68 GEOLOGY OF ILLINOIS. 



Leaving the railroad cuts, the streams present the next best opportu- 

 nities to trace the superficial area, thickness, and phenomena of this 

 deposit. The Pecatonica river, about four or five miles after entering 

 the county, strikes the Galena limestone, and for its whole distance in 

 the county, exposes this formation where any rocks are exposed along 

 its banks. There are no very good exposures, however, on this stream, 

 except those at Freeport already referred to. At Bobtown, or New 

 Pennsylvania, an outcrop is worked near the river ; and at or near the 

 mouth of Yellow creek, the formation is dug into in an old crevice lead 

 mine. Eichland creek and Cedar creek both expose the Galena rocks 

 for their entire length. Both these streams have cut deep into the solid 

 rocks, and at many places along their banks heavy outcrops and escarp- 

 ments stand out in bold relief. At Beuna Vista, on the former stream, 

 there is an outcrop of twenty feet, quarried into for its whole depth. 

 At Cedarville, on the latter stream, the outcrop is. seventy-five feet thick. 

 A large quarry is here opened, out of which the stone in Addam's mill- 

 dam have been taken. This is one of the most romantic little places in 

 the county. The high, rocky hills, with their green crowns of evergreen 

 cedars ; the more than Cyclopean walls of solid rock, rising along the 

 banks of the clear, shady stream, and the neat little village, all make it 

 a point not soon to be forgotten. At the Sciota mills, below the conflu- 

 ence of the two streams, and in many places in that neighborhood, the 

 same rocks are exposed and quarried. Crane's creek, where it washes 

 the west end of Crane's Grove, exposes the Galena limestone. It is here 

 quarried for the surrounding prairie to a considerable extent. The same 

 limestone is worked into at Kosenstiel's quarry, near Freeport, to a 

 depth of about twenty-two feet. A hard, gravelly, red clay covers this 

 quarry to the depth of eight feet. Bands of chert also exist in the clay 

 and in the top layers of the stone. 



Leaving now the streams, we will mention some localities examined in 

 other parts of the county. Burr Oak Grove, half way between Lena 

 and Winslow, has near its eastern limits an interesting outcrop. About 

 two and a half miles west of the latter place, almost every little prairie 

 hill top is dug into, and several small quarries opened. An exposure 

 of twenty-four feet was also examined at the lime kiln, a little south- 

 east of Rock City. The top of this quarry is Galena limestone, but it 

 gradually changes into the Blue before the bottom is reached. In the 

 township of Eidott, the Galena is the underlying stone, changing into 

 the Blue towards its eastern and south-eastern part. In the township 

 of Oneco, the formation is heavily developed. In short, the outcrops of 

 this well known formation, or division of the Trenton rocks, are so nu- 

 merous that we do not deem it necessary to particularize them more 



