10 ECONOMICAL GEOLOGY. 



ally inferior in quality to that obtained from the Troy shaft, in 

 Madison county. A bed of gray limestone, probably the Shoal creek 

 rock, was found in this shaft immediately below the surface deposits, 

 which were here only about 25 feet in thickness. 



At Trenton the shaft is 320 feet in depth to the top of the coal. 

 No detailed record of this shaft was kept. The coal is five feet in 

 thickness, and of excellent quality, and is said to bring from one 

 to one and a half cents per bushel more in the St. Louis market 

 than the Collinsville and Caseyville coals. The roof shales contain 

 Lfiiia tncurntdki, which I regard as a characteristic fossil of coal 

 No. 7. 



At Troy, in Madison county, the shaft is 315 feet in depth to the 

 top of the coal. The seam here is 5^ feet thick, and in quality it 

 is equal to that obtained from the Trenton shaft. The shale over 

 the coal is similar to that at Trenton, and contains the same fossils. 



The Nashville shaft, in Washington county, is about 414 feet in 

 depth to the top of the coal, and the following detailed record was 

 made : 



Ft. In. 



No. 1. Surface clay and gravel 38 



No. 2. Blue shale 4 6 



No. 3. Limestone 6 6 



No. 4. Black slate 4 



No. 5. Coal (aiiddle slaty) 2 



No. 6. Clay shale 6 



No. 7. Sandstone and sandy shale 55 



No. 8. Limestone 4 



No. 9. Blue shale 14 



No. 10. Pebbly limestone 2 



No. 11. Black slate 1 6 



No. 12. Fire-clay 4 



No. 13. Clay shale 8 



No. 14. Sandyshale and sandstone 47 



No. 15. Blue shale (bottom slaty) 26 



No. 16. Coal 1 2 



No. 17. Fire-clay 1 g 



No. 18. Lime conglomerate 4 <> 



No. 19. Sandy shale 63 



No.20. Blue clay shale .,42 6 



No.21. Blackshale 6 



No.22. Fire-clay " l 8 



No.23. Blueshale 3 



No. 24. Fire-clay 4 g 



No. i5. Lime conglomerate 5 



No.26. Fire-clay l 6 



No. 27. Hard limestone 15 10 



No. 28. Blackshale ~ 3 8 



No. 29. Blue pebbly shale 3 



No. 30. Sandy shale and sandstone 14 



No.31. Fire-clay ! 



