326 GEOLOGY OF ILLINOIS. 



The Drift, which comprises a series of brown and blue clays, locally inter- 

 mingled with sand and gravel, is spread over the entire surface of the uplands 

 to a depth of from twenty to fifty feet, and perhaps in some places a little 

 more. Boulders of the older rocks are not uncommon in it, and frequently lie 

 scattered along the water courses. These are most commonly granite, or be- 

 long to that class of rocks closely related to it. Wells are seldom sunk through 

 this formation, an abundant supply of good water being commonly found before 

 the lower beds are reached. 



All the stratified rocks that are exposed in this county belong to the Coal Mea- 

 sures, and include all the lower portion of the series, from coul No. 7 to coal 

 2, inclusive. Lower than this the rocks are not exposed. 



Coal No. 7, of the Illinois valley section, has been found only at a few places. 

 It has been worked in or near the north line of section 10, township 14, range 7, 

 along East Fork. In section 10, a shaft has been sunk by Mr. S. C. Francis, 

 which affords the following section : 



FEET. IN. 



1. Yellow ciay 2 



2. Red sand 2 



3. Limestone, nodular 2 4 



4. Clay, light colored 6 10 



5. Clay shale 2 



6. Sandstone . 8 



7. Blue clay shale 4 2 



8. Sandstone 1 4 



9. Blue clay shale 8 



10. Dark colored clay shale 5 8 



11. Coal ;'. 2 



12. Blue clay shale 12 



13. Impure limestone f, 8 



14. Clayshale 8 



1 5. Impure limestone 2 



16. Blue clay shale 1 4 



17. Dark colored clay shale 3 1 



18. Coal. 2 7 



19. Clay, penetrated 1 8 



The shaft had not been sunk any farther at the time I visited it in the fall 

 of 1868 neither had the coal, No. 18 of this section, been tested. This coal 

 appears to occupy the position of coal No. 7, and probably belongs to that seam. 

 The coal worked at the Bradford shaft, which is but a short distance from here, 

 in section 21, is thought to lie some thirty or forty feet below, and is probably 

 No. 6. In section 32, township 10, range 7. this coal has been worked a little, 

 by stripping, along Mud run. 



Coal No. 6 is the principal seam worked in the county. It first appears in 

 the bluff of West Fork, in the southeast part of section 3, township 14, range 6. 



