484 Town Sewage. 



After a careful consideration of all the circumstances and 

 details, it appears that the following practical conclusions may 

 safely be deduced from these experiments : — 



1. That by the use of sewag-e a very great increase (varying 

 from two to three fold according to the season), may be obtained 

 in food, milk, or value of the milk. 



2. That a yet larger increase may be anticipated from the 

 application of sewage systematically over large tracts of average 

 or sandy land, than was obtained from these pastures of natu- 

 rally good feeding quality, and consequent high natural yield. 



It is estimated that with 5000 tons of sewage judiciously 

 applied to Italian rye-grass or meadow-land properly laid down 

 to receive it, an average gross produce of not less, and perhaps 

 more, than 1000 gallons of milk per acre per annum might be 

 anticipated, Avhich, at ^d. per gallon, would represent a gross 

 money return of 33Z. 65. 8f?. 



Or, to put the result in another way, it required, according to 

 circumstances, the consumption of between 5 or 6 tons of grass 

 for the production of 1 ton of milk ; and if we reckon 6 parts 

 of grass for 1 of milk, and 30 tons of grass per acre, this would 

 give a gross return in value of milk at ^d. per gallon, of some- 

 thing over 37Z. per acre, or of about 25^. per ton, of grass 

 consumed. 



Composition of the Drainage Water from Sewage Fields. 



But a further question arises : — would the sewage be suffi- 

 ciently purified by such an application as 5000 tons per acre ? 



To determine this point samples of the drainage water were 

 collected for analysis in each field simultaneously with those of 

 the sewage, commencing in May, 1862, and ending in October, 

 1863. In all sixty-two partial analyses were thus made, to 

 which a few others, much more detailed, were added in 1864. 



The result of the sixty-two analyses are summarised in 

 Table VIII. (See following page.) 



It is seen that of matter in suspension in the sewage, nearly 

 the whole, inorganic or organic, was retained by the soil, and 

 of the little which the drainage-water contained, probably a con- 

 siderable part was derived from the soil itself. 



Of matter in solution, on the other hand, the drainage-water 

 contained much about the same amount, inorganic and organic, 

 as the sewage ; though doubtless it had derived much of this 

 also from the soil, the sewage giving up valuable fertilisers to 

 the soil, and the fluid in its turn taking up substances from it. 



and tbe amount oi milk, "esclusiye of oilcake," by deducting from the gross an:o.int of milk with 

 oilcake at the rate of one gallon for every id. of deductad value. Such estimates are, however, 

 obviously only approximations to the truth. 



