for there are evidences of it afterwards; but probably the
superabundance of carbonic acid gas supposed to have existed during
this era was expended before its close. There can be little doubt
that the infusion of a large dose of this gas into the atmosphere at
the present day would be attended by precisely the same circumstances
as in the time of the carboniferous formation. Land animal life
would not have a place on earth; vegetation would be enormous; and
coal strata would be formed from the vast accumulations of woody
matter, which would gather in every sea, near the mouths of great
rivers. On the exhaustion of the superabundance of carbonic acid
gas, the coal formation would cease, and the earth might again become
a suitable theatre of being for land animals.

The termination of the carboniferous formation is marked by symptoms
of volcanic violence, which some geologists have considered to denote
the close of one system of things and the beginning of another. Coal
beds generally lie in basins, as if following the curve of the bottom
of seas. But there is no such basin which is not broken up into
pieces, some of which have been tossed up on edge, others allowed to
sink, causing the ends of strata to be in some instances many yards,
and in a few several hundred feet, removed from the corresponding
ends of neighbouring fragments. These are held to be results of
volcanic movements below, the operation of which is further seen in
numerous upbursts and intrusions of volcanic rock (trap). That these
disturbances took place about the close of the formation, and not
later, is shewn in the fact of the next higher group of strata being
comparatively undisturbed. Other symptoms of this time of violence
are seen in the beds of conglomerate which occur amongst the first
strata above the coal. These, as usual, consist of fragments of the
elder rocks, more or less worn from being tumbled about in agitated