WILL COUNTY. 217 



mentioned, and are probably equivalent to the middle of the Rock run 

 section.' 



At the mouth of Rock run, near the east line of section 35, township 35 

 north, range 9 east, considerable stone has been quarried for local use. It is 

 a thin-bedded, very argillaceous limestone, originally blue, but weathering first 

 rusty and then light-drab, with bands of chert near the top of the quarry, and 

 more or less pyrite scattered through the whole mass. Fossils are abundant, 

 but rather fragmentary, including Orthocerata, various brachiopods, a few 

 trilobites, and some fucoidal markings. The thickness exposed is nearly forty 

 feet. 



Near the bridge over the DesPlaines, in the northeast quarter of section 21, 

 township 34 north, range 9 east, we find these beds of limestone thinned out 

 to about ten feet, between the Niagara limestone and the underlying green 

 shale. They here contain an abundance of Petraia and Orthis, with an occa- 

 sional Cafymene, and one or two other forms. No equivalent of these beds 

 has been recognized upon the Kankakee, though it may possibly be repre- 

 sented among thelmff limestones of this group, near the southeast corner of 

 the county. 



The bed of green shaly clay which forms the middle division of this group 

 in this county, is a perfectly homogeneous, fine-grained clay, with no fossils, 

 and no impurities of any kind so far as observed. Along the DesPlaines, 

 through the east half of township 34 north, range 9 east, this bed is known 

 to be from forty-five to fifty feet in thickness, and it is not less than 

 that on the Kankakee, where it is first observed just above the mouth of 

 Prairie creek, on the north bank, and thence accompanies the outcrop of the 

 overlying Niagara rocks up the river to near the county line, where it dips 

 below the water level. Above Wilmington, it becomes more impure, and 

 somewhat thinner. 



Below this bed, along the Kankakee, especially near and on the banks of 

 Horse creek, there is a considerable outcrop of about fifty feet of drab and 

 greenish shaly sandstones, rather irregularly bedded, and showing fucoidal 

 markings. The same beds, of a locally different character, are exposed for a 

 short distance along the south bank of the Kankakee, opposite the mouth of 

 Prairie creek. From near the top of this bed, a boring has been made at Mr. 

 Johnson's place, on section 13, township 32 north, range 10 east, of which the 

 following is the reported section : 



FEET. IN. 



1. Shaly sandstone 50 



2. Soft clay shale, (" soapstone ") 30 



3. Flinty sandstone 5 6 



4. Blue " soapstone " 24 6 



5. Hard drab clay shale 6 



28 



