72 GEOLOGY OF ILLINOIS. 



water's edge, and on the Indiana shore, near the mouth of Rush creek, 

 it is overlaid by a heavy bed of shale, including a soft, calcareous 

 stratum, containing numerous fossils. 



At Webb's ferry the equivalent of the Eush creek shale, alternating 

 with shaly sandstone, again makes its appearance, and at Bonpass, a 

 little higher up, we have the following section : 



Ft. In. 



Loess, with characteristic fossils 30 



Drift clay and gravel 20 



Buff sandstone 10 



Shale and covered space 80 



Thin coal 6 



Fire clay 1 6 



Silicious shale and sandstone 6 



Argillaceous shale 25 



123 



The lower shale in the above section is first seen half a mile below 

 the ferry, and contains fossil plants, Splienophyllum, Pecopteris and 

 Neuropteris, but too fragile to be preserved. 



On the western borders of the county, opposite New Harmony in 

 Indiana, there is a large island formed by an arm of the Wabash, called 

 Fox river. This island is low and flat, and subject to overflow. Soon 

 after crossing Fox river we ascend the Ehillipstown ridge, which bears 

 a little east of north, and strikes the Wabash river at Grayville. In 

 this ridge we find the counterpart of the sections at Cut-off, below New 

 Harmony, and at Grayville ; but the creeks do not cut quite so deep 

 into the argillaceous shales here, so as to show the lowest beds. Just 

 before reaching Ehillipstown, on the New Harmony road, a thin coal is 

 seen in the bank of a branch. Below it there is a few inches of fire 

 clay, and then an argillaceous shale, which is seen in the bed of the 

 branch. Above the coal, which is mostly decomposed, there is a calca- 

 reous band containing fossils similar to those found at Grayville. 

 When first quarried this band is firm and hard, but after long exposure 

 it becomes soft. Above the fossil band there is a few feet of argillace- 

 ous shale and a bed of sandstone, as seen in the following section : 



Ft. In. 



Yellow crumhling clay 20 to 40 



Loess with fossils 20 to 30 



Drift, with pehhles and small granite howlders 35 



Silioious shale 10 



Sandstone 2 



Argillaceous shale - 10 



Calcareous fossil band 3 



Fire-clay 1 



Thin coal and fire-clay 5 



133 3 



About a quarter of a mile south-west of this the sandstone of the 

 above section is ten feet thick without seams. It is micaceous and soft 

 when first quarried, but hardens on exposure and makes a good durable 



