LASALLE COUNTY. 45 



ing a larger investment of capital to reach it, it has generally been 

 neglected where the upper seams were developed. In McDonough 

 county, where its average thickness scarcely exceeds two feet, it 

 has furnished the main supply of coal for the city of Quincy, in- 

 cluding the river trade at that point for the past twenty-live years, 

 and will no doubt continue to do so for at least another decade. 



The aggregate thickness of the Coal Measures on the east side of 

 the axis, heretofore mentioned, probably does not much exceed 200 

 feet, and the distance between coals No. 2 and 7 is about 80 feet, 

 while on the west side the distance between these coals is about 

 200 feet, and the entire thickness of the Coal Measures may be es- 

 timated at over 600 feet. This variation in the thickness of this 

 formation is probably in part due to the rapid thinning out of the 

 beds towards the eastern border of the coal field, and in part to 

 erosion whicL has carried away on the eastern side nearly all the 

 strata above the horizon of No. 7 coal. 



The details of the following section of the Union Coal company's 

 shaft, at LaSalle, was furnished by Mr. Chas. J. Devlin, the acting 

 Secretary of the company. This shaft is located in the south part 

 of the city, and commences below the main limestones that outcrop 

 along the river bluffs from LaSalle to Peru. 



Ft. In. 



No. 1. Clay shale 11 



No. 2. Brown shale 11 



No. 3. Coal 1 



No. 4. Brownshale 20 



No. 5. Hard limestone 3 



No. 6. Shale 10 



No. 7. Eock 1 



No. 8. Shale 12 



No. 9. Fire-clay 6 



No. 10. Eock 3 



No. 11. Fire-clay 12 



No. 12. Pebblyclay 4 6 



No. 13. Clayshale 10 6 



No. 14. Blackslate 10 



No. 15. Clay shale or fire-clay 15 



No. 16. Coal, No. 7 (?) 4 



No. 17. Fire-clay and clay shale 24 



No. 18. Sandstone '. 2 



No. 19. Black shale 13 



No. 20. Coal, No. 5 ! 5 



No. 21. Clayshale 60 



No. 22. Limestone 5 



No. 23. Shale, with some limestone 1 71 



No. 24. Dove colored shale 12 



No. 25. Coal, No. 2 4 



Total depth 330 



