price, but of late samples
containing 70 per cent of phosphates have sold as low as L4: 10s. per
ton, and consequently pure phosphates in this form are worth L6: 8s. per
ton. Although these are the only forms in which phosphates are
purchased alone, it is possible to determine the price at which they are
sold in bones and phosphatic guanos, by first deducting the value of the
ammonia they contain, and assuming the remainder to represent the price
paid for the phosphates. In this way we find the following values for
insoluble phosphates:--

In Coprolites L4 10 0
Bone-ash 6 8 0
Bones 7 5 0
Phosphatic guanos 10 0 0

It is to be observed that these are actual prices, and they are liable
to fluctuate with the state of the market, although they are pretty fair
averages. It is important to notice how much they vary in the different
forms; the farmer who buys a phosphatic guano paying for phosphates a
much higher price than he could have obtained those for in other
substances--a difference which must be attributed to the high state of
division in which they exist in the guano. We do not here enter upon the
question how far this difference in price is justified; we are content
with the fact that it exists, and we are compelled to estimate the value
of phosphates in a phosphatic guano at the price given above, although
in Peruvian guano they are sold at a lower rate. For all other manures,
of which bones and bone-ash form the basis, L7 may be taken as a fair
price, and it is that usually adopted, though L8 and L10 have sometimes
been assumed as the average.

_Ammonia_ is met with in commerce as muriate and sulphate of ammonia.
The former, owing to its high price, is practically excluded from use as
a manure; the latter sells at present at from L15 to L15: 10s. per ton,
and, making allowance for the usual amount of impurity (5 or 6 per
cent), the actual ammonia is worth about L63 per ton. Calculating from
other substances it appears that ammonia is worth, per ton, in--

Sulphate of ammonia L63 0 0
Bones 61 0 0
Peruvian guano 57 0 0

the average being L60, which is the price usually adopted.

_Sulphate of Lime_ and _Alkaline Salts_ (consisting chiefly of soda) are
generally estimated at Ll per ton; and potash in those cases, in which
it is necessary to take it into account, is usually valued at from L20
to L30 per ton, the former being its