28 GEOLOGY OF ILLINOIS. 



the north- west corner of Rush township ; Paige's Mound, near the 

 south line of Courtland township ; Simmons' Mound, near the north- 

 east corner of the township of Stockton; Bentou's and Rice's Mounds, 

 a little north and west of the latter ; one or two mounds or mound- 

 like elevations east of Elizabeth, whose names I did not ascertain ; 

 an elevated, mound-like plateau of several miles in extent, commencing 

 about two miles north of the village of Elizabeth ; and several other 

 such plateaus in various parts of the county. 



The geological structure of these mounds gives them the appearance 

 of gently sloping hills, for a part of the distance up their sides, crowned 

 by abrupt, fancifully weathered, castellated rocks, of a reddish-brown 

 or whitish-yellow appearance. Some of these views, from a distance, 

 have a great resemblance to old mural walls and baronial towers, and 

 vividly recall to memory the wild architectural structures of the middle 

 ages. Their geology is quite interesting, and will be more fully dwelt 

 upon in a subsequent part of this report. 



These same Niagara rocks outcrop in long mural escarpments along 

 the Mississippi and Apple river bluffs, and along many of the smaller 

 streams in those portions of the county where this geological formation 

 is heavily developed. The ledges and exposures, and some of the ab- 

 rupt outliers of the Galena rocks, also present the same picturesque, 

 wild appearance. Some of them present scenes almost as attractive as 

 any in Jackson county, about the Devil's Backbone and the Mississippi 

 Bake Oven. 



It will thus be seen that the topography and physical features of this 

 county are well marked, and attractive in the extreme. 



8 u rfa c e Geology, 



Alluvium. The small water courses of the county have the usual nar- 

 row alluvial bottoms. In some places these spread out wide enough for 

 small farms. Pleasant Valley, along the north branch of Plum river, 

 extends from Morseville to the Carroll county line, a distance of some 

 ten miles ; it is from a quarter of a mile to almost a mile in width, and 

 contains some of the very best farming lauds in the county. These nar- 

 row alluvial bottoms are composed of a rich, brown, marly soil, made 

 up in great part from the wash and detritus from the hills on either side. 

 In but few places can there be noticed the black silt or mud or washed 

 sand of river alluvium. The valleys are all ancient valleys of erosion, 

 floored or built up by recent detritus from the hills, not transported to 

 great distances, nor greatly mixed, and belonging to very recent Qua- 

 ternary deposits. 



TLe Mississippi river bottom, in the upper part of its course along 

 this county, is very narrow in fact that stream almost washes the 



