JO DAVIESS COUNTY. 33 



most of the detritus thus formed was removed. The second epoch was 

 one in which the waters or modified drift forces had partially or wholly 

 subsided : chemical and atmospheric agencies worked upon the com- 

 paratively naked rocks ; and the lead basin clays settled down in the 

 places where the underlying rocks had decayed. Such a condition of 

 things would, I think, explain all the phenomena observed in the lead 

 region of this county. How far it might apply to other portions of the 

 north-west lead region, I am unable to state. 



The Xifif/ara Limestone. All the mounds, mound-like ridges and 

 plateaus mentioned in speaking of the topography of the county, are 

 capped by massive irregularly-bedded dolomitic Niagara limestone, 

 ranging in thickness from about fifty to one hundred and seventy-five 

 feet. The castellated appearance of these outliers of this great forma- 

 tion, as they cap these mounds, has already been mentioned. Tapes- 

 tried with lichens and mosses, of a dull brown or red color, with cas- 

 tellated and fantastic forms, these rocks at once attract the attention 

 of the mot careless observer. In addition to the mounds, they cover 

 other portions of the county in the south and south-west ; and their 

 ledges and exposures all round the edges, along the bluffs, and where 

 the streams have cut deep channels into their midst, show the same 

 massive, ragged and picturesque appearance observable on the mounds ; 

 except that they resemble more, long, irregularly shaped reddish-brown 

 mural escarpments or walls, carpeted with soft green mosses and feath- 

 ery ferns. 



The superficial area of the county, covered by these rocks, is about as 

 follows, in a general and approximately correct boundary statement: 



The high bluff range, about Pilot Knob, is capped by this rock. It 

 commences a short distance north of the Knob ; the Knob itself is a 

 high pile of Niagara limestone, resting upon the Cincinnati shales; and 

 the bluffs from thence to Small-pox creek continue to show it along 

 their summits. From this latter stream to the Carroll county line, near 

 the point where it crosses Apple river, the upper part of the bluffs are 

 composed of the same rock, and some grand outcrops of almost beet- 

 ling crags may be seen here. These outcrops extend back from the brow 

 of the bluffs, and are the bed rock over all that high plateau between 

 the Small-pox creek and Apple river, extending in a strip several miles 

 in width to the north-east, to about the township line, between ranges two 

 and three east. Still farther to the north-east, and separated from this 

 large field by some narrow belts of galena rocks, about the head waters of 

 Apple river, is a mound-like plateau or table, about four miles long and 

 t\vo and a half wide, and grouped round it are a number of the mounds 

 heretofore named. As already observed, these are all Niagara limestone 

 structures, built upon the underlying Cincinnati shales. 



