304 R. R. HICE — NORTHWARD FLOW OF ANCIENT BEAVER RIVER 



while the rising of the strata to the northward brought up the underly- 

 ing, softer formations and exposed them to stream work. The pot-holes 

 indicate a rapid current at this point, which could have been the case 

 only by the cutting away of the underlying strata northward. This im- 

 plies that part of the erosion of the wide " inner " valley north of Wam- 

 pum, heretofore regarded as the work of the south-flowing stream alone, 

 occurred before the time of reversal. The amount of such erosion we 

 do not yet know. I have heretofore called attention to some rock benches 

 near Moravia,* about 4 miles northward, at a much lower elevation, re- 

 ferring to them as remnants left in the cutting by the south-flowing 

 stream. They may, however, in the light of the evidence of these pot- 

 holes that the stream here fell rapidl3^ prove to belong to the system of 

 the old north-flowing stream. They are higher above the stream than 

 some remnants left by the south-flowing stream nearer the mouth of the 

 Beaver, and if they prove to belong to the north-flowing stream, they 

 will easily harmonize with the level of the old floor a few miles to the 

 northward, which is 810 feet, as reported by Leverett.f 



From Pittsburg to these pot-holes, a distance of almost 40 miles, the 

 fall is practically nothing, but here there seems to be a sharp decline of 

 some 80 feet in a few miles. There is no difl'erential elevation to account 

 for this great difference in the rate of fall, but these pot-holes seem to 

 suggest that here there were at least rapids and perhaps a fall of some 

 80 feet in the old north-flowing stream at a time preceding the Kansan 

 stage of glaciation. 



*Am. Jour. Sei., xlix, p. 116. 



tU. S. Geol. Survey Mon. xli, p. 152. 



