To these dislocations of the strata we owe the
transverse cracks across the central part of New York, which needed
only the addition of the fresh water poured into them by the rains to
transform them into lakes.
I shall not attempt any account of the differences between the animals
of the Devonian period and those of the Silurian period, because they
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.
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