116 GEOLOGY OF ILLINOIS. 



haps as great a distance, it shows itself along the base of the bluffs 

 and hills, often just above the water's edge. Up the smaller streams it 

 can be traced lesser distances. Many of these hills I have found capped 

 with the Blue limestone lying upon the sandstone un conform ably many 

 others exhibit the Buff and Blue lying upon each other conformably; 

 some are capped by the Buff alone; some are nothing but hills of sand- 

 stone, uncapped by even the overlying drift, weathered into shapes re- 

 sembling the pictured icebergs of the Arctic seas. The high bluffs, at 

 the base of which the town of Oregon stands, with the exception of a 

 light limestone cap on the top, are composed of light colored St. Peter's 

 sandstone. At this locality it is about one hundred feet thick. It rap- 

 idly dips for two miles and a half up the river, and finally runs out of 

 sight, the last outcrop observed being half a mile up a little stream, 

 and about twelve feet thick. As we go down the river the thickness 

 increases. About four miles below Oregon, at the fantastic shaped 

 " Indian pulpit," the sandstone peaks rise higher than at Oregon, and 

 before the mouth of Pine creek is reached the elevations measure from 

 one hundred and seventy-five to two hundred feet. After reaching the 

 mouth of Pine creek the formation dips rapidly and soon runs under 

 the overlaying formations. 



Two or three miles above Oregon, on the other side of Bock river, the 

 bluifs rise in a long line along the stream to a hight of perhaps one 

 hundred feet. The debris and talus of these hills present an abrupt, 

 grass-covered slope, to within twenty feet of the top. The rest of the 

 hight is a long, low, beetling mural escarpment of frowning Buff and 

 Blue limestone. The talus covers the St. Peter's sandstone, which 

 doubtless forms the base of the hills. Opposite Oregon, in a low hill, a 

 sandstone quarry and a Buff limestone quarry exist within a few rods 

 of each other. 



Peculiarities noticed while examining this interesting sandstone sug- 

 gest a few observations. 



In many instances hard metallic-looking layers, or bauds, like the red 

 carneliau bands in the trappeaii rocks of Lake Superior in their modes 

 of occurrence, are found running in somewhat parallel planes through 

 the softer material of which this sand rock is composed. These are 

 from one-half an inch to two inches in thickness, and are often within 

 a few inches of each other. As the softer material crumbles away these 

 remain projecting, giving the rocky face of the outcrop a pictured or 

 horizontally veined appearance. The frost breaks these off, and they 

 accumulate in the ravines. They give a hard and ringing sound when 

 struck with the hammer, and almost resemble pieces of old castings in 

 both color and hardness. These layers are ferruginous in texture, and 

 were formed by the oxyd of iron cementing together and hardening 



