SURFACE GEOLOGY. 



Buried Channel of Mad River, at Springfield, 



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Horizontal Scale, 2 inches to 1 mile. 

 Vertical Scale, 1 inch to 200 feet. 



The valleys of the rivers which run into Lake Erie have frequently 

 been bored for oil, and these explorations have revealed the fact that 

 some of these streams once flowed more than 200 feet below the level at 

 which they now enter the lake. For example : borings at Toledo show 

 that the old bed of the Maumee is at least 140 feet below its present sur- 

 face level. In the valley of the Cuyahoga many borings have been made, 

 nearly all of which show a great depth of clay, sand, and gravel above 

 the rocky bottom of the valley. Of these, one, situated in the city of 

 Cleveland, passed through clay and sand to the depth of 238 feet before 

 reaching the rock. In this case the well head is about ten feet above the 

 lake-level. We, therefore, have evidence that at this point the rocky 

 bottom of the Cuyahoga lies 228 feet below the surface of the Lake. In 



