of the Northern Catskill Mountains. 147 



due, like Grand Gorge, to cutting by glacial streams. The 

 movement of the glaciers round the mountains produced con- 

 ditions which would naturally lead to the formation of some 

 such notches, for, as will be shown on a subsequent page, two 

 great glacial lobes were pushing into this region from nearly 

 opposite directions : — one, moving down the Hudson Valley 

 and pushing into the upper Schoharie Valley from the east,* 

 would effectively block drainage in that direction ; while the 

 other moving up Schoharie Valley from the north must 

 have closed that outlet and forced the water to find a passage 

 to the south across the range. 



Glacial Geology. 

 Direction of ice movement as indicated by striae. 



Observations of striae are uot very numerous, but they are 

 sufficient to indicate certain broader features of the glacial 

 movement (fig. 6). On the hill just north of Hobart, striae 

 point nearly due south. At the head of Trout Brook also the 

 striae point south. On the hill one mile west of Stamford 

 village the direction is a little east of south. These localities, 

 all on the 2000 ft. plateau to the west of the termination of 

 the Central Escarpment at Potter Hill, accord closely with 

 each other and agree in indicating a general north-south move- 

 ment of the ice here. 



On the north and east sides of the Central Escarpment, how- 

 ever, in the drainage basin of Schoharie Creek, the striae 

 indicate that a lobe of ice lay over Schoharie Valley and 

 that it spread out fan-like north of the Catskills, and even 

 pushed over some of the higher passes through the escarpment. 

 Thus, where the road crosses the divide a mile northwest of 

 Mayham Pond at 2100 feet, striae point almost due southwest. 

 At an elevation of nearly 3000 feet in a pass through the 

 Central Escarpment three quarters of a mile north of McGregor 

 Mountain the direction is also about southwest — varying some- 

 what with the topography from southwest to about S. 40 W. On 

 the hill north of Grand Gorge Station at 1800 feet, the striae point 

 S. about 25° W. and a mile farther north, across the railroad, the 

 direction is nearly the same. (It is remarkable that the direc- 

 tion of the striae near the Grand Gorge Station does not seem 

 to be influenced by the Grand Gorge gap. They point, not 

 toward the gap, but toward the eastern slope of Irish Moun- 

 tain, as if at the time the striae were made the ice was overrid- 

 ing the whole range.) Across Schoharie Creek at 1800 feet 

 on the extreme south point of Darling Hill (2 miles north- 

 northeast of Gilboa, Gilboa sheet) the striae point about 20 



* Ramsay, A. C, Quart. Jour. Geol. Soc, London, xv, 208-09, 1859. 



