THE SCENERY OF THE COAL PERIOD. 



163 



Subsequent geological agencies have greatly modified 

 the primary result. The ocean has been permitted still 

 again to sweep over the continent, and the crests of the 

 folds and ridges have all been planed down, and the ma- 

 terials distributed over the intervening spaces, or worked 

 up in the rock-building of later ages. Thus the original 

 height of the Alleghanies has been much reduced. Thus 

 the swell upon which the Queen City of the West is built 

 has been worn off to the level of the adjacent areas ; and 

 thus the original limits of the great Carboniferous jungle 

 have been very much restricted. 



Pecopteris. Frond of an ancient Tree-fern. 



