THE CARBONIFEROUS PERIOD. 69 
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 dis- 
tinct, and their differences, however slight, are 
as constant and as definitely marked as those be- 
tween more widely separated creations. 
At the close of the Devonian period, several 
upheavals occurred of great significance for the 
future history ot 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 Si- 
lurian and Devonian deposits ; while a smaller 
one, which does not seem, however, to have dis- 
turbed the beds about it so powerfully, broke 
through in Arkansas. At the same time, eleva- 
tions took place toward the East, — the first links, 
few and detached, in the great Alleghany chain 
which now raises its rocky wall from New Eng- 
land 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 ; w r hile the Silurian beds, which 
should underlie them in their natural position, 
