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NEW YORK STATE MUSEUM 



of the great interior glacial lakes) at its western border. Each of 

 these streams built extensive deltas into the lake. The magnitude 

 of these deltas affords evidence of a prolonged period of stable con- 

 ditions of the Lake Albany waters. 



When at length the waters of Lake Albany began to subside the 

 great deltas emerged as land surfaces. The emergence of the delta 

 of the Mohawk influenced greatly the subsequent drainage history 

 of the Mohawk-Hudson region. As the waters shallowed at the 

 head of the delta near Schenectady, the checked Iroquois-Mohawk 



Fig. 9 Sketch map showing areal extent of Lake Albany and drainage 

 courses on the areas of the Schenectady and Cohoes quadrangles at the 

 time when the Lake Albany waters had subsided to the level represented 

 by the present 320-foot contour 



currents, impeded by their own deposits, were diverted northeast- 

 ward through the Ballston channel, the latter opening into Lake 

 Albany in the Saratoga^Round Lake region. At the same time, 

 due to partial obstruction of the Ballston channel by sediments, a 

 spillway across the barrier of rocks at Aqueduct was formed and 

 a portion of the Mohawk waters discharged into Lake Albany at 

 Vischer Ferry. 



The northward course of the Mohawk waters continued for a 

 long time. As the subsidence of Lake Albany progressed, bringing 

 to the surface the lake bottom in the region of East Line, the cur- 

 rents eroded channels in the lacustrine deposits and eventually 



