nly on the phosphates, the animal matters and
other substances contained in them were not without effect. The action
of phosphates is greatly promoted by solution in sulphuric acid, and the
application of the acid has brought into use many varieties of
phosphates of purely mineral origin, or which have been deprived of
their organic matters by artificial processes. Of these, the spent
animal charcoal of the sugar-refiners, usually containing about 70 per
cent of phosphates, and South American bone ash, are the most important.
The latter is now imported in very large quantity, and has the
composition shewn in the following analyses:--

I. II. III.

Water 6.10 6.28 3.03
Charcoal 5.05 2.19 2.02
Phosphates 79.20 71.10 88.55
Carbonate of lime 4.05 3.55 5.60
Alkaline salts 0.15 traces ...
Sand 5.45 16.90 0.80
------ ------ ------
100.00 100.00 100.00

Bone ash has hitherto been almost entirely consumed as a raw material
for the manufacture of superphosphates; but as it is sold at from L4:
10s. to L5: 10s. per ton when containing 70 per cent of phosphates, it
is, in reality, a very cheap source of these substances, and merits the
attention of the farmer as an application in its ordinary state.

Of strictly mineral phosphates, a considerable variety is now in use,
but they are employed exclusively in the manufacture of superphosphates,
as in their natural state they are so hard and insoluble, that the plant
is incapable of availing itself of them.

_Coprolites._--This name was originally applied by Dr. Buckland to
substances found in many geological strata, and which he believed to be
the dung of fossil animals. It has since been given to phosphatic
concretions found chiefly in the greensand in Suffolk and
Cambridgeshire, which are certainly not the same as those described by
Dr. Buckland, but consist of fragments of bones, ammonites, and other
fossils. Coprolites are now collected in very large quantities, and
about 43,000 tons are annually employed. They are extremely hard, and
require powerful machinery to reduce them to powder, and hence their
price is considerable, being about L2: 10s. per ton. Their composition
varies somewhat according to the care taken in selecting them, and the
locality from which they have been obt