PUBLIC PARKS OF IOWA 69 



the bottoms is usually 50 or 60 feet, but in the smaller areas the differ- 

 ence is often only 20 or 30 feet. In most of the type the drainage is 

 good, but on the flat areas it is apt to be deficient." 



The usual trees common in the county were observed by the writer 

 sycamore, basswood, slippery elm and American elm, hard maple (Acer 

 nigrum), bur oak, white, chestnut, quercitron, red, black and post oak, 

 red bud, honey locust, coffee bean, black locust (naturalized), hop- 

 horn beam (Ostyra virginiana), white ash, green ash, almond leaved 

 willow, black willow, sand bur willow, cottonwood, river birch, hazel, 

 prickly ash, dogwood (two kinds), hop tree, sumach, poison ivy, fragrant 

 sumach (Rhus canadensis) and wild grape. There are also many interest- 

 ing herbaceous plants, aster, golden rods, violets, lilies, crowfoot, etc. 

 There is a splendid covering of second growth timber, but only a few 

 of the primeval trees are left. It seems to me this land next to the 

 Mississippi river has such a strong tendency to wash that it cannot be 

 well suited for agricultural purposes and sooner or later must be covered 

 with trees to hold the flood waters back. 



The region will make a splendid game preserve and should be ac- 

 quired. Inasmuch as the people of Keosauqua propose to give the state 

 a quarter section, we should acquire the area in question, some 800 to 

 900 acres more so that the area may be rounded out. If we do not ac- 

 quire it this year, I am in favor of acquiring the tract with virgin timber 

 containing some large trees, red, bur and white oak. There are some 

 60 acres in this old timber tract. 



GEOLOGY OF VAN BUREN COUNTY. 

 By Charles H. Gordon, Geologist. 



The present channel of the Des Moines river evidently dates from the 

 glacial epoch. Where the river encounters the limestones of the Miss- 

 issippian or Lower Carbiniferous series, the channel is comparatively 

 narrow with more or less precipitous rock escarpments. 



West of Kilbourne, the soft coal measure rocks descend, passing below 

 the river level below the west line of the county. Here the valley is 

 wider and the slopes more gentle. In the vicinity of Farmington, also, 

 a similar condition prevails, though here in part attributable to depres- 

 sions in the surface of the limestones. This valley therefore well illus- 

 trates the principal "that mature and old forms are more rapidly de- 

 veloped on soft than on hard rocks." As a whole the valley shows the 

 topographical characteristics of youth. 



At the middle of the county, the river forms a loop not unlike an ox-bow 

 in shape. Between the upper points of the loop, the surface is very 

 nearly on a level with the general plain to the northeast, of which plain 

 it forms a part (758 feet above sea level). Along the line of the rail- 

 road this has been reduced slightly by the erosion of the 'branches. It 

 is evident that the Des Moines river flowed over this point, but was de- 

 flected southward somewhat at the very beginning. This course was 

 probably determined by a slight depression below the general plain level, 



