THE ARCH^OLOGICAL SIGNIFICANCE OF AN 

 ANCIENT DUNE. 



By CHARLES C. ABBOTT, M.D. 

 {Read December 7, 1917.) 



When solid rock is before us, its history is readily traced, its 

 place in geological sequence determined and its characteristics, 

 lithological and mineralogical, determined beyond dispute, but, when 

 this and associated rocks are reduced to a coarse powder or sand and 

 carried by water or borne by wind hither and yon, it is with diffi- 

 culty that the earlier chapters of the record of its career can be 

 deciphered. As words accumulate as books due to the winds of 

 doctrine, so, ridges, hillocks and undulating plains are formed when 

 the wind gains access to the sand and rearranges the same en masse 

 as the stable fixtures of the region determine. These are transient, 

 necessarily, every shifting of the wind changing the scenery, but 

 traces of some of these phenomena have, by lucky chance, survived 

 every vicissitude and it is possible to discover what remains of a 

 one-time dune that was shaped by the winds blowing over a desert- 

 like plain, and at a time when the ocean water filled the adjacent 

 river valley and the tributary brooks were filled with brackish water 

 due to the inflowing tide, and this at a point now fifty miles inland. 



In other words, here in the valley of the Delaware River, at the 

 head of tide water, but where the salt or brackish water now never 

 reaches, is what remains of a dune that formed on the bank of a 

 small creek, now diminished to a brook that itself is reduced almost 

 to the vanishing point during the drought of mid-summer, but has 

 been known to resume its former importance as the result of a 

 cloudburst or of a protracted but less impetuous rainfall. 



So changed now are all the conditions of a few thousands of 

 years ago, that it seems hopeless to reconstruct the surrounding 

 country at the time the dune was formed. This is a task, however, 



PROC. AMER. PHIL. SOC, VOL. LVII, D, JANUARY 3I, I918. 



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