480 J. W. SPENCER PRE-GLACIAL HANGING VALLEYS 



Cayuga Lake^ or of the northward warping of the earth's crust in that 

 region, which show that Cayuga Lake is not rock basin. 



Hanging Valley op Taughannock Falls 



I visited Taughannock Falls, in the most important hanging valley 

 adjacent to Cayuga Lake. The gorge is excavated out of the jointed 

 Devonian shales favorable for the production of vertical walls. Imme- 

 diately north of this stream is a partly reopened buried valley, described 

 by Prof. James Hall in 1842. It is plain that this was the course of the 

 ancient drainage of the plateau, which becoming obstructed during the 

 glacial period was diverted to the present course of Taughannock Falls. 



Eeversals of Drainage at the Head of Seneca Valley and its 



Excavation 



Seneca Lake is even more interesting. In ascending the valley from 

 the lake to the summit, at Horseheads (from 443 to 914 feet above the 

 sea), a deep valley (more than 158 feet) has been found by borings. At 

 Horseheads these do not reach to bedrock, but show the valley floor to be 

 less than 756 feet above tide. If only 75 feet of the drift filling were 

 removed (at A-B on figure 1) the Chemung Eiver, with the Cohocton, 

 would be turned northeastward in a broad valley and discharge through 

 Seneca Lake, while the present course is along a narrow rock-bound 

 channel to the Susquehanna. Originally the Cohocton and other strfeams 

 flowed southward at a high level, but in the early history of the Seneca 

 Valley the north-bound waters encroached on the plateau and robbed the 

 south-flowing streams. Then the drainage through Seneca Valley was in- 

 creased 12 or 15 fold, with a deep channel developing more rapidly than 

 the hill on either side could be worn down by their restricted drainage. 

 With the deposits of the glacial period a barrier was formed which turned 

 the Chemung and associated streams southward from Seneca Valley. 



A word may be added with regard to Seneca Lake. The deepest sound- 

 ing is 612 feet, but a boring at the head of the lake was said to reach 

 1,000 feet below the surface. This well has been cited as the evidence of 

 the depth of the drift. Concerning it, Mr. John Clute, the manager of 

 the salt company, who caused the boring to be made, stated to me that 

 it was in quicksand, but no detailed record or samples were kept. The 

 salt wells on the side of the valley require to be cased to a depth of 1,100 

 feet on account of the character of the rock. These facts throw doubt 

 on the reported depth of the drift found in the well. 



