42 



GEOLOGY OF OHIO. 



resemble them are in the lines of the old waste-weirs, through which 

 the surplus water flowed from the lake-basin to the Ohio. In the Miami 

 Valley are hills of well-rounded gravel, not unlike the Karnes in general 

 character, but they are mostly composed of lipiestone pebbles derived 

 from the upper portion of the valley, and are remnants of sheets of val- 

 ley-drift, eroded by the present streams. 



That the kames of the water-shed have been formed by the action of 

 water on the morainic material of the Erie clay, seems certain, but how 

 the necessary floods of water could be produced there, is a difiicult problem. 

 Up to the present time no more plausible explanatory hypotheses than 

 those mentioned have suggested themselves. 



ICEBEEG DRIFT. 



Most recent writers on the surface geology of North America, have 

 given to icebergs a more or lees prominent part in the distribution of the 

 Drift material. By some they are made the chief agent, both in the 

 scoring of the rocks and in the transportation of clay, sand, gravel, and 

 bowlders, but we have shown that both the erosion and transportation 

 were chiefly affected by glaciers. Another party has denied altogether 

 the agency of icebergs in producing the phenomena of the Drift. Promi- 

 nent among the latter is Prof. N. H. Winchell, who has written volumi- 

 nously on the Drift deposits, particularly those of the north-west. He 

 attributes all the phenomena of the Drift to glaciers, denies the littoral 

 origin of the so-called beaches of the lake basin, considering them mo- 

 raines, and intimates that the four hundred feet beach, near Montreal, 

 may come into the same category.* Every unprejudiced person must, 

 however, admit, from the facts given in our second volume, that icebergs 

 did at one time float over the waters that filled the lake basin, transport- 

 ing and depositing more or less of the material now found on the surface 

 of Ohio. Several instances of the occurrence of large striated bowlders, 

 buried in laminated clays, where they must have been floated and dropped 

 from an ice-raft, are referred to in Chapter XXX. Another instance which 

 has recently come under the observation of the writer, is equally conclu- 

 siv9' of the presence of icebergs in the lake basin. In cutting down the 

 cliff of clay on the lake shore, near the Union Depot, at Cleveland, in 

 1876, a large striated bowlder of gneiss was found bedded in the finely 

 laminated clay, (the upper and stratified portion of the Erie clay), some 

 twenty feet below its surface and forty feet above the lake. That this 

 stone had come from the Canadian highlands, had once been imbedded 

 in an ice- raft, and was dropped into the clay that was being deposited at 

 the bottom of the lake, when its surface was very much higher than now 



' Drift J)epoait3 of the North-west, Popular Science Monthly, July, 1873, p. 819. 



