G. F. Wright — Continuity of 'the Glacial Period. 175 



Clearly the explanation is that before the deposition of the 

 gravel in the ox-bow the rock erosion had proceeded till it had 

 produced essentially the present topographical conditions. 

 The gorge of the Allegheny was then refilled with Glacial 

 gravel till it reached the summit of the 1100-foot terrace upon 

 the western side, and partially filled in the ox-bow across the 

 outlet of both its prongs. Naturally the work proceeded fast- 

 est in the upper prong, and the terrace was gradually built out 

 till it reached the point A. Naturally, also, there would be no 

 such extensive pushing of material up the lower prong ; so that 

 we find across it simply a gravel terrace corresponding to other 

 terraces upon that side of the river. The continuance of the 

 Gacial floods at that level was not sufficiently long to permit 

 the deposition which had taken place in the upper prong to 

 extend around the whole circuit of the loop. Evidently the 

 depositing Glacial flood after attaining its maximum height 

 retreated with comparative rapidity, — a rapidity which is not 

 at all consonant with the theory that it was compelled to lower 

 its bed through a rock bottom ; nor does the general appear- 

 ance of the high-level gravel deposit, either here or elsewhere, 

 indicate such an enormous age as Professor Chamberlin's 

 theory would imply. There is everywhere against this theory 

 the relatively small amount of erosion which had taken place 

 in the gravel since the deposition. 



The second case upon which I will stop briefly to comment 

 is at Kennerdell, which is situated upon a point of a long ox- 

 bow occupied by the present river. Here the gravel with 

 Glacial pebbles constitutes a continuous blanket up the slope 

 from the river to a height of something over 300 feet. TJp 

 both of the roads branching off from the station, and reaching 

 the summit on either side of the ox-bow, this deposit of gravel 

 is continuous, and contains Archaean pebbles nearly up to the 

 height above mentioned. The theory that this blanket of 

 gravel (how thick it is I did not have time to ascertain, for 

 the rock nowhere appeared along the roads) is simply a rem- 

 nant that has survived the long period during which the whole 

 rock gorge was eroded, and which has gradually slid down from 

 the summit or been re-deposited as the shelf was undercut, I 

 think few people who examine it will entertain. On the other 

 hand, it is not difficult to understand how it might be left in 

 the process of a re-erosion of the trough after it had been 

 filled with loose material. 



The conclusion to which all these facts point with convinc- 

 ing force is that, after along period of base-levelling in the Ter- 

 tiary era, during which the 200-foot rock shelves formed a por- 

 tion of the bottom of the stream, there came on a continental 

 elevation which permitted the streams rapidly to cut narrow, 



