GEOGRAPHY OF THE EMPIRE OF REPTILES. 195 



CHAPTER XVH. 



THE GEOGEAPHY OP THE EMPIRE OF REPTILES. 



have been developed, like organisms, 

 from their primeval germs. Geologic force, like vital 

 force, operates always toward the accomplishment of some 

 definite end ; and, notwithstanding its vicissitudes, there is 

 little difficulty in perceiving how every phenomenon of one 

 age has been contemplated and ministered to by the events 

 of all .preceding ages. The American Continent is not a 

 single upthrow of volcanic force, but a gradual growth, be 

 ginning before the creation of the first animals and plants, 

 and proceeding by a certain method through all the subse 

 quent ages even to the present, and receiving from time 

 to time such progressively improved existences as its phys 

 ical circumstances permitted. At first it was an angulated 

 ridge of land in the centre of the present continental area 

 (Fig. 20). Then, by successive upheavals, belts of incre 

 ment were added on the southeast and southwest, till the 

 ancient ocean has been narrowed to its present limits. Like 

 the exogenous growth of an oak, the increase has been al 

 ways upon the outside. So the vast continent has been 

 built up and configurated in accordance with a method as 

 definite as that which has shaped the globe itself. 



The empire of molluscs saw the greater portion of the 

 continent the bed of the sea. The reign of fishes witnessed 

 the emergence of only the extreme northeastern and north 

 western portions of the United States (Fig. 55). In the 

 earlier part of the reign Of reptiles New England was a 

 peninsula hemmed in by the broad estuary of the St. Law- 



