292 H. L. FAIRCHILD POST-GLACIAL SUBMERGENCE OF LONG ISLAND 



reiiee, augmented by the flood from the meltino; ice-sheet, passed out 

 through the Hudson Valley. Tlie writer knuws of no glacial water of 

 an\^ size and lengtli of life held up by a morainal dam. 



The only sites wliich can 1)e suggested for a drift dam are at the ter- 

 minal moraine (the Staten Island N'arrows) or in the constriction of the 

 valley at the Highlands (the West Point district). The blockade at the 

 NarroAvs would be inefi^ective with the Harlem Valley and Long Island 

 Sound open. With reference to barriers in the course of the great valley, 

 it is to be noted that at any place ^diere a dam can be proposed, in either 

 the Hudson or the Cbamplain section, the evidence of long-standing 

 water appears quite as high below (south of) the location as above (north 

 of) it. For example, at the Fort Edward divide, the only likely barrier. 

 heavy and conspicuous terraces and unquestioned proofs of standing 

 water lie continuous on both sides of the valley some 300 feet owv tlic 

 col. The idea of drift barriers has no basis in fact or sound theory and 

 may be dismissed. 



A rock dam or land barrier to hold the Hudson waters to the high 

 level can not be postulated except by lifting the offshore sea-bottom or 

 continental shelf, as Upham did long ago (8, page 486). We find that 

 the water plane projected south does not drop to sealevel until south of 

 New York City. The gratuitous land !)arrier would have to lie far out 

 to sea and reach around to New England, so as to block off Long Island 

 Sound. This conce])tion has no basis in evidence and may also be dis- 

 missed. There is no scientific explanation of the high level waters in the 

 Hudson Valley except as confluent with the open sea. And every fact 

 and argument also applies to the Connecticut and other low valleys of 

 New England. 



The deep submergence of the Hudson Valley since the ice removal is a 

 fact of geologic record, and it must be granted that neighboring territory 

 on the east was involved. But the proof of Long Island submergence is 

 not by any means limited to this indirect evidence. An abundance of 

 direct proof is found in the features of the island, which will be described 

 in later chapters. 



EVIDENCE FROM THE CONNECTICUT VALLEY 



In a former paper (28) the old problem of the Connecticut Valley 

 terraces was presented and the argument and evidence for submergence 

 briefly stated. Since that publication the study of the marine plane has 

 been prosecuted, and some evidences in the extreme north end of the 

 ancient Connecticut Valley are published in a Vermont report (30), 



The proofs of deep and long-li\ed waters in the Connecticut Valley 

 are the same as in the Hudson and equally convincing. But as the valley 



