Ti6 Frank Carney 



influence on the direction of the ri\-er. as the development of the 

 highest Warren beach here was sufficient to turn the course of the 

 streani to the west about one-lialf mile. 



It is evident that Black river had a falls over the Berea sand- 

 stone a short distance north of the point where the two branches 

 now meet. Since that time the falls have moved up-stream not much 

 over a mile. North of the outcropping Berea the river has had 

 easy work in the shale; it has developed many small tributaries con- 

 sidering the small area drained. 



In the region south of Avon Center only one stream, the head- 

 Avater part of French creek, appeared after the Whittlesey decline ; 

 this flowed into the lake near Avon. The drainage from the area 

 north of Butternut Ridge escaped across the Whittlesey beach, 

 thence to the Black river. Different segments of this stream show 

 the directive influence of beach ridges. 



West of the Black river the two beaches are so close together 

 that few streams developed save continuations of those that were 

 already tributary to Lake Whittlesey ; these were lengthened usually 

 by one mile, the average distance between the two beaches. Beaver 

 creek, however, responded most successfully to the added 60 feet in 

 gradient ; south of North Amherst it has made much progress in 

 valley development, considering the resistant rock in which it is 

 working. 



Lake Erie hase-level. — Lake W^arren dropped about 95 feet in 

 establishing this new base-level. The added drainage territory is 

 entirely in shale, with a very slight \'eneer of glacial drift. This 

 easily eroded rock has given the streams which cross it an appear- 

 ance of greater age than these same streams show in the much older 

 parts of their course. Bodi Black river and Beaver creek have de- 

 veloped relatively wide valleys, which they are still broadening by 

 lateral erosion. These two streams control so completely the drain- 

 age territory south tliat the shore of Lake Erie is creased by only a 

 couple of Other creeks that have as yet accomplished much erosion. 

 Two slight streams near Beach Park have cut the shales back, de- 

 veloping youthful valleys, ^^'est of Black river, Martin run has 

 made a longer and slightly wider \alley. 



Sinnuiary. — 'In the northern fourteen miles of its course. Black 

 river has been sul)ject to four base-levels. W'q have no data for 

 satisfactorily measuring their re]ati\'e time periods. The Berea 



