172 GEOLOGY OF ILLINOIS. 



of shales, and the small upper (16 inch) vein of coal has been somewhat 

 worked in former times, and in the hill side a little distance to the north of 

 this point, I observed many large boulders or fragments of Coal Measure lime- 

 stone, which may perhaps indicate the presence in the body of the bluff, of 

 the heavy limestone beds which occur above this coal, farther to the south. 



Fischer's coal nv'ne is situated on the railroad nearly two miles north of the 

 village of Petersburg, and nearly at the base of the river bluffs. The follow- 

 ing is the section afforded by the main shaft : 



FEET. IN. 



1. Surface soil and Drift clay 46 



2. Shale 14 



3. Hard, dark colored limestone 4 



4. Black slate 2 



5. Coal No. 4 6 



6. Fire clay and shale 8 



The hard limestone, No. 3 of this section, lies very irregularly upon the 

 dark slate, its average thickness, however, is in this shaft not more than stated 

 above. Discina nitida, and one or two other of the species most common in the 

 roof slate of the coal occur also in this limestone, though less abundantly. A 

 shaft which was sunk by Captain Taylor, near the railroad station, about three- 

 quarters of a mile farther south, passed through the same beds, but as this 

 shaft commences higher up on the hill side, some thirty-five feet of the shale 

 was penetrated, and the limestone and slate were rather better developed. 

 The coal No. 6, would doubtless be met with in a shaft sunk from the top of 

 the hill, and perhaps the small upper vein also. 



On the eastern bank of the Sangamon, in the center of the eastern part of 

 section 1, township 18, range 7, and about half a mile above the railroad 

 bridge, I observed an exposure of a reddish-brown, shaly sandstone, extending 

 about two hundred yards along the river bank, and rising to a hight of seven 

 or eight feet above low water mark. The rock is precisely similar in appear- 

 ance to that in a similar exposure on the river bank above Petersburg, which 

 has been described on a preceding page, and which was then said to overlie the 

 coal No. 6. If it is identical with that, it will show a dip of at least twenty 

 or thirty feet to the northward, between Fischer's and this place, a distance of 

 rather less than a mile. A similar sandstone is said to have been quarried in 

 former times, by the early settlers, in the northwest quarter of section 36, 

 township 19, range 7, on the edge of the river bottom at the base of the bluffs. 

 At present no rock in place is visible, but the scattered fragments, or quarry 

 chips are identical in appearance with the rock in section 1, township 18. 



The boring at Sweet-water, penetrated to the depth of one hundred and 

 seventy-five feet. After one hundred and ten feet of Drift and. surface 

 deposits, the order and thickness of the different beds was reported as follows: 



