756 



T. C. CHAMBERLIN 



for the valley is not occupied by a permanent stream. The slope 

 on the southward side is about as steep on the average as can be 

 profitably cultivated; that on the north side is steeper, so that 

 while the upper slope is cultivated the lower slope is left to nat- 

 ural growth and is partially occupied by quarries. On this steeper 

 portion there are some small, vague, bench-like lines of uncertain 

 interpretation; quite likely they are structural features depend- 

 ent on the alternation of the more and the less resistant layers of 

 the underlying strata. About twenty-five feet from the base of 

 the slope there is an ill-defined bench that seems to be made up 



Fig. 5. — Section through the mouth of the tributary valley and the ridges on the 

 north and south. Merely diagrammatic. 



of lodgment matter adjusted to a former higher axis of the val- 

 ley. There is a correspondingly vague bench on the opposite side. 

 The ridges are composed of Carboniferous limestone, mantled by 

 Pleistocene deposits (Fig. 5). The glacial drift is represented by 

 some bowlders and smaller rubbish, but it is so scant and patchy 

 as to be negligible as an element of the topography. The upland 

 surface is mantled with loess and loam, the main portion of which 

 is probably referable to the Iowan stage. The lower slopes are 

 covered by wash from the uplands and by the skeleton-enclosing 

 deposit which lies near the axis of the tributary valley and con- 

 stitutes the vague benches above mentioned. 



The back country is strongly rolling, the valleys fairly sharp, 

 and their debouchures into the Missouri bottoms abrupt but 

 well adjusted, and in their adjustments they represent the sev- 

 eral normal types as well as several different stages. The 

 bottoms of the Missouri are sharply defined by bluff faces. This 

 is particularly so where the little valley in question joins it. 

 The Missouri here runs southeastward, and the ridges bounding 



