148 GEOLOGY OF ILLINOIS. 



Something- like a walled well was, 110 doubt, actually discovered ; but 

 from all the light I could obtain on the subject, I think it was only a 

 rounded excavation in the underlying sandstone a pot-hole, perhaps- 

 worn out by an eddy and moving pebbles revolving in a circular mo- 

 tion. In sandstone, with broken and thin-bedded strata, the inside of 

 such an excavation would present exactly the appearance of an arti- 

 ficial well. And thus, this supposed wonder, like the walled lakes of 

 Iowa, and other supposed works of art, is susceptible of a simple and 

 satisfactory explanation. 



To me the chief interest in the well consisted in the fact, that its walls 

 were built of my newly discovered sandstone, enabling me to trace the 

 general course of its deposit. 



The next outcrop is in the grove about one mile east of Unionville. 

 Here it is quarried to a considerable extent. 



But the most characteristic outcrop is at Unionville, one mile north 

 of Morrison. Here a heavy quarry is largely worked. A section of 

 this quarry shows about nine feet of light marly clay, resembling loess, 

 about three feet of alternating clays and soapstone, and twelve feet of 

 massive, heavy-bedded sandstone. Three strata or layers of the latter 

 outcrop, each from two to three feet thick, separated by layers of soap- 

 stone imbedded in thin seams of clay. One of these soapstone layers 

 is six inches thick. It is of a blue-white color, greasy and unctuous to 

 the touch and feel. The sandstone layers are soft, light-colored, 

 finely grained arenaceous rocks. They can be hewn into any shape 

 with an old ax, but when seasoned and dried, they harden into a fair 

 building stone. The surface of some of the larger blocks is beautifully 

 covered with very distinct ripple and wave marks. 



About seven miles south-east of Unionville, on the Poor farm, is an- 

 other outcrop. It is in the face of the east bluff of the Cat-tail. This 

 quarried outcrop is similar to the one just mentioned. The bluffs on 

 both sides of the Cat-tail, in this vicinity, show signs of this sandstone. 



At Mineral Springs, on Kingsley's Grove, still further to the south 

 west, the borings of a small artesian well showed it to be the under- 

 laying rock. This well was put clown in oil-fever times. Some indica- 

 tions of oil exist about these chalybeate springs ; but after prospecting 

 awhile, the enterprise was abandoned. 



Following the same general course, we next find outcropping sand- 

 stones in the Mississippi bluffs, near Hampton, in Eock Island county. 

 The rock has a resemblance to the Unionville sandstones, but probably 

 belongs to the true Coal Measures, a little higher in the geological scale. 



The sandstone deposit rests unconformably upon the Niagara lime- 

 stone. At one time it w r as thicker, and covered a larger extent of the 

 county, but the erosive and denuding forces of past geological ages 



