Use of Town Sewage as Manure. 
139 
little doubt that the attempt will be perfectly successful ; and it 
may be taken for granted, that in every considerable town ar- 
rangements will be made by the manufacturers of manure for the 
collection of all the blood which is produced, and it will soon 
cease to be a waste substance, in the true sense of the word, as 
bones have long ceased to be. 
I mention this merely to show that, in considering the nature 
of sewage, we must take into account the circumstances which 
are likely in course of time to influence that nature, and not 
build upon those conditions which evidently cannot be per- 
manent. 
In considering the subject of town sewerage in its application 
to agriculture we ought to take account only of those matters 
which will, under the most perfect system of sewage and with 
all the changes to which towns are being subjected, ultimately 
be so discharged. I have already stated that the increased trade 
in manures will (if no other use should be found for them), 
sooner or later, intercept from the sewers all those refuse matters 
which can be turned to any account in manure making. So of 
other substances which now constitute part of the sewage — the 
urine of cows kept in large towns will, of course, have hitherto 
contributed to the agricultural value of sewer water ; but this 
source of value is on the decline. In large towns, especially in 
the metropolis, the source of supply of milk is gradually being 
transferred from the unwholesome cow-yards of back lanes and 
alleys to its proper place, in the country, from whence purer 
milk can be sent by railroad with at least equal pecuniary advan- 
tage. Even in those cases where the feeding of cows in large 
towns is continued, it is quite probable that the urine will in 
course of time be collected for concentration into a powerful 
portable manure, of which it is well known to be capable. 
The urine of horses whilst in the stable is largely absorbed in 
their litter, and does not therefore much affect the composition 
of the sewer water. Throwing out from our calculations these 
various items, we shall find that the subject is very much nar- 
rowed, and that sewage water will have to be viewed mainly as a 
mixture of the solid and liquid excrements of a town population, 
with the water supplied for domestic and general use, and the 
rain-fall of the area washing the streets. No doubt other matters 
are, and always will be, conveyed away by the sewers, and ought 
strictly to be taken into account, but practically we should gain 
nothing by entering upon their consideration. We shall, there- 
fore, now direct our attention to the question of the excrementi- 
tious matter of a population, and the water with which it is 
removed. And first with regard to the quantity and value of 
solid and liquid excrements in town sewage. 
