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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 configuration of the earlier period with equal fidelity.
Fig. 7.—Stereogram of the Head of Chesapeake Bay
Fortunately, the Delaware Bay of the later Quaternary has an existing homologue by which conceptions of the local physiography and the attendant biotic conditions may be rendered tangible—viz., the head of Chesapeake Bay, shown in Fig. 7. This estuary is broad and shallow, as was the Delaware estuary during
