nimals, and many attempts have been made to preserve and
convert it into a dry manure. Urate is prepared by adding gypsum to
urine, and collecting and drying the precipitate produced. It contains a
considerable quantity of the phosphoric acid of the urine, but very
little of its ammonia; and as the principal value of urine depends on
the latter, it is necessarily a very inefficient method of turning it to
account. A better method has been proposed by Dr. Stenhouse, who adds
lime-water to the urine, and collects the precipitate, which, when dried
in the air, contains 1.91 per cent of nitrogen, and about 41 per cent of
phosphates. This method is subject to the same objection as that by
which urate is made, namely, that the greater part of the ammonia is not
precipitated. This might probably be got over to some extent by the
addition of sulphate of magnesia, or, still better, of chloride of
magnesium, which would throw down the phosphate of magnesia and ammonia.
By much the best mode of employing urine is in the form of sulphated
urine, which is made by adding to it a sufficient quantity of sulphuric
acid to neutralize its ammonia, and evaporating to dryness. In this form
all the valuable constituents are retained, and excellent results are
obtained from it. Its effects, though mainly attributable to its
ammonia, are also in part dependent on the phosphates and alkaline salts
which it contains; and it is therefore capable of supplying to the plant
a larger number of its constituents than the animal matters already
mentioned.

_Night-Soil and Poudrette._--The value of night-soil, which is well
known, depends partly on the urine, and partly on the faeces of which it
is formed. Its disagreeable odour has prevented its general use, and
various methods have been contrived both for deodorising and converting
it into a solid and portable form. The same difficulties which beset the
conversion of urine into the solid form occur here, and in most of the
methods employed the loss of ammonia is great. It is sometimes mixed
with lime or gypsum, and dried with heat, and sometimes with animal
charcoal or peat charcoal. The manufacture of a manure from night-soil,
called "poudrette," has long been practised in the neighbourhood of
Paris and other continental towns. The process employed at Montfaucon
and at Bondy is very simple. The contents of the cesspools are conveyed
to the work in large barrels, which are then emptied into tanks capabl