832 = 566 Influence of Chemical Discoveries on 
Proved by 
analysis. 
Failure to 
purify by 
chemical 
agents. 
same area. Growing crops derive advantage mainly from tijtrf 
sewage held in the land mechanically, in the same manner \ 
which a sponge holds water ; and hence crops like Italian ry i 
grass, which consume a large quantity of liquid, and admit \ 
being repeatedly irrigated with sewage, are precisely the ki) 
of crops that are peculiarly well adapted to sewage irrigation. 
In proof of the fact that in light, porous, sandy soils, throuj 
which enormous quantities of sewage had been passed, 
material accumulation of fertilising matters took place by lo: 
continued irrigations with large volumes of sewage, attenti 
may be directed to an analysis which I made of the soil frt 
the noted irrigated Craigentinny meadows, near Edinburgh, 
The soil was found to contain in 100 parts : — 
*Organic matter 1-60 
Oxide of iron and alumina 1 "04 
Phosphoric acid -06 
Sulphuric acid traces 
Lime 
Magnesia .. 
Potash 
Soda 
Chloride of sodium 
•08 
•25 
•08 
•13 
•02 
Silica (white fine sand) 96 •SO 
100 • 06 
* Containing nitrogen 
Equal to ammonia 
•039 
•047 
It appears from this analysis, that notwithstanding the enj 
mous volumes of sewage which, in the course of many years, ' 
been poured upon this land, it contained only a little ab(J 
1^ per cent, of organic matter, and practically merely trac 
accumulated nitrogen. What little organic matter there wa 
the land, the examination showed not to be due to sewage, 
to consist of visible fibres of roots and similar organic remaji 
of the grass-crops grown upon the land. After irrigation w i 
large quantities of sewage for many years, the land, it will 
seen, is still a poor sandy soil, containing nearly 97 per centf { 
pure silica. 
Many attempts have been made of late years to purify sew; 3 
by various chemical precipitating agents, and to extract fron I 
at the same time fertilising matters, which in a dried and j - 
verised condition, are sold in England at prices varying fi i 
IZ. to ol. per ton. The manufacture of night-soil and to' • 
refuse into portable manure is carried on at Rochdale, Ilalil v 
Manchester, Oldham, and other towns ; but as neither the ma - 
facture of night-soil manures, nor the conversion of scw3 
deposits into portable manures, pays the contingent costs of 
I 
