ey
consist of structural details difficult to present in a popular form and
uninteresting to all but the professional naturalist. Suffice it to say,
that, though the organic world had the same general character in these
two closely allied periods, yet its representatives in each were
specifically distinct, and their differences, however slight, are as
constant and as definitely marked as those between more widely separated
creations.

At the close of the Devonian period, several upheavals occurred of great
significance for the future history of America. One in Ohio raised the
elevated ground on which Cincinnati now stands; another hill lifted
its granite crest in Missouri, raising with it an extensive tract of
Silurian and Devonian deposits; while a smaller one, which does not
seem, however, to have disturbed the beds about it so powerfully, broke
through in Arkansas. At the same time, elevations took place toward the
East,--the first links, few and detached, in the great Alleghany chain
which now raises its rocky wall from New England to Alabama.

In the Ohio hill, the granite did not break through, though the force of
the upheaval was such as to rend asunder the Devonian deposits, for we
find them lying torn and broken about the base of the hill; while the
Silurian beds, which should underlie them in their natural position,
form its centre and summit. This accounts for the great profusion of
Silurian organic remains in that neighborhood. Indeed, there is no
locality which forces upon the observer more strongly the conviction of
the profusion and richness of the early creation; for one may actually
collect the remains of Silurian Shells and Crustacea by cart-loads
around the city of Cincinnati. A naturalist would find it difficult to
gather along any modern sea-shore, even on tropical coasts, where marine
life is more abundant than elsewhere, so rich a harvest, in the same
time, as he will bring home from an hour's ramble in the environs of
that city.

These elevations naturally gave rise to depressions between themselves
and the land on either side of them, and caused also so many
counter-slopes dipping toward the uniform southern slope already formed
at the north. Thus between the several new upheavals, as well as between
them all and the land to the north of them, wide basins or troughs were
formed, inclosed on the south, west, and east by low hills, (for these
more recent eruptions were, like all the early uphea