The existence of the numerous smaller lakes running north and south in the State of New York, as the Canandaigua, Seneca, Cayuga, etc., is more easily accounted for.  Slow and gradual as was the process by which all that region was lifted above the ocean, it was, nevertheless, accompanied by powerful dislocations of the stratified deposits, as we shall see when we examine them with reference to the local phenomena connected with them.  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.

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 upheavals, insignificant in height,) and bounded on the north by the more ancient shores of the preceding ages.