GEOLOGY OF THE PORT LEYDEN QUADRANGLE 45 



even the hardest rocks, exposed during all of postglacial- time, 

 have been weathered enough to cause an obliteration of the glacial 

 marks. 



Striae pointing from s. 25° to 40° e. have been located as follows : 



g and also Ys 



On Trenton limestone i mile south of Martinsbure and also I 



mile to the east of that village (s. 25° e.) ; on Black River lime- 

 stone just west of Lyons Falls ; on Precambric near the 

 mouth of Roaring brook, i^ miles northeast-north of Glenfield and 

 also ys mile southwest and 34 mile southeast-south of the same vil- 

 lage; on Precambric i mile northeast of Denley and ^ mile north- 

 east of Hawkinsville. Striae bearing nearly south occur on the Pre- 

 cambric I mile east of Port Leyden. The southeasterly movement, 

 shown by these marks, changed to a more nearly easterly move- 

 ment in the Mohawk valley region, and this is just what would be 

 expected according to the statement of Chamberlin. It should be 

 noted that the Black river valley, which is the chief topographic 

 feature on the western side of the Adirondacks, had much to do 

 with determining the direction of flow of the ice. This valley 

 existed in preglacial time and the close parallelism between the 

 directions of the striae and the direction of the valley shows the 

 influence of the latter in determining the ice movement. Along the 

 northwestern border of the Adirondacks the ice undoubtedly moved 

 southwestwardly. xA^long the eastern border of the Adirondacks 

 the general southerly movement of the ice has been well established, 

 as has also the westerly movement up the Mohawk valley toward 

 Little Falls. Thus the statement of Chamberlin, regarding ice flow 

 around the Adirondacks, harmonizes almost perfectly with the 

 observed striae. 



But the question still arises, what was the direction of the current 

 during the hight of glaciation? We have abundant evidence to 

 prove that, during the hight of glaciation, the main current was a 

 southeasterly one. On the Long Lake quadrangle in the midst of 

 the Adirondacks Professor Gushing has recorded a number of stfiae 

 all of which point toward the southwest.^ Over the region south of 

 the Adirondacks and the Mohawk valley the observations of both 

 Brigham^ and Chamberlin^ show that the ice moved in a general 

 southwesterly direction. Another strong evidence favoring the 

 southwesterly current is the distribution of glacial boulders over the 



' N. Y. State Mus. Bui. 115. 1906. p. 495. 

 ' Amer. Jour. Sci. 1895. 49:216. 

 'loc. cit. p. 365. 



