276 GEOLOGY OF OHIO. 



This list may be increased by adding Gymnocladus Canadensis, Lam. 

 (Kentucky coffee-tree), seen in Kadnor township, and Prunus Americana, 

 Marshall. The red mulberry {Moms rubra, L.) is rather common, growing 

 ' in situations that prove it indigenous to the county. It is also common, 

 in its native state, in most of north-western Ohio. The Balm of Gilead 

 (Populus candicans, Ait.) and the common locust (Robinia pseudacacia L.) 

 are also generally seen in cultivation. 



GEOLOGICAL STRUCTURE. 



The geological range of the county is from the base of the Carbonif- 

 erous system to the Waterlime in the Upper Silurian. The oldest, and 

 hence the lowest, geological horizon is in the north-western portion of 

 the county, occupying Thompson and a part of Scioto townships. The 

 outcropping belts of the formations cross the county from north to south. 

 The townships of Radnor, Marlborough, Troy, Delaware, Concord, Lib- 

 erty, and Scioto are underlain by the Corniferous, including also what 

 there may be of the Hamilton. The belt between the Olentangy and 

 Alum Creek is occupied mainly with the outcroping edge of the Huron 

 shale, including the underlying blue shale seen beneath the Huron at 

 Delaware, in the banks of the Olentangy. How far east of Alum Creek 

 the black slate extends it is impossible to say, but it probably includes 

 the western portions of Kingston, Berkshire, and Genoa. The fragile 

 shales that immediately underlie the Berea grit have a narrow belt of 

 outcrop through Kingston, Berkshire, and Genoa. The Berea grit under- 

 lies the most of Porter, Trenton, and Harlem. The overlying Cuyahoga 

 shales and sandstone, called Logan sandstones in the southern part of the 

 State, have but a feeble representation in Delaware county. They 

 would undoubtedly be encountered by drilling in the extreme eastern 

 portion of the eastern tier of towns. The various strata making the 

 series of Delaware county are as follows, in descending order : 



Cuyahoga shales and sandstones. 



Berea grit. 



Cleveland shale. 



Huron shale. 



Olentangy shale. 



Hamilton and Upper Corniferous limestone. 



Lower Corniferous limestone. 



Oriskany sandstone, or conglomerate. 



Waterlime. 



Cuyahoga Shales and Sandstones. — At Condit, in Trenton township, on 

 the line between sections 1 and 2, may be seen an exposure of the Cuya- 



