0.10
Soda 0.06
Phosphoric acid 1.08
Sulphuric acid 0.16
Organic matter 17.95
Sand 20.51
Water 53.56
------
100.00
Ammonia 0.93

And even, though containing more than half its weight of water and 20
per cent of sand, this substance has considerable value as a manure.

The growing evils of the existing system of sewage, and the enormous
waste of a manurial matter, which the experience of the Craigentinny
meadows has shewn to be productive of the most important effects, has
recently directed much attention to the conversion of the contents of
our sewers into a useful manure. Numerous plans for its precipitation
and conversion into a solid manure have been proposed, but most of these
have shewn an entire ignorance of the fundamental principles of
chemistry, and the best only succeed in precipitating a very small
proportion of its valuable matters, and leave almost the whole of the
ammonia, as well as the greater part of the fixed alkalies, in solution.
Nor is it to be expected that any process will be discovered by which
these substances can be precipitated, because solubility is the special
characteristic of their compounds, and no means is known by which it is
possible to convert them into an insoluble form. If sewage is to be used
at all, there seems little doubt that it must be by applying it entire,
and in the liquid state. But here again, the expense of conveying it on
to the land becomes an obstacle which it must frequently be impossible
to overcome. When it can be conveyed by gravitation, as is the case in
the neighbourhood of Edinburgh, it may undoubtedly be used with the
utmost advantage, and with the very best economic results. But when it
requires to be carried to a great distance through pipes, and raised to
a high level by pumping, all these advantages disappear. If the cost of
application amounts to 2d. a gallon, as in Mr. Mechi's case, or even to
half that sum, it may be fairly concluded that it cannot be used with
any great prospect of large economic results, and that, unless under
very exceptional cases, it must be unprofitable.

The chances of success must also greatly depend upon the kind