arth; and there can be no doubt that
coal sometimes originates in this way, for much fossil coal shows
abundance of vegetable bodies in its composition.

There remains only to consider the change in the disposition of coal
strata. Coal strata, which had been originally in a horizontal position,
are now found sometimes standing erect, even perpendicular. This, also,
is consistent with our theory of the earth. Indeed, there is not a
substance in the mineral kingdom in which the action of subterranean
heat is better shown. These strata are evidently a deposit of
inflammable substances which all come originally from vegetable bodies.
In this stage of their formation they must all contain volatile
oleaginous constituents. But some coal strata contain no volatile
constituents, and the disappearance of the volatile oleaginous
substances must have been produced by distillation, proceeding perhaps
under the restraining force of immense compression.

We cannot doubt that such distillation does take place in the mineral
regions, when we consider that in most places of the earth we find the
evident effects of such distillation in the naphtha and petroleum that
are constantly emitted along with water in certain springs. We have,
therefore, sufficient proof of this operation of distillation.

_III.--The Disintegration and Dissolution of Land_

Whether we examine the mountain or the plain, whether we consider the
disintegration of the rocks or the softer strata of the earth, whether
we regard the shores of seas or the central plains of continents,
whether we contemplate fertile lands or deserts, we find evidence of a
general dissolution and decay of the solid surface of the globe. Every
great river and deep valley gives evidence of the attrition of the land.
The purpose of the dry land is to sustain a system of plants and
animals; and for this purpose a soil is required, and to make a soil the
solid strata must be crumbled down. The earth is nothing more than an
indefinite number of soils and situations suitable for various animals
and plants, and it must consist of both solid rock and tender earth, of
both moist and dry districts; for all these are requisite for the world
we inhabit.

But not only is the solid rock crumbling into soil by the action of air
and water, but the soil gradually progresses towards the sea, and sooner
or later the sea must swallow up the land. Vegetation and masses of
solid rock retard the seaward flo