CLAYS, THEIR ORIGIN, COMPOSITION AND VARIETIES. 



55 



Geological Scale op Ohio. 



IS. Glacial drift to 550 feet. 



17. Upper Barren Coal Measures 



16. Upper Productive Coal Measures. 



15. Lower Barren Coal Measures 



14. Lower Productive Coal Measures. 



18. Conglomerate Group 



12. Sub-carboniferous Limestone, Maxville, Newtonville, etc.. 



Hi? Logan Group, 0-350 / '] 



lldTCuyaho«a Shale, 150-450' 500' 



lie Berea Shale, 20- 50' j- to 



115 Berea Grit, 3 to 160 / 800' 



11a Bedford Shale, 50-150' ■ 



11. Waverly Group. 



f 10c Cleveland Shale. 



10. Ohio Sha'e^ 105 Erie Shale J-250 to 3,000 feet. 



( 10a Huron Shale.... 



9. Hamilton Shale (Olentangy Shale?) 



8. Devonian Limestone, Upper Helderberg or Corniferous, in- 

 cluding West Jefferson sandstone 



7. Lower Helderberg Limestone or Waterlime, including Syl- 



vania sandstone, 50 to 600 feet 



6d Hillsboro sandstone 



6c Guelph or Cedarville limestone, 



50 / -200 / 



Qb Niagara limestone '. 



6a Niagara Shale, including Dayton 



limestone, 5' to 100' 



5. Clinton Group, in outcrop, 20 / to75 / ; under cover, 75 / to 



150' 



4. Medina Shale, in outcrop, 25'; under cover, 50' to 150 / 



3. Hudson River Group, 300' to 750' 



2. Utica Shale, not seen in outcrop, but 300 feet thick under 



cover in Northern Ohio 



1. Trenton limestone, seen only in Pt. Pleasant quarries if at all 



6. Niagara Group. 



500 

 200 

 500 

 250 

 250 



25 



500 



25 



75 



500 ' 



30 ' 



150 ' 



50 ' 



100 ' 



50 ' 



75 ' 



750 ' 



300 « 



50 ' 



U 



PC" 

 CO 



!- 'co 



1. The lowest, or oldest argillaceous stratum that is. known to be 

 worked, or to have been worked for economic use in Ohio is the Medina 

 shale, No. 4, of the table above given. As will be seen from the table, it 

 has a thickness of twenty-five feet in its outcrops, which are wholly con- 

 fined to southwestern Ohio.^_ In fact, it scarcely appears as a surface for- 

 mation at all, even there. Its soft and easily eroded beds account for this 

 fact. It is mainly found in included sections and the number of them is 

 not large. The Medina shale is reddish, whitish* yellowish, or blue in 

 color. The first named color is most characteristic. In composition the 

 shale undoubtedly contains a considerable percentage of lime and mag- 

 nesia, occurring as it does between two great limestone formations, but no 

 analysis is at hand. It has not appeared to be of value enough to justify 

 any outlay in this direction, since but a single application of it to 

 economic uses is known in the state. Twenty years ago, one of the most 

 conspicuous beds of the shale exposed in the state was worked to a mod- 

 erate extent for the manufacture of common drain tile in connection with 

 the ordinary clays of the Drift. The locality is on the National Road in 

 Miami county, as the road descends from the east into the valley of the 

 great Miami River. The clay is said to have proved satisfactory in the 



