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NEW YORK STATE MUSEUM 



The lake, then greatly narrowed, began to take on the char- 

 acter of a broad river and strong currents, coming both from the 

 north and from the Iroquois-Mohawk which still discharged into 

 the Hudson waters at Mechanicville, cut deeply into the sediments 

 still filling the midportion of the general Hudson valley. 



As a result of downcutting, symmetrical erosion terraces were 

 developed at two levels on opposite sides of the valley at Mechanic- 

 ville. The locations and configurations of these terraces show 



Fig. II Sketch map showing drainage of the areas of the Schenectady 

 and Cohoes quadrangles and breadth of waters occupying valleys when Lake 

 Albany had receded to the level represented by the present lOo-foot contour 

 line and had taken on the character of a broad river. The Mohawk river 

 had lowered its gorge at Aqueduct to the 300-foot level. 



conclusively that they were the work of the Iroquois-Mohawk 

 currents and establish the fact that the postglacial body of waters 

 of the Hudson valley became greatly diminished prior to the time 

 of the opening of the channel northward to the Adirondack region 

 as the outlet of the waters of the great interior lakes. 



The spillway across the rock barrier at Aqueduct gradually deep- 

 ened, through erosion, into a gorge of capacity sufificient to contain 

 the volume of the Mohawk waters. The flooded currents cut a 

 broad path through the lacustrine deposits southeast of Crescent, 

 laying bare the rock floor of the preglacial Hudson valley. Where 

 the river flowed over the rocky slope which marked the rim of the 



