Introductory. 



" (V.) Whether surface irrigation or filtration was 

 adopted. 



" (VI.) Whether the sewage was a domestic sew- 

 age or a mixed sewage. (If the latter, the nature 

 and amount of trade refuse gaining access to the 

 sewers.) 



" (VII.) The provisions made for ' treating ' storm 

 water on the land, and its bulk in relation to the 

 dry-weather flow of sewage. 



" (VIII.) The amount of subsoil water gaining 

 access to the sewerage system, and also the pro- 

 portion of subsoil water which reached the efflu- 

 ent drains on the sewage farm. 



" (IX.) The number of years during which the 

 farm had been in existence. 



" (X.) Whether the whole of the soil was really 

 in active operation, or whether any portion of the 

 sewage escaped, in a practically unaltered condi- 

 tion, through cracks or borings into the drains. 



" (XI.) Whether the different effluents met and 

 mixed together on the farm and discharged into 

 a common channel or escaped separately into a 

 watercourse. 



" (XII.) Whether the effluents were being dis- 

 charged into a drinking water or into a non-drink- 

 ing water stream. 



" (XIII.) Other points to be considered were : 

 Whether the soil was fresh or showed signs of being 

 overdone; whether the farm was well managed 

 and supervised; whether it was worked mainly 

 with a view to producing a good effluent, or to 

 obtaining a profit from the crops; and whether 

 the sludge was disposed of on the land of the 

 farm, and, if so, how and with what results. 



" (XIV.) Further, notes were made with regard 

 to the situation of the farm, the total acreage, 

 the total irrigable area, the average area irrigated 

 at one time, the population draining to the farm, 

 the population per acre irrigated, the number of 

 gallons of sewage per head per day, the dry-weather 

 flow of sewage per twenty-four hours, the number 

 of gallons of sewage treated per acre per twenty- 

 four hours, separate or combined system, cost of 

 treatment, &c. 



" The results of our inspection of twenty - nine 

 sewage farms, when considered in relation to the 

 above factors and their manifold and complex com- 

 binations, led us to conclude that it would be best 



to attack the subject in a broad and general way.* 

 With this object in view, we in the first place 

 limited our observations to the treatment on land 

 either of domestic sewage or of sewage containing 

 no excessive amount of trade effluents. Secondly, 

 we differentiated farms according to the nature of 

 their soils. Thirdly, we confined our investigation 

 of the different kinds of soil to seven varieties 

 fairly representative of those found on different 

 sewage farms, and in use, or likely to be used, 

 for the purification of sewage — namely, sand, sand 

 and gravel, light loam, heavy loam, clay, peat, and 

 chalk. 



" Lastly, we chose for detailed observation sewage 

 farms representative of the above kinds of soil — 

 namely, Aldershot Camp (sand), Croydon (Bed- 

 dington) (gravelly loam), Nottingham and Cam- 

 bridge (light loam), Rugby (High-Level Farm) 

 (heavy loam) [since found to be clay]. South Nor- 

 wood and Leicester (clay), and Altrincham (peaty 

 soil and sand). Luton, a typical instance of a 

 chalk sewage farm, was also kept to some extent 

 under observation. We also obtained some samples 

 from the sewage farms of Worsley (partly peat, 

 partly sand and gravel), Hemsworth (clayey soil), 

 Derby County Asylum (stiff soil overlying red clay), 

 Lindfield (clayey soil), Sandhurst (sandy soil), and 

 Woking (Bagshot sand)." (Part I., pages 5 and 6.) 



Tarms Employed- 

 Change of. 



" It will be noted that the 

 terms ' filtration ' and ' surface 

 irrigation ' are used in place of 

 the older terms ' intermittent downward filtration ' 

 and 'broad irrigation.' The reasons for so doing 

 may be briefly given as follows: In the first place 

 ' intermittency ' is essential whether ' surface irri- 

 gation ' or ' filtration ' is employed, so that if the 

 term ' intermittent ' is to be retained, it should 

 be used alike for the two different methods of 

 treatment. But we think it better to employ it 

 in neither case. Further, the term ' downward ' 

 would seem to be superfluous in connection with 

 land treatment, and, if stress is laid on this term, 

 an impression is apt to be created that a similar 

 action never takes place where surface irrigation 



* " It may be pointed out here that many of the factors about to be 

 dealt with are incapable of beinf;^ weighed or measured as regards their 

 bearing on the subject as a whole. This being the case, it may be said 

 at the outset that the subsequeut interpretation of our facts, in their 

 relation to these variable circumstances, cannot be expected to be other 

 than of the nature of a broad generaUsation." 



