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G. F. WRIGHT POSTGLACIAL EROSION AND OXIDATION 



"There is one thing I have tried to keep in mind, and that is that the Alle- 

 ghany deposits are the remainders of the sediments deposited before the ice 

 reached that river, as modified by the actual presence of the ice. which prob- 

 ably did no work in the valley bottoms, owing to the great depth and buoyancy 

 of the water and as further changed by the action of the retreating glacier. 



"In every case of an abnormal form or situation of a deposit I have tried to 

 imagine how the forces must have acted, and the first thing was to get the 



Figure 2. — Map of the Vicinity of Warren, Pennsylvania 



depth of water and direction of flow. At one time there were two forces act- 

 ing near Warren in opposite directions — the first, from upstream, filling in the 

 north end of the valley; the second, from the Brokenstraw, filling the other end. 

 These met about half way between Warren and Irvineton. At that time I 

 think the col which formed the highest water and made a flow past Clarendon 

 had not been degraded, but after it had been cut down there began the action 

 of the forces that finally made the present Alleghany Valley. 



