4'^4 GEOLOGY 01' OHIO. 



of the blue clay, were exposed by a slowly advancing 

 submergence to the action of waves or currents, it is easy to see that its 

 clay, sand and gravel would be assorted aad separated. The coarser 

 materials would be moved the least distance and the finer clays the 

 greatest distance from their original beds. As the submergence was 

 gradually extended, then we ought to find beds of gravel overlying the 

 blue clay, themselves overlain by sand, and finally covered with the 

 finest grained clays. Such is precisely the general order of the arrange- 

 ment in all of these districts. We ought furthermore to expsct that on 

 the highest grounds of the county beds of gravel and sand would abound. 

 This also is exactly the case. Ohlinger's Hill, as high a point as is con- 

 tained in the county, is tho resort of the whole country fir miles around, 

 for plastering sand, extensive deposits of which occupy the highest parts 

 of the dividing ridge. 



The same line of facts is met with on the high ground west of London, 

 a ridge scarcely inferior in ele /atioa to the one already referred to. It 

 is, in fact, a part of the same water-shed — separating the drainage of the 

 Scioto from that of the Little Miami. Almost the whole of this region 

 is occupied with heavy beds of well-washed gravel. The whole supply 

 for London and its vicinity is derived fiom this locality. It nra=;t, however, 

 be noted that these high grounds also contain remnants of the old glacial 

 clays, which furnish, a-> at Ohlinger's Hill, a soil of entirely different 

 properties from any other s )il3 in the county. The difference li'-s in the 

 fact that the high location of the masses his prevented the accumula- 

 tion of vegetable matter in them. They produce fruit well and are good 

 wheat lands when properly treated, but they are decidedly inferior as 

 grass-lands to the rest of the county. In fact, but a thin sod establishes 

 itself upon them unless special care is taken to secure this result. 



The submorgence of this district and the consequences resulting from 

 such a fact have b»en spoken of. It is easy to see that the emergence which 

 converted it into dry land again, mu't have been attended with equally 

 marked results. As drainage systems began to be established or re-estab- 

 lished, the accumulations of clay, sand and gravel of there-arranged drift 

 would often be withdrawn from the surface over which they had been 

 distributed, and the broad valleys thron'^jh which currents were moving, 

 would be sure to receive them. The bowlder clay would thus be exposed 

 on portions of these areas. 



The northern and central districts of the county contain almost all of 

 the exposures of this sort, while the southern tiers of townsliips which 

 lie a hundred feet or thereabouts lower than the above named districts, 

 bold by far the most gravel. 



