26 



dunes rise much higher. One of the highest Hes about four miles (6 

 km.) north of Topeka, and is probably about 60 feet (18 m.) above 

 the general level. Part of the sand was originally covered with 

 prairie, but most of this has been destroyed by cultivation and pastur- 

 ing, so that only a few small areas remain in their natural condition. 

 A larger portion has been forested, and much of it remains in its 

 virgin state. Particularly large tracts of forest are situated near For- 

 est City and between Kilbourne and Bath. 



^ The Hanover Area. — This region of sand deposition takes its 

 name from the station of the Chicago, Burlington and Ouincy rail- 

 way in Jo Daviess county, which lies near the location of the best 

 development of sand vegetation. As in the Havana area the sand 

 occupies the so-called second bottom, between the bluffs on the east 

 and the Mississippi river on the west. In some places the sand ex- 

 tends to the river's edge, in others a strip of alluvial forested flood- 

 plain intervenes. In the northern portion of the county the bluff's lie 

 close to the river and the sand is limited to small isolated areas. In 

 the southern half the bluffs and river become one to three miles 

 (2-5 km.) apart, affording space for an extensive sand deposit. 

 North of Savanna, in Carroll county, the river again flows directly 

 at the base of the bluffs. The area in Jo Daviess county covered by 

 sand is estimated at 5700 acres (22 sq. km.). 



Unlike the Havana area, the sand deposits here are nearly contin- 

 uous and unbroken by intervening areas of a dift'erent soil. The 

 surface of the area is gently rolling, with virtually no extensive level 

 tracts. Its general elevation is about 25 feet (8 m.) above the river, 

 but isolated dunes reach a much greater height. Near the eastern 

 margin of the valley the depth of sand abruptly decreases, leaving a 

 trough-like valley extending for a long distance at the base of the 

 bluffs. The Chicago, Burling'ton and Ouincy railway lies mainly in 

 this depression. The drainage from the hills enters the valley through 

 a number of small spring-fed streams. None of these has sufiicient 

 energy to erode a valley through the sand, and their discharge merely 

 accumulates in a series of swamps, which are drained by percolation 

 through the sand into the river beyond. The swamps are not con- 

 tinuous, but are separated by tracts of moist ground, originally prairie 

 (the lower prairie of Pepoon, i^0(): 526) but now almost entirely 

 under cultivation. 



The sand deposit is chiefly prairie, but a belt of forest lies along 

 the river, and tongues and irregular areas of forest project out into 

 the prairie, in some places extending nearly across. Some of the 

 forest and most of the prairie have been placed under cultivation, but 



