ijQUlVOCAL FEATUtlES xiBSENCE OF BEACHES 80^ 



raised to its present height. Before salt water was admitted to the 

 Champlain Valley, through the Saint Lawrence Gulf, the divide at Fort 

 Edward perhaps was raised above sealevel. The total uplift there has 

 been about 440 feet, and the col today is 150 feet above tide. 



CREASES ON THE PLAIN 



All writers on the physical features of the island have noted the pe- 

 culiar characters of the drainage lines. The variety of names applied, 

 as "dry rivers," "creases/' "furrows," etcetera, indicates tliat they are 

 unusual, indeiinite, and puzzling. Such careful workers as Salisbury 

 and Woodworth have referred to them as anomalous in form and doubtful 

 in origin. The earliest writers did ]iot recognize the glacial outwash of 

 the higher parts of the plain, and later writers failed to see the subaque- 

 ous origin of the lower plain. We now know that quite all of the east 

 lialf of the island and the entire extent of the south shore were under the 

 sea while all the subaerial outwash was building. There was dual origin 

 of the sand-plains, with different drainage features. Writers have not 

 discriminated, but have discussed the features as a whole. The channels 

 of the moraine and outwash should be treated distinct from the depres- 

 sions in the marine plain. The fullest description of the former is by 

 Fuller (27, pages 46-48). No one has specially described these sub- 

 marine features of Long Island; but Shaler^s discussion of similar forms 

 on the marine plains of the islands off the Massachusetts coast may l^e 

 sufficient :^ 



"The formation of this inclined plain of sisnd beneath the level of the sea 

 fully accounts for its general features; for in all respects, except in the pres- 

 ence of the channels before described, it essentially resembles the bottom of 

 the sea as it exists south of this shore. The angle of the slope seaward is the 

 same and, so far as we can judge by the soundings, the character of the ma- 

 terials in the two terraces does not differ hi any important respect. The only 

 difference is that on the existing sea-floor there appear to be no such channels 

 as we are endeavoring to explain. We are therefore fairly driven to seek the 

 origin of these channels in some forces which were at work during the glacial 

 period, and there are no others which seem available save the subglacial 

 streams, the existence of which is proven co us in many ways" (page 318). 



"These troughs generally terminate in the various ponds or coves which 

 indent the southern sho]-e of the island (Marthas Vineyard). In fact, these 

 inlets are formed in the southerly extremity of the depressions, where they 

 deepen toward the sea and have been widened by its action. . . . These 

 depressions are best studied on the similar southern plain of Nantucket, where 

 the treeless character of the surface clearly reveals their form. The striking 



* Report on the geology of Marthas Vineyard. Seventh Ann. Rept., U. S. Geo]. Sur- 

 vey, 1888, pages 297-363. 



