Town Seicage. 



473 



Table II. — Showing the Hip;hcst, Lowest, and Average Amounts of 

 Ammonia, and Total Solid Matter, in Mixed Samples of Kughy Sewage at 

 different times. 



Grains 



per 

 Gallon. 



lbs. 



per 1000 



Tons. 



Total SoUd Matter. 



per 



Gallon. 



lbs.« 



per 1000 



Tons. 



From Apr. to 

 Oct., 1861 ..] 



From Nov. to 

 Oct., 1862 .. j 



From Nov. to 

 Oct., 1863 .. 



Highest 



Lowest 



Mean of 24 analyses 



Highest 



Lowest 



Mean of 34 analyses 



Highest 



Lowest 



Mean of 35 analyses 



15-64 

 2-99 

 6-39 



11-38 

 2-55 

 5-95 



12-81 

 3-14 



7-08 



500-5 



95-7 



204-5 



364-2 



Sl-6 



190-4 



409-9 

 100-5 

 226-5 



216' 

 37' 

 75' 



129' 



50' 

 80' 



269' 



62' 



103' 



6928 

 1203 

 2405 



4138 

 1616 

 2570 



8637 

 1989 

 3302 



According- to our estimate, the value of the total constituents 

 in 1 ton of sewage varied, from about ^d. to nearly 4^. 



Notwithstanding the very great differences here exhibited, it 

 is still believed that the mean of so many determinations indicates 

 approximately the average composition of the Rugby sewage 

 during the period. The difference in the average concentration 

 of the sewage of the different seasons is perfectly consistent 

 with the character of the seasons themselves. Thus the season 

 of 1861-2 was much the wettest; that of 1862-3 was much the 

 driest, indeed extremely dry ; that of 1861 being intermediate 

 in this respect, as well as in the strength of its sewage. 



The mean of the 93 analyses showed about 6^ grains of 

 ammonia per gallon, indicating a total value of about l^d. per 

 ton : but these samples had not been collected at exactly equal 

 intervals ; to correct any error which might hence arise, the 

 mean of each of the 31 months was first taken, and then the 

 mean of the 31 means so obtained; this adjustment indicated 

 about 7 instead of 6|^ grains per gallon. The average results of 

 the 93 analyses further showed that the sewage contained about 

 87^ grains per gallon of total solid matter, of which about 

 two-thirds was inorganic ; and one-third organic. About half of 

 the total solid matter was in suspension, and half in solution : 

 of the half in suspension about four-sevenths was inorganic 

 and three-sevenths organic, and of the half in solution, about 

 four-fifths inorganic, and one-fifth organic. Lastly, of the 

 nitrogen reckoned as ammonia, about one-fourth was in suspen- 

 sion, and three-fourths in solution. 



From all the information at command as to the population 

 contributing to the sewers, the water-supply, the rainfall, and 

 the drainage area, it was concluded that, on the average, there 



