LORAIN COUNTY. 209 



county is immediately underlain by beds of clay, which form part of the 

 series of Drift deposits that cover so much of Ohio and the adjoining 

 States. Beneath these the surface of the underlying rocks— wherever 

 hard enough to retain such markings — is found planed, grooved, and 

 striated, evidently by ice which formed part of a great glacier that rilled 

 the lake basin and flowed over it, reaching as far as the Ohio. This 

 glacier was for ages moving from the north southward, and as it rested 

 with immense weight on the rocky sub-strata of the country, by the aid 

 of sand and gravel which accumulated beneath it, it ground down the 

 rocks over which it moved to nearly a plane surface, and grooved 

 and scratched them just as glaciers now do the rocks which they 

 traverse. The materials excavated and ground up by the ice-sheet were 

 pushed along by it in its motion and thrust out at its margin, where 

 they remained to form a "moraine," or were washed away by the water 

 formed by the melting ice. Hence it is apparent that no considerable 

 accumulation of matter of any kind could take place under the gla- 

 cier. But we find the glaciated surface often deeply buried under beds 

 of clay, sand, and gravel, which must have been deposited there after 

 the retreat of the glacier. These sheets of superficial material are called 

 the " Drift," from the fact that they have b -en generally transported 

 long distances from their place of origin. In the northern part of Ohio 

 the Drift deposits are usually clay — stratified or unstratified — with more 

 or less sand and gravel, and at the surface large transported bowlders. 

 Of this series the lowest is unstratified clay, thickly set with frag- 

 ments of shale, and with some small, usually striated, bowlders of crys- 

 talline rock, brought from the region north of the lakes. This deposit 

 is called the bowlder clay, and is the direct product of the grinding 

 action of the glaciers upon the shales, limestones, etc., which have been 

 excavated in the formation of the lake basin. As the glacier melted 

 away and retreated northward, this bowlder clay was left in a somewhat 

 irregular sheet along its margin, and we still find it covering the rock 

 surfaces over most of Lorain county, where a basin of water took the 

 place of the ice. Prom this were deposited sheets of fine clay, frequently 

 beautifully stratified, and without pebbles or bowlders. Hence we often 

 find the lower bowlder clay overlaid by laminated clay, but the two 

 varieties blend together and have been included in the general term 

 "Erie Clay." The bowlder clay is also frequently called hard-pan. It is 

 blue in color, and exceedingly compact and tough. Sometimes it is yel- 

 low or reddish, from the oxidation of the iron it contains ; and this is the 

 prevailing color of the stratified clay. 

 The sand and gravel which sometimes overlie the clays were deposited 



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