320 COUNTY AND EEGIONAL GEOLOGY. 



flood-plain is broad and flat, with, a rich, deep, clayey soil, and 

 being so nearly level it presents a strong contrast with the 

 broken valley-sides which border it. It rests wholly within, 

 and is formed ont of the shaly and clayey members (Nos. 1 

 and 2) of the section at Davis' mill given on a following page, 

 its peculiar characters, and even its existence being due to the 

 soft and yielding nature of those strata. 



Taking the county as a whole, its surface is more uneven 

 than any of those which adjoin it; yet there are quite large 

 tracts of comparatively level land, especially in the south- 

 western and northeastern portions. These, and also the 

 other high and more level parts are principally prairie, 

 but the prairies are gradually lessening by the natural 

 growth of forest trees. The diversity of surface before 

 mentioned, while it may render a small part of the land unfit 

 for the plow, adds an equal, if not greater value to the whole 

 region by giving to the landscape beauties it could not other- 

 wise possess. 



The streams of this county are all tributary to the 

 Missouri river, and as may be seen upon the map, are quite 

 numerous, all having a general southerly course. The whole 

 surface is consequently so well drained that scarcely a pond 

 or marsh of any size exists in the county except occasionally 

 one adjacent to the streams. 



Much good water-power is furnished by Grand river, but 

 the other streams of the county are usually too small for 

 such purposes. 



Geology. The Upper coal-measure formation almost alone 

 is found in Decatur county, the upper layers only of the 

 Middle coal-measures appearing in the valley of Grand 

 river near the southern boundary. If a line be drawn 

 directly north and south through the center of the county, it 

 will be found that all the exposures of rock, in place, appear 

 in the western half, none having thus far been observed in 

 the eastern half. Weldon's creek and Little river, both of 

 which traverse the eastern half of the county from north to 

 south have eroded their valleys to considerable depth below 



