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NEW YORK STATE MUSEUM 



of stratified drift. The upper course of the present stream is super- 

 imposed over this drift-covering and wanders considerably, having 

 developed a broad flood plain in its upper course. No evidence was 

 found of a glacial lake in this locality, the evidence pointing towards 

 the filling of the valley by drift deposited by the escaping floods 

 from the melting ice. Rock first appears at the bridge (one inch 

 from the eastern end of the map) and downstream from this point 

 the course alternates between quiet reaches, where the stream flows 

 over drift or along the strike of the gneiss, and little cascades and 

 rapids, where it flows southward down the dip. At the largest fall 

 trfe Hague gristmill is situated, the fall in this case resulting partly 

 from a soft, easily eroded shear-zone in the gneiss at the base of 

 the • present fall. Below this fall the stream bed is full of loose 

 material, in part at least of postglacial origin and resulting from the 

 cutting back near the fall. A similar fall occurs at the corner of 

 the map. 



Potholes are found at these falls, and at the one at the gristmill 

 a little lake has been formed part way down the fall from the 

 wearing away of a soft layer [pi. 8, fig. i]. 



Trout brook also flows through an old drift-filled valley, slowly 

 meandering in its upper course, and alternating between quiet 

 reaches and rapids, according to whether its drift cover is or is not 

 cut through. The rock here being massive, no such changes can be 

 seen as in the southern brook. Close to the edge. of the map Trout 

 brook reaches the Potsdam sandstone and turns abruptly northward. 

 It leaves an open valley only three fourths of a mile in length which 

 leads east straight to Lake George, and turns abruptly northeast, 

 emptying into Lake Champlain six miles away. Its lower course is 

 on the Ticonderoga quadrangle. 



This northeastward bearing valley is a very old one. Small ex- 

 posures of limestone indicate that it was originally excavated upon 

 a limestone fold. The Potsdam sandstone lies undisturbed in three 

 localities on its lower course, suggesting that the valley existed in 

 Cambric time and that it was drowned by the Potsdam sea. In 

 Champlain time the valley was occupied by the water, probably of an 

 arm of Lake Hudson-Champlain. Since the shrinkage of this 



