ich consists of
a mixture of sulphates and chlorides of potassium and magnesium, has
also been suggested for this purpose. By using such a fixer, the value
of the resulting manure would be much enhanced. In conclusion, it must
be remembered that all the above-named fixers act very much in the same
way--viz., by converting the volatile carbonate of ammonia into sulphate
of ammonia.[156]

2. _Cow-manure._

The composition of the manure formed from the excrementitious matter of
the cow is very much less constant than is the case in the horse-manure.
An average statement of that composition is therefore very much more
difficult to obtain. The number of analyses available for the purpose of
forming this average is, however, very large. The manure produced by
cows contains a large percentage of water. This is due to the large
quantity of water they drink. It has been estimated that milch-cows
drink along with their winter food, for every pound of dry substance, 4
lb. of water, and in summer about 6 lb.

According to some experiments by Boussingault, the excrements of a cow
in a day amounted to 73.23 lb., of which only 9.92 lb. were dry
matter.[157] These excrements contained .256 lb. of nitrogen and 1.725
lb. of mineral matter. The amount of straw necessary to use as litter
for this amount of excrements may be taken at 6 to 10 lb. The manure,
therefore, formed by a cow per day, would contain from .274 to .286 lb.
of nitrogen, and from 2.046 to 2.278 lb. of mineral matter. In a year
this would amount to from 100 to 104.4 lb. of nitrogen, and from 746.8
lb. to 831.5 lb. of mineral matter; or from 6 cwt. 75 lb. to 7 cwt. 47
lb.

Cow-dung is, owing to its more watery nature and poorer quality, very
much slower in its fermentation than horse-dung. When applied alone,
cow-manure is very slow in its action, and makes its influence felt for
at least three or four years. It is difficult to spread it evenly over
the soil, owing to the fact that, when somewhat dried, it has a tendency
to form hard masses, which, when buried in the soil, may resist
decomposition for a very long period. The cause of this is due to the
presence of a considerable amount of mucilaginous and resinous matter in
the solid excreta, which prevents the entrance of moisture and air into
the centre of the mass. This tendency of cow-manure to resist
decomposition will be greatly lessened in the case of the excrements of
a cow richly fed.

The risks of loss o