472 



Toicn Sewage. 



Table I. — Grains of Ammonia per Gallon in different samples of Metro- 

 politan Sewage, and estimated Value of Constituents in 1 Ton. 



The sample analysed by Messrs. Hofmann and Witt was a 

 mixture of equal portions, taken every hour during twenty-four 

 hours of dry weather, and there is no doubt that that sample had 

 better claim to represent the average dry-weather sewage of the 

 metropolis, than any other that had up to that time been collected 

 and examined. 



The variations in the composition of sewage are even more 

 strikingly illustrated by the results obtained at Rugby, by the 

 Royal Commission, from samples collected under the direction 

 of Messrs. Lawes and Gilbert, and analysed in the laboratory of 

 Mr. Way. 



The samples were thus collected : — About a quart was taken 

 from a gauge-tank holding 3 or 4 tons, at intervals of about two 

 hours, for several days together ; the quantity so accumulated 

 was well mixed, and a sample of the mixture taken : ninety-three 

 such mixed samples were analysed, the period of collecting ex- 

 tending over thirty months, from April, 1861, to October, 1863, 

 inclusive. 



