CLAYS, THEIR ORIGIN, COMPOSITION AND VARIETIES. 55 



Geological Scale of Ohio. 



18. 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 



13. Conglomerate Group 



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

 11* Logan Group,,... 0-350 / ] 



11. Waverly Group. 



-HaTCuyahoRa Shale, 150-450' 



lie Berea Shale 20- 50' 



116 Berea. Grit, 3 to 16C 



-11a Bedford Shale, 50-150' J 



to \ 



soc) 



S6. Niagara Group. 



in 





S3 1 

 g| 

 •"'i/j 



f 10c Cleveland Shale... ) 



-10. Ohio Sha'e^ 106 Erie Shale V250 to 3,000 feet 



(. 1 0a Huron Shale J 



-9. Hamilton Shale (Olentangy Shale?) 



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

 cluding West Jefferson sandstone 75 " 



7. Lower JHelderberg Limestone or Waterlime, including Syl- 



vania sandstone, 50 to 600 feet 500 " 



' 6d Hillsboro sandstone 30 " 



6c Guelph or Cedarville limestone, 



50'-200' 150 " 



6b Niagara limestone 50 " 



-6» Niagara Shale, including Dayton 



limestone, 5' to 100 7 100 " 



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



150' 50 " 



—4. Medina Shale, in outcrop, 25'; under cover, 50' to lb(/ 75 " 



3. Hudson River Group, 300 y to 750 7 . 750 " 



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



cover in Northern Ohio 3Q0 " 



1. Trenton limestone, seen only in Pt. Pleasant quarries if at all 50 " 



1. The lowest, or oHest 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 



