94 ILLINOIS STATE ACADEMY OF SCIENCE 



of Gale along a railway cut. The latter, occurring below 

 the sandstone, is seen along a railway cut about a mile south 

 of Thebes where it has a maximum thickness of more than 

 82 feet. It is mostly a light colored, coarsely crystalline 

 limestone, its layers varying in thickness from a few inches 

 to 4 or more feet. It is often called "Cape Girardeau 

 Marble." 



TOPOGRAPHY 



The main lines of drainage are those of Sandy Creek and 

 other small tributaries of Cache River along the east and 

 southeast. Sexton Creek at the southwest and small branches 

 of Clear Creek at the northwest. So complete is the dissec- 

 tion (Fig. 1) that none of the uplands show flat areas more 

 than 14 rniles across and only the largest stream has a flood 

 plain or terrace of greater width. In striking contrast the 

 Mississippi flood plain is so nearly level that drainage is 

 very imperfect. 



SOILS 



According to the classification adopted by the State Soil 

 Survey the soils of the hill region belong to the upland tim- 

 ber types. The chief material of these soils is a fine wind- 

 blown loess of considerable depth somewhat mingled, par- 

 ticularly upon the steeper slopes, with residual soil formed 

 by the disintegration of rocks in place. This soil is very fine 

 in texture, only moderately fertile, and with slight variations 

 it covers most of the upland area. From its color it has been 

 termed red-brown sandy silt loam. Along the streams, con- 

 stituting the floor of the "Hollows," it passes to a light 

 brown sandy silt loam. These silt loam soils are readily 

 eroded both by surface washing and by gullying. 



The soils of the flood plains of the rivers are mostly 

 rather heavy clay loams varying from gray to drab and 

 black. They have a high water-holding capacity and when 

 properly drained are valuable agricultural lands. 



FOREST TYPES 



In a report on the forests of Illinois, Hall (4) has recog- 

 nized for the southern portion of the state two classes of 

 forest types, those of the upland and those of the bottom- 

 land. This classification may in general be followed while 

 at the same time it must be recognized that the various 



