ON THE TREATMENT AND UTILIZATION OF SEWAGE. 69 



square holes cut out in their centre of different sizes. It will thus be seen 

 that the methods in which the experiments were conducted gave three di- 

 stinct and separate sets of data on which to base calculations ; and it resulted 

 that land in the state of moisture which existed on the 19th March and laid 

 out in beds of 30 feet wide wovdd only absorb, when consolidated, on the 

 surface about 40 tons of liquid per acre, and when stirred to a depth of 9 

 inches on the previous day, about 90 to 110 tons per acre. By the word 

 absorb is meant that no more than the above quantities could be applied 

 without the formation of puddles at the sides of the beds. Of course, to lay 

 down dogmatically that land under any given condition wiU absorb any exact 

 number of gallons, or even tons, to the acre would be mere pedantry, and 

 therefore it was sought in these experiments to ascertain what might be con- 

 sidered, after several different trials, to be the average figures. The ques- 

 tions what are the minimum and maximum quantities that can be absorbed 

 by land abnormally saturated by heavy rains in winter when there is little 

 evaporation, or abnormally dried by repeated agricultural operations per- 

 formed in a period of drought, when there is a maximum of evaporation, have 

 not been yet ascertained; but the state of the land on the 19th March may 

 fairly be taken as an average condition : and this, after aU, is more important 

 than the observation of occasional extremes ; and the box-experiments about 

 to be conducted wiU afford an opportunity of making these further observa- 

 tions with far greater accuracy than could be attained on a larger scale. 



If we divide the average daily quantity of sewage and effluent water (namely, 

 about 1400 tons) pumped on to the farm during the period observed, and 

 during which period the land was, as a rule, well stii'red, by the figure of 

 100 tons, arrived at by the experiments conducted on the 19th March, we 

 get 14 acres as the quantity irrigated every day; but this would not be cor- 

 rect, because there were at work the disturbing causes of the excessive 

 drought and the artificial amount of evaporation induced by the great number 

 of manipulations which the larger part of the farm had received in the process 

 of laying out the ground ; and, as a matter of fact, the average area irrigated 

 daily from the 18th May to the Ist September has been a little over 5^ 

 acres. Then 0-34 being the point of saturation of those samples of the soil 

 chemically examined and analyzed, it would foUow that if we assume that 

 the liquid would not penetrate during the few minutes employed ia dressing 

 the surface at any one part of the bed to a depth of more than 10 inches 

 (although the land was cultivated to a depth of 20 inches), the maximum 

 quantity of sewage that could be applied, supposing the soil to be not only 

 abnormally, but even chemically dxy, would be 384 tons per acre. In all 

 probability, therefore, 400 tons per acre is the largest quantity that has ever 

 been applied in any one dressing ; and if we assume that the first dressing 

 all over was at the rate of 400 tons per acre, that the second dressing was at 

 the rate of 200, and that the subsequent dressings were at the rate of 100, 

 we shall not be far from the truth. 



Although, as has been explained, nothing in the way of a complete result, 

 whether financial or chemical, can be obtained from the incomplete observa- 

 tions on the farm, it is not without interest to compare the results of some 

 of the crops with others of the same kind grown in precisely the same soU., 

 on the same tableland, and within a few hundred yards. 



A small field of between 3 and 4 acres in the adjoining farm was sown with 

 peas for picking green. These the farmer tried to sell on the ground for ^8 

 an acre ; but he was unable to sell them at aU, and at last left them to ripen. 

 They still remain unsold, and are estimated to be worth from ^£5 to £6 an 



