n the siliceous substance, which is the insoluble
part, shall be supposed resisting every effort of the elements towards
its dissolution, those compound masses upon the surface of the earth,
however endued with hardness and solidity, are gradually impaired by the
dissolution of some of their constituent parts, and by the separation of
others which are thus exposed to the ablution of water. In like manner,
by the resolution of the surrounding parts, the solid _silex_, which is
supposed to be insoluble, is removed from its bed, and thus suffers new
parts of the solid land to be exposed to those injuries of the air, by
which the general good of plants, of animals, and even of future worlds,
are consulted.

The solid land is resolved into stones, gravel, sand, earths, and clays;
all or either of these, by retaining moisture, and affording places for
the roots of plants, are disposed for vegetation in different degrees; a
mixture of the different earths being, upon the whole, the best suited
to that purpose; and this compound body, mixed with vegetable or animal
substances, becoming a most luxuriant soil.

Soils are thus formed, either by the resolution of the surface of that
land upon which they are to rest, or by the transportation of those
solid parts to be again deposited upon another basis. In this manner
soils are constantly changing upon the same spot; sometimes they are
meliorated, at other times impoverished. From the tops of the mountains
to the shores of the sea, all the soils are subject to be moved from
their places, by the natural operations of the surface, and to be
deposited in a lower situation; thus gradually proceeding from the
mountain to the river, and from the river, step by step, into the sea.
Countries are thus formed at the mouths of rivers in the sea, so long as
the quantities of materials transported from the land exceeds that which
is carried from the shore, by tides and currents, into the deeper water.

The soil, with which the surface of this earth is always covered more or
less, is extremely various, both with respect to quantity and quality;
it is found resting upon the solid parts; and those solid parts are
always more or less affected by the influences of the atmosphere near
the surface of the earth. Those parts of the strata which approach
the surface are always in a decayed state; and this sometimes may be
observed for very considerable depths, according as the quality of the
materials,