216 GLACIAL FOEMATIONS OF ERIE AND OHIO BASINS. 



enters a preglacial channel wliich has been filled to a depth of about 200 

 feet with drift. This old valley can scarcely have drained a large area, 

 since the larger systems discharging through the Grand River Basin and 

 the Cuyahoga would have absorbed nearly all the drainage except a narrow 

 strip lying between their trunk streams. 



CUYAHOGA RIVEE. 



The present Cuyahoga River has its head near the source of the East 

 Fork of Chagrin River, on the uplands east of the Grand River Basin, only 

 a few miles from the shore of Lake Erie. It leads southwestward for nearly 

 50 miles, away from the lake, occupying a shallow valley bordered by 

 marshes throughout much of its course, and having an average fall of but 

 4.5 feet per mile. At the village of Cuyahoga Falls it makes a fall of 220 

 feet within a distance of 3 miles and enters a preglacial valley, which it 

 follows northward to Lake Erie at Cleveland. 



In this preglacial valley there is a heavy drift filling, both beneath the 

 stream and on the borders of the valley Wells in Cleveland indicate that 

 the valley floor is about 400 feet below the mouth of the present streani, or 

 less than 200 feet above tide. Silt deposits on the borders of the valley 

 indicate that it was filled to a height of fully 200 feet above the present 

 stream, or to within 100 feet of the level of the bordering uplands. From 

 these data it appears that the preglacial valley • was about 700 feet in 

 depth. Its width is scarcely 2 miles at the level of the present stream, and 

 is probably much narrower at the level of the rock floor. Being bordered 

 at the brow of the bluffs by ledges of resistant sandstone, it has preserved 

 a somewhat narrow channel. 



The preglacial valley occupied by the Cuyahoga in its lower course 

 may have constituted the line of discharge for much of the region now 

 tributary to Tuscarawas River, as indicated in the discussion of that drain- 

 age system (pp. 165-168). 



ROCKY RIVER. 



Rocky River has two forks, which unite near the town of Berea, Ohio. 

 These tributaries are mainly in drift-filled preglacial valleys, but the 

 united stream northward from Berea is largely in a new course. It crosses 

 the preglacial valley from west to east a short distance north of this city, 

 as pointed out by Dr. D. T. Grould,^ who has traced a preglacial valley 



^The Berea Advertiser, April 16, 1886. 



