48 NEW YORK STATE MUSEUM 



is true in the Luzerne quadrangle. In some cases striae and glaci- 

 ated ledges have been observed several thousand feet above sea 

 level, the highest which happened to be noted in the Luzerne quad- 

 rangle being 1300 to 1500 feet. Adirondack glacial lakes at alti- 

 tudes of several thousand feet above sea level also bear strong testi- 

 mony to great depth of ice. Several lakes and ponds of the 

 Luzerne quadrangle lie at altitudes of from 1200 to 1600 feet. 



The general direction of movement of the ice across the Adiron- 

 dacks was toward the south and southwest, with comparatively few 

 local exceptions. Such a persistent direction of movement also 

 strongly argues for complete burial of the whole region under the 

 ice. The ice spread southward as a part of the great Labradorean 

 ice sheet of Canada. When the ice, early in its southward move- 

 ment, struck the Adirondack highland district, one portion flowed 

 southward through the Champlain valley and sent a branch lobe 

 westward into the Mohawk valley. At the same time another por- 

 tion flowed around the western side of the mountains and sent a 

 lobe eastward into the Mohawk valley. The two lobes, one from 

 the east and the other from the west, met in the central Mohawk 

 valley, leaving the main portion of the Adirondacks free from ice. 

 But, as the ice increased in volume, more and more of the Adiron- 

 dack region was covered until finally even the highest points were 

 buried. During the retreat of the ice the higher east-central Adi- 

 rondack region was the first to be freed from the ice, and the ice- 

 freed portion gradually increased in size. A wonderful succession 

 of glacial lakes, some of them very large, developed during the 

 retreat of the vast glacier from northern New York. 



Direction of Ice Movement across the Quadrangle 



Distinct glacial scratches (striae), indicating the direction of 

 movement of the ice across the Luzerne quadrangle, were observed 

 at fourteen places, the location and bearing of each being indicated 

 on the geologic map. They are as follows : 



1 North-south. On Grenville gneiss by the road two-thirds of 

 a mile west of Number Nine pond. 



2 North-south. On Grenville gneiss by the road one-half of a 

 mile northwest of Athol. 



3 North-south. On Grenville-granite mixed rocks by the rail- 

 road I mile northeast of Thurman station. 



4 South 5 degrees west. On granite by the road at the map 

 limit I mile northeast of the summit of Black Spruce mountain. 



