734 J- HOWARD WILSON 



deposits. As the subsidence continued, the barrier beach, unable 

 to hold its own, allowed the seas to break into the lagoon, causing 

 a disturbance of the upper deposits, the formation of the fragment 

 bed, and the unconformity. Finally this outer bar became destroyed, 

 and the material of which it was composed was washed into the 

 lagoon, forming the upper white sand (No. 16). 



The next event which took place was the advance of the Wisconsin 

 ice-sheet over and beyond this region, eventually burying the deposits 

 under 50 feet or more of drift. This last advance of the great con- 

 tinental glacier may have pushed its front some distance to the south 

 of Nantucket, during which time, and during its retreat to the posi- 

 tion in which the Nantucket terminal moraine was formed, or during 

 the first part of this Nantucket stage, a re-elevation of the land to 

 its present position must have taken place. 



At any rate, from evidence gathered all over the island we know 

 that the land stood not far from its present level when the ice-front 

 occupied the Nantucket position. There is absolutely no evidence 

 to show that the Nantucket moraine, with its apron plain and other 

 characters, was formed below sea-level, or at any elevation essentially 

 different from that which it occupies at the present day. 



