54 NEW YORK STATE MUSEUM 



distant, it lies at 1250 feet thus giving a southwestward slope of 

 100 feet per mile where the Precambric is not now covered by the 

 Paleozoic. The slightly lessened slope in this case has been due 

 to a reduction of level by erosion since the removal of the Paleozoic 

 sediments. The Hoffman's Ferry fault may have somewhat affected 

 the Precambric slope here but more than likely not enough to make 

 any material difference in the result. In other portions of the quad- 

 rangle the faults have so affected the slope that any results are 

 unsatisfactory. 



DRAINAGE OF THE QUADRANGLE^ 



Sacandaga river. As a result of the Ice age the drainage of the 

 quadrangle, including the four largest streams, has been very 

 notably affected. The most striking change has taken place in the 

 course of the Sacandaga. This river, after emerging from the 

 Adirondacks, enters the Paleozoic lowland between Northville and 

 Northampton and at the latter place turns back sharply (north- 

 northeastward) on its course past Batchellerville and Day and then 

 across a divide in the Precambric at Conklingville soon to enter the 

 Hudson at Luzerne. It is certain that, before the Ice age, the 

 Sacandaga river continued southward from Northville and was 

 tributary to the Mohawk. Its preglacial channel doubtless passed 

 between Broadalbin and Mayfield, because here the Paleozoic rocks 

 are the lowest within the quadrangle. That the course past Conk- 

 lingville is postglacial is proved by the gorge at that village; the 

 almost imperceptible gradient of the river between Northampton ; 

 and by the perfectly aggraded character of the river channel be- 

 tween the two villages just named. The remarkable deflection of 

 the course of this river was due to the great accumulation of glacial 

 drift, especially in the interlobate moraine, acting as a dam across 

 the southern portion of the Broadalbin sheet. The deflection was 

 aided by the presence of the deep trough of the Batchellerville fault 

 and also probably by a comparatively low preglacial divide at 

 Conklingville. 



According to borings for a dam site made by the New York 

 Water Commission in the bed of the river at Conklingville, rock 

 was not struck within two hundred feet. If the channel is thus 

 drift filled it clearly means that the rock channel was cut prior to 

 the last ice invasion. This seems to imply at least one earlier 

 advance and retreat of the ice over the region since it is pretty cer- 



1 See paper by writer entitled Preglacial Course of the Upper Hudson 

 River, in Geol. Soc. Am. Bui. 22:177-86. 



