THE LONG ISLAND COAST. 



443 



ness of the upper portions may suggest a shoaling of the coast from 

 an upward movement of the land as the Ice period came on. 



That an elevation occurred during the progress of the Ice period 

 is evident from the contour, as well as structure, of the drift of Long- 

 Island. On the north side of the island are numerous fiord valleys, 

 constituting a series of harbors of unsurpassed beauty. They extend 



I" "' -' WnliHi VI ' ' L " 



1. Surface gravel, 30 feet. 

 b- 2. Quicksand. 



3. Bowlder-drift, 70 feet. 



4. Clay, 27 feet. 



5. Oyster-shells, i foot. 



6. Coarse sand. 

 Fig. 3. Section of the Nassau Gas-Light Company's Well in Beookltn. 



into the island from two to six miles, having depths of w T ater from 

 tan to thirty, and in some instances fifty feet. Beneath the water is 

 a deep deposit of ooze or sediment, known to be in one case forty 

 feet thick. The banks on either side are from a few feet to 200 feet 

 hifWi. 



It is apparent that these enormous valleys were not wholly cut 

 into the drift after it was deposited, but rather were maintained 

 while the deposit of drift was in progress, as valleys or water-courses, 

 through which glacial streams may have been discharged into the 

 ocean. These became filled, however, by an excessive accumulation 

 of drift, as from rapid wasting of the ice, causing the outflowing 

 streams to be arrested, and the waters to be discharged eastward or 

 westward from Long Island Sound. But whether they were formed as 

 we suggest, or were cut into the drift after it was deposited, it is quite 

 certain that the coast was sufficiently elevated to permit the glacial 

 floods to sweep the bottom of those valleys. 



The 70 feet of drift of the Nassau Gas-Light Company's well is 

 wholly below tide, and its unmodified structure shows that it was de- 

 posited above the sea-level, or out of the reach of waves, and further 

 confirms the elevation of the coast in the glacial period. 



But evidence of the elevation of the coast during the progress of 



