34 



THE POPULAR SCIENCE MONTHLY. 



sonable accuracy the general features of the region ; and Fig. 6 is 

 a similar sketch of the region as it existed during the Trenton 

 gravel period, based upon the same surveys and upon the shore- 

 lines brought to light thereby, and probably represents the con- 

 figuration of the earlier period with equal fidelity. 





W if! I 



'mB'f 





mi 



Fortunately, the Delaware Bay of the later Quaternary has an 

 existing homologue by which conceptions of the local physiog- 

 raphy and the attendant biotic conditions may be rendered tan- 

 gible — viz., the head of Chesapeake Bay, shown in Fig. 7. This 

 estuary is broad and shallow, as was the Delaware estuary during 



