36 - NEW YORK STATE MUSEUM 



Northville and the canyon of the upper Hudson, so much as then 

 existed. These waters at their lowest level must have been 840 plus 

 70 feet for tilting, making the water 900 feet at Northville and 

 Corinth. The Sacandaga at Northville is now 740 feet, and the 

 Hudson at Corinth is today only 520 feet. 



When the Schoharie lake was succeeded by the Amsterdam lake 

 the Hudson valley was still blockaded and the lake covered North- 

 ville ; but when the Amsterdam water fell to about 750 feet, on the 

 Gloversville parallel, the Sacandaga-Hudson waters became a dis- 

 tinct lake, with outlet southward by a pass four miles southeast of 

 Gloversville, at 760 feet. For two miles below the col this outlet is 

 a fair channel, but half way to Johnstown it becomes narrow, though 

 in shale, and unsatisfactory as an outlet channel of a large lake. 

 However, with the present conception of the events connected with 

 the ice recession it seems positive that the Sacandaga-Hudson waters 

 must have outflowed here into Lake Amsterdam. This tributary 

 lake must have persisted until the recession of the ice in the Sara- 

 toga and Ballston district opened a lower escape for the Hudson 

 waters at South Corinth. The Saratoga topographic sheet shows 

 the pass at South Corinth, at 636 feet, leading southward to the 

 Kayaderosseras creek. The valley of this stream shows excellently 

 the work of a short-lived river of high gradient and large volume. 

 Below Middlegrove and at Rock City Falls the valley walls are 

 severel)^ cut and heavy deposits of coarse cobble detritus lie far 

 above the present stream. The very extensive sand plains at Balls- 

 ton Spa and northward are the delta built by the glacial Hudson, 

 debouching at above 400 feet altitude in the late Amsterdam or early 

 Albany lake. This escape of the Hudson waters would seem to 

 have existed as late as the close of Lake Amsterdam and the estab- 

 lishment of Lake Albany over the Schenectady district. 



The name for this lake was given by Professor Brigham, who has 

 briefly described the Northville deltas (see title 6, pages 26, 27). 

 Plate 8 indicates in a general way the features of the Northville 

 district. 



THE ROCK BARRIER AT LITTLE FALLS 



One questionable factor in the glacial history is the effect on the 

 drainage and the time of the downcutting of the rock col at Little 

 Falls. 



In a former paper (see title 17, pages 22, 30-33) the writer 

 attributed some features in the Mohawk valley above Little Falls 

 to the ponding effect of the rock barrier, with perhaps some help 



