they assume, at the expense of their porosity and fitness to
communicate freely with the atmosphere, and is, therefore,
also dependent on the mechanical texture. Direct experi-
ments have shown that the mechanical texture of loamy soils
is the most favorable for the performance of this important
function of soils; this class of soils, though containing a con-
siderable quantity of clay, is famous for the porous condition
of its body, in consequence of which it will permit a free ac-
cess of the atmosphere to all its parts.

The means and ways for the improvement of the mechani-
cal texture of soils are various; it may be effected either by
a mechanical treatment of the soil itself, as by loosening,
deepening, draining, &c, or by extra additions being made
to it from without. Of these two methods of improvement,
only the latter is an act of manuring in the strictest sense of
the term, and subject to our consideration in this place. The
substances applied are such as will meet the deficiencies of the
one or the other of the fundamental constituents of soil, and
in this way restore a proper proportion of their relative quan-
tities. In accordance with this, they may be divided into four
classes of manure, viz: silicious, (supplying sand;) argilla-
ceous, (supplying clay;) calcareous, (supplying lime and mag-
nesia ;) and organic matter, (supplying humus.)

After the foregoing remarks, I will now treat, in particular,
of the various kinds of manure employed, whether designed
for the improvement of the mechanical texture or for the pur-
pose of increasing the directly nourishing capacity of soils,
and will present them in an order which, if not strictly sys-
tematical, will best lead to a full understanding of their
character and mode of action.

NITROGENOUS MANURES.

Stable or barn yard manure is indisputably the chief manure
of all, as it offers to the farmer the most natural and efficient
means for restoring fertility to his soil. It is formed of the
solid and liquid excrements of animals, together with the lit-
ter-straw of wheat or indian corn, and is consequently com-
posed of both classes of fertilizing substances; those which,
by their physical properties, improve the mechanical texture
of soils, as well as those which, being soluble in water, serve
as a direct nutriment to plants.

With regard to the former, stable manure acts principally
on account of its humus, the high importance of which as a
fundamental constituent of soils, has been repeatedly dis-
cussed in this and my former reports. Humus promotes the

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