468 Dr. Lankester, on the [Feb. 5, 



was recommended by the Government Commissioners, on account 

 of its " health, comfort, and economy." 



2. Sulphate of Lime existed in the proportion of from 1 to 

 15 grains in the gallon. It decomposes in contact with organic 

 matters, and produces sulphuretted hydrogen. Very small quantities 

 of organic matter serve to produce this effect. 



3. Chloride of Sodium existed in Thames water, in from 1 to 

 4 grains in the gallon ; in deep wells, from 10 to 17 grains ; and 

 in surface wells, from 20 to 40 grains. In the Thames it might be 

 the produce of the tide, in the deep wells it was washed out of the 

 chalk ; but in the surface wells, where it was most abundant, there 

 could be little doubt that it was derived from the animal and 

 vegetable refuse of the houses through which it percolated. The 

 analyses of above one hundred of these wells showed that they 

 were all equally open to suspicion on this point. 



4. Phosphates and Silica existed in all the London waters, in 

 small quantities. 



5. Ammonia also had been detected in small quantities in the 

 Thames, in much larger and more appreciable quantities in the 

 surface wells. This substance was the result of the decomposition 

 of animal matter ; and in the surface wells was undoubtedly de- 

 rived from human excretions. 



6. Nitrates resulted from the oxidation of the ammonia. They 

 were absent in deep wells ; existed only in very small quantities in 

 the Thames, but in large and sometimes even dangerous quantities 

 in surface wells. In one water, examined by Mr. Noad, above 

 50 grains in the gallon were detected. 



The organic matters were not injurious when fresh or recent, 

 but they assumed certain conditions of decomposition, which occa- 

 sionally rendered them deadly. Their influence might be estimated 

 by the case of the Lambeth and Yauxhall Yfater Company's 

 supply, during the years 1848 and 1854, — two years in which 

 cholera visited London. In 1848, both companies derived their 

 supply of water from the Thames, at Battersea, and both supplied 

 the same district with water, and the houses supplied were equally 

 visited with cholera. But in 1854, the Lambeth Company ob- 

 tained an improved supply high up the Thames, at Ditton. The 

 consequence was, according to Dr. Snow's calculations, that the 

 deaths amongst the population supplied by the Vauxhall Company, 

 as compared with the Lambeth, was as 7 to 1 ; according to the 

 most favourable view of the case, as given by Mr. Swain, it was 

 3^ to 1. There was nothing to account for this difference but the 

 larger quantity of organic impurity in the water supplied by 

 the Vauxhall Company, which still obtained* water from the more 

 impure source. The outbreak of cholera in the Golden Square 

 district, in September 1854, was traced to the pump in Broad 

 Street, which was subsequently found to have communicated 

 with the drain of a neighbouring house. Other cases of disease 



