Use of Town Sewage as Manure. 
157 
directly and I)y artificial heat would be plainly out of tlic ques- 
tion. Now the substance so used must be agriculturally ol less 
value than the dry faecal matter, or of more — if less, then the pro- 
duct would have a less value than is shown in the analysis above ; 
if more, then we are diluting^ the material of higher value by the 
addition of that of less — in other words, we are giving to the 
sewage manure a value which it does not intrinsically possess, 
by a costly addition — which is a commercial absurdity, unless it 
can be shown that the product obtained by the union of tlie two 
substances is better worth than either separately. 
Tliere is, however, still another point to be considered, and 
that is, can we by any chemical treatment retain a portion, or the 
whole, of the valuable matter which in the case of mere mecha- 
nical filtration passes ofiF in the liquid, and thus raise the standard 
of the solid products ? Can we stop the ammonia, the potash, 
and the pliosphoric acid, and add them to our stock in trade ? 
It is evident that the promoters of the plans which have been 
proposed, and many of those who, having no direct interest in 
them, are still on public grounds anxious for their success, think 
that this can be done, for we constantly hear that by such and 
such a process the ammonia and valuable alkaline compounds of 
the sewage are " fixed," and incorporated in the manure in a dry 
and portable shape ; and this brings us to consider — which, with- 
out disrespect to the subject, for it is very important, we shall 
do very briefly — the various substances that have been proposed 
for employment in the collection of sewage. 
These are the various forms of charcoal, lime, gypsum, clay, 
burnt and unburnt, salts of alumina, salts of zinc, of iron, and 
of magnesia, and certain compounds of silica. These have been 
proposed for use in some cases separately, in others two or 
more of them have been associated together in the process. 
And first, of charcoal, of which there are several forms. Bone 
or animal charcoal is made by burning bones in a close retort ; 
it is an excellent substance for deodorizing offensive matters, 
but too costly for use in this way. The supply is limited, and 
the price from 12/. to 13/. per ton ; its principal use is in sugar 
refining. Peat charcoal is also a good deodorizing substance ; 
it may be produced, as is well known, in large quantities in 
Ireland, in Yorkshire, Devonshire, in fact wherever large tracts 
of peat land occur. It would be very cheap, but for the fact 
that when first dry the peat contains a very large proportion of 
water. Even when dry the weight is of course much reduced by 
the destruction of the organic matter and its conversion into 
charcoal. For every ton of charcoal produced, many tons of the 
original peat have to be dug and moved, and much of the cost 
is due to this circumstance. Peat charcoal is, however, supplied 
