts this read the ' Keport on Typhoid 

 Fever at Tottenham,' by Dr. Seaton, and at Buglawton, by Dr. 

 Buchanan. Both are printed in the Appendix to the Ninth vReport 

 of Mr. Simon, the medical ofiicer of the Privy Council, 1867. 



This last-named Keport, together with the excellent ' Eeport on 

 the Cholera Epidemic of 1866,' by Dr. Farr,t which forms the 

 supplement to the Twenty-ninth Annual Keport of the Kegistrar- 

 General, afford ample materials for a consideration of this question, 

 a consideration which is forced upon us by its close and intimate con- 

 nection with our immediate subject. It is unnecessary to multiply 

 proofs that water contaminated with choleraic discharges is a frequent 



* ' Third Report of the Sewage Coramissiou, 1865,' p 4G. 

 t Published 1868. 



