GEOLOGY OF THE PARADOX LAKE QUADRANGLE 477 



glacial lake, the lower Trout brook has reestablished itself in this 

 old valley and has beheaded upper Trout brook whose former course 

 was eastward, over hard gneisses. 



Horicon and Schroon. Pharaoh lake and Wolf and Whortleberry 

 ponds lie in rock basins caused by faulting. The outlets of Pharaoh 

 lake and of Whortleberry pond join, and together are combined with 

 Desolate brook. The junction of these three streams takes place 

 in a broad valley filled with stratified drift. 



Desolate brook is now a swamp or '' vly," its still waters having 

 been filled with sphagnum and other vegetation. The trail mapped 

 is now impassable owing- to the increasing swampy conditions. 



At the northern end of Schroon lake is a wide flat extending 

 northward for about three miles. This flat appears to be a glacial 

 delta. At present the Schroon river meanders over its surface, and 

 the greater portion of the flat is swampy. 



Schroon and North Hudson. The Schroon river in its south- 

 westerly course extends for about five miles within the limits of 

 the quadrangle. On its banks are well-developed terraces. 



In the course of these five miles the river descends 50 feet. Its 

 most conspicuous terrace drops from 960 feet in the north to 930 

 in the south — 30 foot fall in the same distance in which the present 

 river falls 50 feet. 



The surface of this terrace is slightly uneven and suggests an 

 origin as a kame terrace, while the ice still stood in the valley. The 

 front of this terrace has been extensively eroded, in part by the 

 Schroon river, which has built a lower terrace of flood plain origin, 

 and in sO' doing has worn back the face of the older one ; in part by 

 recent gullying. Gullies once started grow with astonishing rapid- 

 ity, houses and the highways being frequently undermined. The 

 material of this terrace is sand. 



A higher terrace is to be distinguished at a few localities. This 

 higher terrace is partly built, partly cut. It occurs 35 feet above 

 the main terrace. Through the Schroon valley sand dunes abound, 

 the material loosened along the gullies being blown by the wind 

 and deposited on either of the two lower levels. 



The main terrace of the Schroon extends up its tributary, Black 

 brook. 



