after careful observation we readily detect in it a regularity
and order from which much instructive light is thrown on its past
vicissitudes. The deposition of the aqueous rocks and the projection of
the volcanic have unquestionably taken place since the settlement of the
earth in its present form. They are, indeed, of an order of events which
are going on under the agency of intelligible causes, down to the
present day. We may therefore consider these generally as recent
transactions. But advancing to the far distant antecedent era of its
existence, we may consider it to have been a globe of its present size
enveloped in the crystalline rock already described, with the waters of
the present seas and the present atmosphere around it, though these were
probably in considerably different conditions, both as to temperature
and their constituent materials, from what they now are. We may thus
presume that, without this primitive case of granitic texture, the great
bulk of the matters of our earth were agglomerated, whether in a fluid
or solid state is uncertain; but there cannot be any doubt that they
continue to exist in a condition of great heat and compression, having a
mean density of more than double that of the minerals on the surface.

Judging from the results and still observable conditions, it may be
inferred that the heat retained in the interior of the globe was more
intense, or had greater freedom to act, in some places than in others.
These become the scenes of volcanic operations, and in time marked their
situations by the extrusion from below of trap and basalts--rocks
composed of the crystalline matter, fused by intense heat, and developed
on the surface in various conditions, according to the particular
circumstances under which it was sent up; some, for example, being
thrown up under water, and some in the open air, which contingencies
would make considerable difference in its texture and appearance. It
would, however, be a mistake to infer that, previous to these eruptions,
the earth was a smooth ball, with air and water playing round it.
Geology tells us plainly that there were great irregularities--lofty
mountains, interspersed with deep seas--and by which, perhaps, the
mountains were wholly or partially covered. But it is a fact worthy of
observation that the solids of our globe cannot for a moment be exposed
to water or the atmosphere without becoming liable to change. They
instantly begin to wear down