_; if they are in the _interior_ of particles, they cannot be
made use of; while, if the particles are so pulverized that their
constituents are exposed, they become available, because water can
immediately attack to dissolve, and carry them into roots.

[What is one of the chief offices of plowing and hoeing?

Is the subsoil usually different from the surface soil?

What circumstances have occasioned the difference? In what way?]

This is one of the great offices of plowing and hoeing; the _lumps_ of
soil being thereby more broken up and exposed to the action of
atmospheric influences, which are often necessary to produce a fertile
condition of soil, while the trituration of particles reduces them in
size.

SUBSOIL.

[May the subsoil be made to resemble the surface soil?

May all soils be brought to the highest state of fertility?

On what examination must improvement be based?

What is the difference between the soil of some parts of Massachusetts
and that of the Miami valley?]

The subsoil is usually of a different character from the surface soil,
but this difference is more often the result of circumstances than of
formation. The surface soil from having been long cultivated has been
more opened to the influences of the air than is the case with the
subsoil, which has never been disturbed so as to allow the same action.
Again the growth of plants has supplied the surface soil with roots,
which by decaying have given it organic matter, thus darkening its
color, rendering it warmer, and giving greater ability to absorb heat
and moisture, and to retain manures. All of these effects render the
surface soil of a more fertile character than it was before vegetable
growth commenced; and, where frequent cultivation and manures have been
applied, a still greater benefit has resulted. In most instances the
subsoil may by the same means be gradually improved in condition until
it equals the surface soil in fertility. The means of producing this
result, also farther accounts of its advantages, will be given under the
head of _Cultivation_ (Sect. IV.)

IMPROVEMENT.

From what has now been said of the character of the soil, it must be
evident that, as we know the _causes_ of fertility and barrenness, we
may by the proper means improve the character of all soils which are not
now in the highest state of fertility.

Chemical analysis will tell us the _composition_ of a soil, and an
examination, such as any farme