WILL COUNTY, 219 



will correspond with the two upper divisions of the Cincinnati group, as 

 above given; the one hundred and five feet of " sandstones, "the lower division 

 of this group, and the thirty-eight feet of pyritous rock may represent the 

 compact drab limestone, sometimes pyritous, of the Trenton group, the top 

 layers of which are quarried in Saratoga, four miles northeast of Morris, in 

 Grundy county. The whole section, however, is liable to error, having been 

 made by an inexperienced borer. I give it as the only indication, however 

 imperfect, of the underlying beds in this part of the county, with the excep- 

 tion of Mr. Johnson's boring, before given, which did not reach so great a 

 depth. 



SUMMARY. 



The following is an approximate estimate of the total thickness of rock ex- 

 posed and explored within the county : 



FEET. 



Alluvial and Drift clays and gravels 100 to 150 



Coal Measure sandstones and shales 100 " 125 



Niagara group limestones 200 



Cincinnati group limestones, shales and clays 220 " 260 



Trenton group limestones ? * 38 ? 



Economical Geology. 



Among the mineral resources of Will county, the first place is naturally 

 given to 



Coal. Though the outcrop of the Coal Measures covers but a very small 

 part of the area of this county, yet the amount of coal mined therefrom is very 

 large. 



NOTE. During the summer of 1869, an artesian well was sunk at the Penitentiary, near 

 Joliet, and the following section of the bore has been furnished me, through A. J.-Matthewson, 



Esq., of Lockport: 



FEET. 



1. Rubbish 12 



2. Cherty limestone 16 



3. Soft white granular limestone 60 



4. Coarse rock, resembling Niagara limestone 279 



5. Soft shales and clay 110 



6. Clear sharp sand-rock, full of water 50 



Total 527 



It is impossible to make this agree with known outcrops, or with the facts ascertained by 

 borings in adjacent counties. Nowhere in this region, if anywhere, is there such a bed as 

 No. 6 lying upon the St. Peters sandstone of No. 6. If Nos. 4 and 5 could be made to ex- 

 change places, we might suppose the 279 feet of limestone to represent the lower part of the 

 Cincinnati group and the whole of the Trenton. There is probably error in the reqord. 



