the Progress of English Agriculture. 833 = 567 
■atment, and as both have failed to be successful in an eco- 
mical point of view, no further reference need be made to 
ese processes. 
The experience of the best sewage farmers in England appears Means of puri- 
- prove that concentrated, or downward intermittent, filtration, ^^"^2 sewage. 
ten it can be practised, is the most perfect means of purifying 
;d getting rid of sewage. It, however, can only be successfully 
trried out with sewage deprived, by subsidence in settling- 
liks, of the greater part of its suspended matters ; for unless 
1)se matters are previously removed, they accumulate on the 
i face of the land, choke up its pores, and render it impossible 
t filter rapidly large volumes of sewage through the soil. The 
iiny character of these suspended matters causes many diffi- 
< ties in the application of sewage to land, especially if the soil 
inot sufficiently porous to allow the passage of large volumes 
t ough it in a given time. There are many heavy clay-soils in Clay soils unfit 
1 gland which, in my opinion, are alike unfit for concentrated "'"S^^'o"- 
a 1 ordinary sewage-irrigation, and the attempts to render them 
f for the reception of sewage can only result in ruinous ex- 
f ises either to the ratepayers or to the occupier of such land. 
I wnward intermittent filtration, no doubt, is an excellent means 
0 disposing of sewage, if suitable land can be found ; but what 
if:o be done, it may be asked, with the sewage in localities 
\iere clay-soils abound, or the land is so situated as to render 
i) gation impracticable ? In such a case, the best plan would 
a)ear to be to purify raw sewage, by means of chemical precipi- 
ti ng agents, sufficiently to admit of the clarified and partially 
p ified effluent being poured into a water-course without creating 
auisance. Numerous experiments with all kinds of precipi- 
ti ng agents, and the experience of others on a large scalc; 
h e led me to the conclusion that by far the most efficacious 
a , on the whole, the most economical precipitating agent is Crude sulphate 
( le sulphate of alumina, assisted by the addition of just enough "f'il"mi"a best 
1 1 m i-ii iii- i jTii? precipitating 
e to render the emuent slightly alkaline and to eiiect the ygent. 
iplete precipitation of the alumina from the crude sulphate, 
iimost cases sewage thus purified may be allowed to run into 
a ream of adequate dimensions, and in places where running- 
w er is not at hand, special filtering-beds must be prepared to 
-I ct the final purification of the clarified sewage. 
umming up briefly these remarks on the disposal of sewage 
1 England, I would observe : — 
. In my judgment, the most economical plan to dispose of Disposal of 
ten-sewage is to carry it, if possible, bodily far enough into towu sewage, 
tl open sea to destroy any chance of its being brought back 
in by the tide. 
. When sewage cannot be taken out into the sea, and land 
3 K 2 
