368 COUNTY AND REGIONAL GEOLOGY. 



have in the other counties before described; namely, a broad 

 gently inclining flood-plain and gently undulating valley- 

 sides, which slope very gradually to the adjacent uplands. 

 The character of the smaller valleys is somewhat similar, 

 but their flood-plains are proportionally smaller, or often 

 almost entirely wanting. The larger streams have eroded 

 their valleys through the Bluff Deposit down to the Drift in a 

 few places, so that the immediate beds have a small propor- 

 tion of gravel and sand, yet the banks are almost invariably 

 muddy, being composed of the fine material of the Bluff 

 Deposit. The character of the great flood-plain of the 

 Missouri river has already been described in the early part 

 of this chapter, and the character of the bluffs that border it 

 have also been described in the chapter on surface deposits. 

 The highest land in the county is almost three hundred feet 

 above the level of the great flood-plain. The eastern two- 

 thirds of the county is principally prairie, but the western 

 third contains much woodland, a large part of it being 

 covered with a thrifty growth of young indigenous forest trees 

 that have sprung up spontaneously as soon as the annual 

 prairie fires ceased by inhabitation of the region, and cultiva- 

 tion of a large part of its soil. The general aspect of the 

 county is one of much beauty, particularly along the valleys 

 of the larger streams; and the ranges of bluffs that border the 

 flood-plain of the Missouri river are often very picturesque. 



Geology. With the exception of two or three exposures of 

 the Mshnabotany sandstone near each other in the north- 

 eastern corner of the county, all the stratified rocks yet 

 observed within its limits belong to the Upper coal-measures. 

 The principal exposures of the Mshnabotany sandstone in 

 this county are on section 23, township 73, range 40, and 

 appear in the east valley-side of the Mshnabotany just 

 below Farm creek. These exposures where opened for 

 quarries, are from ten to fifteen feet in thickness, consisting 

 almost entirely of coarse-grained ferruginous sandstone, 

 somewhat irregularly bedded, with occasional slight inter- 

 calations of clayey material. 



