2.57
Magnesia 0.30
Sulphuric acid 2.55
Silica 0.30
------
100.00
Ammonia which the organic matter }
is capable of yielding } 4.80

In general, bones may be said to contain about half their weight of
phosphate of lime, and 10 or 12 per cent of water. But, in addition to
their natural state, they are met with in other forms in commerce, in
which their organic matter has been extracted either by boiling or
burning. The latter is especially common in the form of the spent animal
charcoal of the sugar refiners, which usually contains from 70 to 80 per
cent of phosphate of lime, but when deprived of their organic matter,
they may be more correctly considered under the head of mineral manures.

From the analysis given above, it is obvious that the manurial value of
bones is dependent partly on their phosphates and partly on the ammonia
they yield. It has been common to attribute their entire effects to the
former, but this is manifestly erroneous; and although there are no
doubt cases in which the former act most powerfully, the benefit derived
from the ammonia yielded by the organic matter is unequivocal. When the
phosphates only are of use, burnt bones or the spent animal charcoal of
the sugar refiners are to be preferred.

At their first introduction, bones were applied in large fragments, and
in quantities of from 20 to 30 cwt., or even more, per acre, but as
their use became more general they were gradually employed in smaller
pieces, until at last they were reduced to dust, and it was found that,
in a fine state of division, a few hundredweights produced as great an
effect as the larger quantity of the unground bones. Even the most
complete grinding which can be attained, however, leaves the bones in a
much less minute state of division than guano, and they necessarily act
more slowly than it does, the more especially as they contain no
ready-formed ammonia. They may be still further reduced by fermentation,
which acts by decomposing the organic matter, and causing the production
of ammonia; but not as is frequently, though erroneously supposed, by
converting the phosphates into a soluble condition, for this does not
occur to any extent, and their more rapid action is solely due to the
partial decomposition of the organi