REPORT OF THE DIRECTOR I915 183 



end of it can be seen from a distance of one-half of a mile from the 

 lower Crown Point-Ticonderoga road. It is so striking in appear- 

 ance that it looks like a railroad bed cut into the hillside (plate 3). 



THE MARINE INVASION 

 (Map 4) 



Until this last stage of the glacial lake was inaugurated, the ice 

 sheet had lain against the northern base of the Adirondack and 

 Green mountains, choking the northern end of the Qiamplain valley 

 and impounding the waters behind it. They drained southward 

 into the Hudson basin. As long as the glacier filled the basin of the 

 St Lawrence and choked the northern end of the Champlain valley, 

 the waters impounded behind it stood at levels relatively higher to 

 the sea, although the land itself was much lower than now. When, 

 however, the ice retreated from the northern base of the Green 

 mountains, the waters were allowed to escape at the north into the 

 St Lawrence gulf, and the level of the lake was lowered thereby. 

 Then, when the ice was no longer a barrier, the sea came in at a 

 lower level. Thus the Champlain valley was converted into an 

 inlet or estuary opening to the north. The marine waters extended 

 as far south as Benson's Landing or Putnam (Leighton, 1905, 

 p. 629), or to Whitehall according to Baldwin (Baldwin, 1894, 

 p. II). 



This episode is recorded by the presence of marine shells and 

 other marine fossils in the Champlain clays which were laid on 

 the valley floor at this. time. The shells of mollusks are very 

 common (Peet, 1904, p. 461-62). Near Charlotte, Vt., the bones 

 of a whale were found in clay about 8 feet below the surface. It 

 was a species of Beluga closely similar to B . 1 e u c a s or to 

 B. catodon (Dawson, 1883, and Vermont Geological Survey, 

 1849), species which live in the north Atlantic ocean at the present 

 time. 



Woodworth has correlated the beaches and terraces attributed 

 to the marine epoch along his line M-N on plate 28. This line 

 would pass the latitude of Putnam's creek at an altitude of approxi- 

 mately 1 8 1. 5 feet.^ 



1 Subsequent to the publication of his paper Woodworth, in company 

 with General Lamothe and Professor Goldthwaite, found marine shells on 

 Mount Royal at an elevation of 585 feet. Lamothe and Woodworth placed 

 the upper marine limit on Mount Royal at 625 feet. This would make 

 the rate of tilting along line M-N even steeper than given, that is, 4.1 11 feet 

 to the mile. But it would still pass through the Crown Point region some- 

 where between the 180 and 200 foot contours. 



