130 GEOLOGY OF ILLINOIS. 



just above the Dixon mills. The rock has been quarried here, making 

 room for buildings and to obtain building material, until it presents a 

 perpendicular wall of stone, perhaps forty feet high. The top of this 

 outcrop is real Galena limestone; the middle has somewhat changed in 

 character ; the bottom presents real beds of transition into the under- 

 laying blue beds of the Trenton proper. 



At Demeut's quarry, one mile below this place, and on the north side 

 of the river, and also in a hill at the north end of the Illinois Central 

 railroad iron bridge, bold outcrops of massive, heavy-bedded, cream 

 colored and yellow Galena limestone are largely worked. Thence down 

 the river on the north side for about six miles, to Lawrence's quarry, 

 almost every hill shows a Galena outcrop. Dement's quarry, and a bold 

 stone bluff, projecting over the edge of the river current, about three 

 miles below Dixon, each expose a thickness of nearly seventy-five feet 

 of solid stone escarpment. In this distance there is one heavy exposure 

 in the south bank of the river. At Lawrence's quarry the rock presents 

 a sort of a metamorphic appearance ; and some of the layers are covered 

 with a white incrustation of carbonate of lime, resembling the frosting 

 on a cake. From this last outcrop the banks of the river run low, and 

 show no more rocks until the west line of the county is passed. 



South of Kock river, along these Galena outcrops, the country spreads 

 away in a dead level towards the Winuebago swamps. No rocky out- 

 crops are seen, between this section of the river and the south line of 

 the county ; but this long parallellogram is probably underlaid by deep- 

 laying Galena limestone, and patches of Cincinnati shales, which are 

 shingled over it along the west line of the county. 



North of Kock river the country rolls away in undulating prairie and 

 sparsely wooded stretches, and is all, with the exception, perhaps, of a 

 small corner below the mouth of Pine creek, underlaid by the Galena 

 limestone. The physical features of the country show this at a glance. 

 The Illinois Central railroad, in winding out of the low Eock river 

 bluffs towards Woosuug, makes several long but not deep cuts in the 

 Galena limestone. Several wells in the township of Palmyra disclose 

 it at their bottoms. Along the banks of a little prairie stream north- 

 west of Sugar Grove, at a locality called the Big Springs, two or three 

 excellent quarries are opened and extensively worked to supply the 

 surrounding farms with building stone. 



The outcrops of this formation south of Rock river are not numerous, 

 but still a considerable area is underlaid by it. Commencing at Mount 

 Carroll, in Carroll county, a low anti-clinal axis of the Galena limestone 

 may be traced southeast through Milledgeville and Wilson's Mill to 

 Eock^ river, just west of Dixon ; thence on the same general course to 

 Lee Center; thence bending south and west towards and near Sublette, 



