56 NEW YORK STATE MUSEUM 



Vail Mills it turns back on itself by making a sharp swerve north- 

 ward and then northeastward to empty into the Sacandaga river. 

 The course of Hans creek is similar though not quite so striking. 

 In preglacial time these streams were doubtless tributary to the 

 Sacandaga when it flowed southward into the Mohawk (see figure 

 10). The accumulation of drift across the southern border of the 

 quadrangle, which caused the northeastward deflection of the 

 Sacandaga, also caused a deflection of Kennyetto and Hans creeks 

 by forcing them to flow northward down the slope of the great drift 

 dam (interlobate moraine). 



Mayfield creek is postglacial in origin and has come into exist- 

 ence by finding a northeasterly channel down the slope of the 

 morainic belt. 



Batchellerville creek. During preglacial time the Batchellerville 

 fault trough had in it a considerable stream (Batchellerville creek) 

 which flowed south-southwestward, past Batchellerville and North- 

 ampton, as a tributary of the Sacandaga. The filling up or aggrad- 

 ing of this preglacial channel during the Ice age and the deflection 

 of the Sacandaga northward through this filled channel affords a 

 fine illustration of complete reversal of drainage. 



Lake Sacandaga. Immediately after the final disappearance of 

 the great ice sheet from this region, all of the present river flat area 

 as well as the area of the great swamp known as the *' Vly " were 

 covered by the waters of Lake Sacandaga which has been named 

 and described by Professor Brigham.^ It is interesting to note that 

 the great Sacandaga reservoir proposed by the State would almost 

 exactly restore what was once a natural lake. 



SUMMARY OF GEOLOGIC HISTORY 

 Because of the variety and complexity of the geologic problems 

 involved it seems advisable to give, in regular order, a summary 

 of the geologic history as exhibited within the quadrangle as well 

 as some idea of the relation of this history to that of the Adi- 

 rondacks in general.^ The combination of such a variety of rock 

 formations is due to the favorable situation along the border of the 

 Adirondacks where the Precambric crystalline rocks are overlapped 

 by the unaltered Paleozoic sediments. 



The definitely known history of the quadrangle begins with this 



1 N. Y. State Mus. Bui. 121, p. 26. 



2 For this broader outlook upon the subject the writer feels especially in- 

 debted to Professor H. P. Gushing who, for many years, has so zealously 

 and ably labored to unravel the intricate history of the Adirondack region. 



