32 ECONOMICAL GEOLOGY. 



border of one of the ancient valleys which are by no means un- 

 common beneath the drift, and the sandstone, No. 14, formed a 

 projecting ledge, from beneath which the strata had been removed 

 by the denuding agencies of the drift period, and replaced by 

 drift deposits. The drift is here one hundred and sixty feet in 

 thickness, and forms twelve distinct beds between the surface 

 soil and the sandstone. 



The thickness of the coal and the character of the roof, leads 

 to the conclusion that the coal found here is No. 2 of the gen- 

 eral section, which is the lowest workable bed developed on the 

 north-eastern borders of the coal area. 



Mr. T. S. Cummins of Gardner, who has been engaged in pros- 

 pecting for coal in the northeastern portion of the Illinois coal 

 field, has very kindly furnished me with the following short 

 account as the result of his observations in that portion of 

 the coal area: 



"GARDNER, ILL., Jan. 12, 1885. 

 Prof. A. H. Worthen: 



'DEAR SIR: I have read with interest your Economical Geol- 

 ogy of the State, especially that part of it relating to the county 

 in which I reside, and where it has been my privilege to do a 

 great deal of prospecting for coal, and boring for water, from 

 which I have gleaned facts which may be of use to you in de- 

 termining where the seam of coal in the Wilson shaft belongs, 

 which I believe to be identical with that found on the lower 

 Au Sable in Sec. 19. The principal characteristic of this seam 

 is its black shale covering. It overlies the main seam, and is 

 separated from it by sandstone and argillaceous shales aggre- 

 gating 70 to 80 feet in thickness, except near the outcrop 

 to the north and east, where the rocks between get thinner, and 

 the seams of coal come closer together. I have bored through 

 both seams south and west of the Wilson shaft, in South Grove 

 township, Livingston county, on the farms of Messrs. Clover, 

 Eldred and Pratt. The drift in that neighborhood was about 

 100 feet, then four feet of black slate, then the coal about 2 

 feet 6 inches. The other seam is 75 feet lower and 3 feet thick. 

 I have traced it from this point to within a half mile of Brace- 

 ville, where it is found in a well south of the old Augustine 

 shaft at a depth of 48 feet. I also found it on the south line of 



