extensive areas of each are still in their original condition, or but 

 slightly modified by pasturing. 



Below Savanna, sand deposits of the same age again appear and 

 continue intermittently down the Mississippi into Rock Island county, 

 where they connect with those of the Oquawka area described later. 



The geological origin of these two sand areas is known with con- 

 siderable accuracy. Both are approximately contemporaneous and 

 are derived from outwash from the Wisconsin glaciers. The method 

 of deposition has been well described by Chamberlin and Salisbury 

 {i8S^: 261, 262), with special reference to the Hanover area. 



"The fringing deposits of glacial zvaters. — Outside the moraine 

 lie two classes of deposits which g-athered apace with it. The pre- 

 cipitation which fell upon the western slope of the glacial lobe, to- 

 gether with the water which arose from the same part of the glacier 

 by melting, was shed from the edge, except the portion which may 

 have found exit beneath in other directions and the portion lost by 

 evaporation. Copious streams were doubtless the result. It is not 

 difficult to understand that these, as they issued from the glacier, 

 should have been exceptionally charged with silt, sand, and rolling 

 stone, and that, as turbid waters, they poured down the channel-ways 

 that were open to them. Long trains of glacial wash stretching away 

 from the edge of the ice and leading down the several valleys tes- 

 tify to the reality of such streams. 



"The most notable flood-train originating on the actual border of 

 the driftless region is that which stretches down the valley of the 

 Wisconsin River. The edge of the ice lobe crossed the Wisconsin in 

 the western part of Dane and Sauk counties. In the immediate val- 

 ley of the ri\'er the moraine is largely composed of gravelly constitu- 

 ents, disposed in kame-like hills and ridges, or undulatoiy and pitted 

 plains, showing' the combined action of wash and push on the part 

 of the glacier and its waters. Originating from this gravelly mo- 

 raine, there stretches away a flood-train of gravel and sand, reaching 

 down the valley to the Mississippi, and, there joining similar gravel 

 streams originating hig'her up, it continues down throug'h the drift- 

 less area and beyond, though only remnants now remain. This val- 

 ley drift originates at a height of about 90 feet above the present 

 level of the Wisconsin River, and as it stretches down the valley 

 gradually declines, so that, as it leaves the driftless region, it is barelv 

 50 feet above the Mississippi. Near its origin coarse cobbles, bowl- 

 derets, and even occasional bowlders are not infrequent. Farther 

 down, the material becomes finer, and, in the lower stretches, onlv 

 pebbles and sand are found. The lessening coarseness of the deposit 



