PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOROUGH OF QUEENS 663 



made when there were no barrier beaches, are beneath the present 

 sealevel.^ 



Wherever the breadth of water is sufficient, however, and the 

 depth too great to permit of marsh growth the bay shores are now 

 being cut back in a marked manner by wave action, as at Cooper 

 Huff. 



Evidence of local depression of the shore line is found in beds of 

 peat extending outside of the beach below low tide level. Such a 

 bed, containing a flattened log, w^as exposed in the summer of 1900 

 at the northeast end of the barrier beach uniting Prospect point with 

 Sands point. Peat was also exposed on the front of the beach at low 

 tide half a mile southeast from Prospect point. In view, howev^er, of 

 the compressibility of the original swamp deposits, these localities 

 can hardly be regarded as proofs of a general sinking of the 

 island.^ 



It is questionable whether even measurable evidence of a slight 

 depression of the shore line along a coast of incoherent and yielding 

 materials such as the clays and gravels of the north coast of Long 

 Island may be taken as evidence of a movement of the continent. 

 There is a slow movement of the loose materials toward the shore in 

 many high bluflis. At Ragged Land point east of Northport harbor 

 this movement in clays has developed a landslide structure, a pro- 

 cess which presumably has been continuous since the suggestive 

 name was given to the irregular projection which these clays make 

 on the beach. They move with something like glacial flow, over- 

 running the normal beach, the wave action being there unequal to 

 the task of maintaining a straight shore line. 



^ De la Beche appears to have first made this point in the case of certain British 

 beaches. See Geological manual. Phil. 1882. p. 73-75. 

 2 Suess, Edouard. La face de la terre. Paris 1900. 2 : 670-89. 



