400 
Sewage-Far m ing. 
a cubic yard of Barking soil, the ammonia in the effluent water 
continuously increased, until at the end of three months it rapidly 
approached in quality unchanged and unpurified sewage. 
Beddington soil, on the other hand, submitted to a similar test 
(and in this case taken from a field which had been continuously 
irrigated with sewage for five years), proved such an admirable 
natural filter, that at the end of the same period, the organic 
impurity in the effluent water had not increased. The various 
experiments of the Commissioners upon different soils are de- 
serving of serious attention. They will be found in their first 
Report, pp. 65 to 69. They seem to show that almost any 
variety of porous and finely divided soil will efficiently purify 
sewage to a much greater extent than any farmer could possibly 
require, and that its cleansing capacity depends upon porosity 
and comminution far more than upon its chemical composition j 
also that soils possessing extreme nitrifying properties are far less 
valuable for cultivation than those in which that process is 
carried out with difficulty, or not at all. Experience, however, 
has now proved that almost any light or medium soils will repay 
for the application of sewage, though not all to the same extent. 
These points should not therefore be overlooked by the practical 
man. Asa rule, common-sense and the application of principles 
which govern the judgment in the choice of land for ordinary 
purposes, will suffice for that intended for sewage-irrigation ; 
though, if the Commissioners' experiments are to be considered 
final, science should aid in the selection of land intended foir 
this object. 
Preparation of Land for Sewage-Irrigation. 
The preparation of the land for sewage-irrigation next demands 
attention, and here will be found considerable diversity of opinion 
and of practice. The width of the beds, for instance — a matter 
of no small importance — has been the subject of sharp skirmish- 
ing between the advocates of the several plans. I take it, 
however, that among those best qualified to give an opinion or* 
laying out land for this purpose, certain principles may now be 
considered definitely settled. That the irrigation should be by, 
surface application, by overflow from grips or carriers, and not 
by the old fashioned and expensive method of hose and jet ;. 
that open carriers (as being the least expensive and the handiest), 
should conduct the sewage to convenient points for distribution, 
whence smaller courses should convey it along the centre of 
raised-up beds or ridges (resembling the high-backed lands sO' 
well known in certain districts) ; that the drainage should be 
deep and thorough, and the subsoiling perfectly accomplished j 
