60 



GEOLOGY OF OHIO. 



arm of the Lake, into which the ridges were deflected on the west side, 

 where the slope was gentle and the material soft. On the east side the 

 waves raised by westerly winds cut terraces at corresponding elevations. 

 The valley of Rocky river, near its mouth, is a narrow gorge of quite re- 

 cent date, and the manner in which the ridges terminate on its margins 

 show that it had no existence when they were traced on the surface ; 

 hence we are justified in concluding that all the rock-cutting of the 

 Rocky river gorge has been done since the ridges were formed. The 

 fact that the lower ridge runs directly across the delta plain at the 

 mouth of the Cuyahoga proves not only that the valley was filled to 

 this point when the ridge was formed, but since this ridge is here un- 

 derlaid by about 300 feet of Drift deposits, the upper part consisting of 

 fine laminated clays and stratified sand and gravel, that glaciers could have 

 had no agency in its formation. The succession of beaches on the west 

 side, and the terraces east of the valley at Cleveland, are shown in sub- 

 joined wood-cuts. 



, PROFILE SECTION OF LAKE RIDGES, CLEVELAND, WEST SIDE. 



1. Sand, gravel, and clay. 2. Erie clay, laminated. 3. Erie Bhale. A A. Bowlders. 



Terraces East of Cleveland. 



i. First Terrace, 165 feet above the Lake. 



*. Second Terrace, 210 feet above the Lake. 



3. Drift deposits forming the old Delta of the Cuyahoga and filling the old valley. 



East of Cleveland the lake ridges continue into Pennsylvania and 

 western New York, and probably connect with the series observed on the 

 south shore of Lake Ontario; for when the water stood at the level of 

 the lowest of the ridges of Lake Erie, they overtopped the divide which 

 separates Lake Erie from Lake Ontario. In the counties of Lake and 

 Ashtabula two distinct ridges are usually traceable, and sometimes one 



