seems to show that as the glacial waters issued from the edge of the 

 ice they were overloaded and struggling with a burden too great for 

 their complete mastery; and, while they successfully carried the silt, 

 sand, and even some of the finer gravel far down their courses, the 

 heavier material in large part lodg-ed near its origin and progressively 

 filled the bottom of the channel. 



"This phenomenon, of which the Wisconsin Valley presents the 

 only complete example lying entirely within the driftless reg'ion, finds 

 other examples in several streams which cross the region. The Black 

 River, the Chippewa, the Mississippi, and the Zumbro are all attended 

 by such glacial flood deposits, which may be traced back to their 

 origin on the face of the outer moraine. All these glacial flood plains 

 slope more rapidly than the present streams. The train in the Chip- 

 pewa Valley falls a little more than six feet per mile in the first 40 

 miles of its course, and over five feet per mile from its source on the 

 face of the moraine to the Mississippi. In crossing the driftless area 

 the glacial flood plain of the Mississippi declines about 50 feet more 

 than the present stream." 



Their description applies as well to the sands of the Havana area, 

 except that the source of the latter is the outwash through the Bloom- 

 ington moraine in the vicinity, as already described by Hart (Hart 

 and Gleason, 1^01 : 139-144). 



The Amboy Area. — This name is given in this report to the ir- 

 regular complex of sand ridges and marshes along the Green river 

 in Lee county, well illustrated in the vicinity of Amboy. Near that 

 place the sand occupies a strip about four miles (6 km.) wide on the 

 south (left) bank of the river. It lies usually in comparatively nar- 

 row ridges from 20-50 feet (6-15 m.) above the intervening marshes. 

 Back from the river the ridges are broader and the marshes propor- 

 tionately more limited in size. Numerous small undrained ponds and 

 swamps lie among the ridges. Near Amboy the ridges are either for- 

 ested or under cultivation, but the number of prairie species occupy- 

 ing the roadsides indicates that at least a portion of the sand was 

 originally covered with prairie. 



Alternating areas of swamp and sand border Green river along 

 its whole course through Lee, Bureau, and Henry counties to its junc- 

 tion with Rock river, a distance of about 70 miles (no km.). They 

 are to be regarded as outwash from the Bloomington morainal sys- 

 tem, which crosses the south part of Lee county from northeast to 

 southwest (Leverett, tSqq: 277, 492, 493). The drainage of the 

 whole valley is poor, and two larg-e marsh areas, known as the Inlet 

 Swamp and the Winnebago Swamp, are as yet not entirely reclaimed. 



