74 NEW YORK STATE MUSEUM 



valleys, the • rate of retreat was slow and moraines were formed ; 

 but in the narrow valleys the melting of an equal amount of ice 

 would produce a much more rapid recession, giving but little oppor- 

 tunity for the deposition of material. Again at the northeastern 

 ends of the passes the ice-tongues paused long enough to deposit 

 another series of moraines. 



The damming of such valleys by recessional moraines has resulted 

 in the Cascade lakes, located in the Mt Marcy sheet; and in Silver 

 lake and Taylor pond on the northern edge of the Lake Placid 

 quadrangle. A very striking example of morainal damming is Lake 

 Placid, formed by the blockading of two parallel (fault-line?) 

 valleys which have been joined by valleys, producing the islands, 

 thus forming a ladder-shaped body of water. In a depression in 

 the dam Mirror lake now lies. Just south of Mirror lake Doctor 

 Miller found, beside the road, an exposure 20 feet thick, which 

 showed glacial till with large boulders in the upper half resting 

 upon distinctly stratified sands. ^ The writer would infer that dur- 

 ing slight variations in the advance and retreat of the ice lobe, 

 glacial debris was deposited on top of a glacial lake bottom (see 

 page 83. Glacial Lake Upper Newman). A similar phenomenon is 

 known in the Cobb's hill kame-moraine at Rochester, N. Y. 



The preglacial drainage has been modified by glacial material of 

 one kind or another in several localities. A good example was 

 found south of the town of Keene in the East branch of the Ausable 

 river. In this comparatively broad valley on the northern edge of 

 the Mt Marcy sheet we note an unnamed hill, around the two sides 

 of which the two highways leading to Keene Valley circle. To 

 the west oi this hill the present river rushes between steep walls 

 of syenite and mixed rocks (southern edge of the Lake Placid 

 quadrangle), experiencing rapids and falls. It is clearly a post- 

 glacial channel and is one of the beauty spots in the quadrangle. 

 On the other side of this hill the preglacial channel is plainly per- 

 ceptible, although now blocked by sands of a lateral delta." 



Local Moraines; Local Glaciation 



The writer's work in the central Adirondacks would lead him to 

 suspect that local glaciers existed on the slopes of the higher moun- 

 tains. This conclusion has been reached through the study of 



* Miller, W. J., Personal communication, Jan. 17, 1917. 



^ Ailing-, H. L., Glacial Geology of the A'lt Marcy Quadrangle, in The 

 Geology of the Mt Marcy Quadrangle, Kemp, J. F., in preparation; N. Y. 

 State Mus. Bui. 



