, and within a
week after the application, the difference between the dressed and
undressed portions of a field is already conspicuous. Experience has
shewn that success is best insured when the salt is applied during or
immediately before rain, so that it may be at once incorporated with the
soil; as when used in dry weather little or no benefit is derived from
it. It seems also to exert a peculiarly beneficial effect upon clover;
and hence it ought to be employed only on clover-hay, as where ryegrass
or other grasses form the whole of the crop we have better manures.

_Ammoniacal Liquor of the Gas-Works, and of the Animal Charcoal
Manufacturers._--Both of these are excellent forms in which to apply
ammonia, when they can be obtained. The ammoniacal liquor of the
gas-works is very variable in quality, but contains generally from 4 to
8 ounces of dry ammonia per gallon, which corresponds in round numbers
to from 1 to 2 lb. of sulphate of ammonia. It is best applied with the
watering-cart, but must be diluted before use with three or four times
its bulk of water, as if concentrated it burns up the grass, and it is
also advisable to use it during wet weather. The ammoniacal liquor of
the ivory-black works contains about 12 per cent of ammonia, or about
four or five times as much as gas liquor. It has been used in some parts
of England, made into a compost, and applied to the turnip and other
crops, and, it is said, with good effect. _Bone oil_, which distils over
along with it, has also been used in the form of a compost; it contains
a large quantity of ammonia and of nitrogen in other forms of
combination; the total quantity of nitrogen it contains being 9.04 per
cent, which is equivalent to 10.98 of ammonia. Only part of this
nitrogen is actually in the state of ammonia; and some circumstances
connected with the chemical relations of the other nitrogenous compounds
in this substance render it probable that they may pass very slowly into
ammonia, and may therefore be of inferior value; but the substance
deserves a trial, as it is very cheap. It must be carefully composted
with peat, and turned over several times before being used.

_Nitrates of Potash and Soda._--Nitrate of potash has long been used as
a manure, but its high price has prevented its general application, and
its place has now been almost entirely taken by nitrate of soda, which
is much cheaper and contains weight for weight a larger quantity of
nitrogen.