GEOLOGY OF SOUTHWESTERN IOWA. 363 



eminently a prairie county, all the woodland it contains 

 consisting principally of narrow belts bordering the larger 

 streams. A young growth of forest trees begins to encroach 

 upon the prairies from the valley-sides, wherever the annual 

 prairie fires are made to cease, but all the space between the 

 valleys is at present gently undulating or rolling prairie. 



The two principal streams of the county are the East Nish- 

 nabotany and West Nodaway, but the Walnut and Tarkeo 

 drain considerable portions. All these streams have nearly 

 a southerly course through the county, which is thoroughly 

 drained by them and their tributaries. Although the surface 

 has a good degree of diversity, it is not so uneven as to 

 render any considerable portion of it inconvenient for cultiva- 

 tion with the ordinary appliances. 



The soil is of both drift and bluff origin, the Bluff Deposit 

 thinning out upon the drift within this county, but both are 

 very fertile and excellent. The valleys of the two principal 

 streams mentioned, have the same general characters that 

 they have in the other counties to the southward through 

 which they pass, and which have already been described. 

 Their sides are very gently sloping, which gives them the 

 appearance of being shallow, although their depth will really 

 average about a hundred and fifty feet from the general level 

 of the adjacent uplands. 



Geology. The geology of Montgomery county is especially 

 interesting from the fact that besides the Upper coal-measure 

 strata exposed in different portions, there are also important 

 exposures of strata of Cretaceous age in the valley of the 

 Mshnabotany, those at the village of Red Oak being the 

 most southerly exposures of strata of that age yet known in 

 Iowa. All the exposures of those strata in Montgomery 

 county are of sandstone, and from the fact of their being 

 most frequently seen in the valley of the Mshnabotany's, the 

 name Mshnabotany sandstone has been applied to the 

 formation. This formation constitutes the lowest Cretaceous 

 strata yet known in this part of the continent, and in this 

 county it is found resting uncomformably upon the Upper 



