34 GEOLOGY OF ILLINOIS. 



Brownish-black shales 2 6 



Hard black shale 2 



Gray argillaceous shale 6 6 



The fossiliferous shale in the above section contained Eiiom/phalus 

 sub-rugosiis, Pleurotomaria Grayvillensis, Nucida ventricosa, Lophophyl- 

 Iwm proliferum, Chonetes mesoloba and a leaf of Xeuropteris. 



Section on the Embarras river, S. W. qr. of sec. 31, T. 7, K. 10 : 



Ft. In. 



1. Covered slope •_ 10 



2. Bluish-brown argillaceous shale 10 



3. Brown and black bituminous shale 3 



4. Fire-clay 3 



5. Gray fossiliferous limestone 10 



6. Bine argillaceous shale 4 



7. Brownish-black impure limestone 3 



8. Blue shale 2 



9. Bluish shaly sandstones 10 



The impure limestone, No. 7, contained Productus lonc/ispinus, Athyris 

 subtilita, Pleurotomaria Grayvillensis, Terebratula bovidens, Chonetes mes- 

 oloba and Hemipronites crassus. The shale under the limestone contained 

 Myalina sub-quadrata ? Euomphalus sub-rugosus, Orthoceras Rushensis, 

 fragments of Pinna, etc. Two miles north of St. Marie on the west 

 half of sec. 7, T. 6, R. 11, a shaft was sunk twenty feet to the river 

 level and some fragments of impure limestone were thrown out. About 

 a hundred yards up the river this limestone is just at the water's edge. 

 It is 8 or 10 inches thick and contains Athyris subtilita, Spirifer earner- 

 attis and fragments of Pinna. It is probably the equivalent of the lime- 

 stone near Newton. 



The second blur! or terrace is about forty feet above low water. 

 About thirty feet above low water in the face of the bluff, there are the 

 remains of an old furnace. It is about three feet in diameter, of a 

 circular form and -walled with rock. Around it are pieces of burnt 

 limestone, charcoal and cinders. On the top of the blur! there are a 

 number of Indian mounds arranged in the form of an oblong square 

 inclosing a court. The peculiar arrangement of the mounds, and the 

 presence of mica in the sandstone and also in the drift bowlders found 

 here, led to the belief that silver existed in the rocks and could be 

 extracted from them, and the existence of the mounds and the furnace 

 led to the sinking of the shaft in pursuit of the same precious metal. 



On Crooked creek, a half mile west of Brockville, the following section 

 was. found: 



Ft. In. 



Buff colored lim est one without fossils 4 



Blue argillaceous shale 3 



Rotten limestone with fossils..-. 6 



Black bituminous shale 4 



Blue argillaceous shale 2 



