ANCIENT GORGE OF BEAVER RIVER. 459 



The gorge is completely filled with drift material for more than sixty feet 

 ot its depth at the river mouth, while at Lawrence Junction there is nearly 

 or quite two hundred feet of such filling. One of the writers of this paper 

 has elsewhere* presented facts to prove that in preglacial times the stream 

 occupying this deep and now partially filled canon flowed toward the north 

 and was tributary to the Erian river of Spencer, which then occupied the 

 central valley in the present basin of Lake Erie. Thus the Beaver river 

 exhibits the phenomena of reversed drainage, and conforms to the system of 

 reversed drainage worked out by Professor John F. Carll in the upper 

 Allegheny region of Pennsylvania. 



Wherever the distance between the walls of the rock gorge-is sufficient to 

 have preserved them from stream erosion, we find the Pleistocene terraces cov- 

 ering the walls to a greater or less height. They are best developed for the 

 first two or three miles of the river's course above the terminal moraine ; 

 also on the parent streams for a considerable distance, and more especially 

 for the last five miles of its course. The intervening portion is so narrowly 

 inclosed that the terraces have for the most part been entirely removed by 

 erosion, only fragments remaining. 



The Glacial Phenomena. 



Glacial Deposits. — In the vicinity of Wampum (five miles from the head 

 of Beaver river and immediately across from Chewton, mentioned below) the 

 terminal moraine has been described by Lewis and Wright f as crossing the 

 river. From their report we extract the following description of the point 

 of crossing : 



" The Beaver river is crossed by the moraine at Chewton, eight miles south of 

 Newcastle, and is here filled with immense accumulations of stratified drift several 

 miles in length. Chewton stands upon a high and broad terrace more than 150 feet 

 deep, which forms a level plain at its southern termination, but which develops north- 

 ward into ridges and conical hills, inclosing large kettle-holes and having all the typical 

 features of a glacial deposit. This conspicuous accumulation extends for nearly two 

 miles up the river, and is heaped up into still higher knolls and ridges as the river is 

 ascended. It passes into till upon the higher ground on each side of the river. While 

 the water issuing from under the glacier, in this river valley has stratified the mate- 

 rials of the moraine and, with the aid of ice, has heaped up the sand and gravel into 

 the peculiar knolls and ridges so characteristic of a glacial region, no evidence ap- 

 pears that the glacier extended any tongue of ice down the river. There is no sign 

 of drift deposits in the valley of the Beaver south of the moraine other than those 

 formed by the action of water." 



The terrace 150 feet in depth, mentioned in the above quotation as under- 

 lying the village of Chewton, is the old base-level plain (as is clearly seen 



*P. M. Foshay, Am. Journ. Sci., vol. XL, 1890, p. 397. 



t Report Z, Second Geol. Survey of Pennsylvania, by H. C. Lewis and G. F. Wright, 1884, p. 194. 



