47

wheat depends almost exclusively on the quantity of nitrogen
in. the grains; those containing relatively the least of it,
being at the same time the most perfectly developed; they
are the heaviest, largest in size, and produce the finest qual-
ity of flour. The application of nitrogen to soils, (in the
form of ammonia,) therefore, not alone increases the yield of
the crop far above the proportion which we at first should
anticipate; but it also improves the quality of the produced
grain, and thus secures for it the highest price in market.

It has already been remarked that the quantity of ammonia
which a soil contains, or is capable of producing, is generally
in proportion to the quantity of humus in it. This latter
substance, though free of nitrogen itself, is always accom-
panied by nitrogenous matters, which, as integrant parts of
the plant, necessarily decay with its whore body, and becomes
thus intimately incorporated with the humus produced. The
nitrogen amounts to about 1-15 of the quantity, of carbon of
which the humus is composed.

But there is, independently of the supply of ammonia by
humus, another source for the acquisition of this nutriment,
which is inherent to the body of the soil at large, and there-
fore also dependent on the mechanical texture of the soil. It
has been proven that all soils have more or less the property of
attracting the ammonia contained in the atmosphere, and to
retain it in a state of combination, which so tightly locks it
up in the body of the soil, that it is impossible to extricate
it again with water. Water even, which has been saturated
with ammoniacal salts, if suffered to filter through soil, runs
off clear at the expense of the ammonia formerly contained
in it; as also an atmosphere charged with gaseous ammonia
is deprived of it when brought in contact with soil. In all
these cases the ammonia is found to have been appropriated
by, and incorporated with the soil. Prof. Way recently dis-
covered by his most tedious labors, that a certain class of arti-
ficial double silicates exercise, in this respect, a power similar
to that of soils, and, for several reasons, he concluded that it
was to the presence of portions of these double silicates that
soils owed the power above alluded to. Among them the
double silicate of lime and alumina was found to be that to
which this absorptive power of soils has chiefly to be attrib-
uted; this substance is a constituent part of clay, through the
mass of which it is diffused in minute particles, and therefore
never absent in soils. But if, in accordance with the above,
the power of soils for absorbing ammonia is increased with
the quantity of clay in them, it is on the other side neces-
sarily lessened again in proportion to the degree of stiffness