218 GEOLOGY OF ILLINOIS. 



The " soapstone " No. 2 of the section, outcrops along the river bank, about 

 two miles above Wilmington, and, from its close resemblance to the blue shale 

 above the main coal seam, has misled many persons into the belief that the 

 coal could be found farther east. It was only after repeated examinations that 

 I became satisfied of its true position. 



The " flinty sandstone," No. 3, is probably the representative of the com- 

 pact fragmentary clinking limestone which shows a much greater thickness at 

 its outcrop near Wilmington. This lower division of the group there consists 

 of light blue shaly limestones, with occasional bands of these compact layers, 

 fitted for underpinnings, but rarely furnishing material suitable for superstruc- 

 tures. Its outcrop is very limited, being confined to the bottoms of the 

 Kankakee, between the mouth of Forked creek and the ford near the north 

 line of section 12, township 32 north, range 9 east, and the banks of Forked 

 creek below the " county road" running east from Wilmington. Over all this 

 outcrop, the beds are crowded with the ordinary fossils of the group, such as 

 Rhynchonclla capax, R. Tiemiplicata, Ortliis lynx, 0. subquadrata , Leptsena 

 sericea, Strophomena altcrnata, Orthocerata, Tentaculites, corals, bryozoa and 

 crinoidal fragments, with occasionally fine fragments of trilobites. 



A boring upon the island, at Wilmington, gave the following section : 



FEET. 



Blue shaly limestone 15 



Hard, gritty rock, in thin layers 15 



Dark clay shale, with pockets of petroleum 70 



Petroleum is also found filling cavities in the overlying beds of more com- 

 pact limestone, which outcrop farther up the river, and add probably twenty- 

 five or thirty feet to the foregoing section. These beds also frequently contain 

 cavities lined with very pretty crystals of the " doa; tooth spar" variety of 

 calcite. The limestone itself is composed of comminuted shells and crinoids, 

 and yields few fossils in good condition. 



Mr. Jason Franklin reports the following as the section found in his " oil- 

 well," in the south half of section 23, township 32 north, range 10 east: 



FEET. 



Sandstone 15 



Clay shale, with harder bands 115 



Yellow and white sandstone 5 



Blue sandstone 100 



Blue sandstone, with pyrite 38 



As no beds of sandstone are found elsewhere to correspond with the lower 

 beds of this section, and as the upper fifteen feet are evidently the rotten beds 

 of magnesian limestone which form the base of the Niagara group in this 

 region, I am disposed to believe that the lower beds are also limestone. If this 

 is true, the one hundred and fifteen feet of "clay shale, with harder bands" 



