184 ILLINOIS ACADEMY OF SCIENCE 



The opinion largely prevails that the preglacial surface 

 was a peneplain with old or mature valleys carrying off 

 the surplus waters so that the damming influence of the 

 glacial ice on the eastern margin changed the direction of 

 flow of Apple River while at the same time the mighty 

 waters resulting from the melting ice on all sides, but par- 

 ticularly to the north, combined to change very strikingly 

 the ancient aspect of the surface. We find now a multi- 

 tude of valleys, often with precipitous slopes, and all trend- 

 ing southwesterly towards the Mississippi River, with the 

 exception of the upper course of Apple River, which fol- 

 lows the preglacial axis northwest to southeast. The general 

 outcome of all this battling of the erosive powers of the 

 past is a topography exceedingly broken up into valleys, 

 ravines, hills, ridges, and mounds, rendering a large 

 amount of the surface too rough for cultivation. Fully 

 twenty per cent of the entire county is thus too steep for 

 safe agriculture ; or to express it in sq, miles and acreage, 

 100 sq. miles or 64,000 acres are practically untillable. All 

 of these valleys before mentioned originally had living 

 water courses, and while many of the larger ones yet pos- 

 sess streams of very erratic flow, most of the smaller drain- 

 age lines carry water only in spring or at times of espe- 

 cially heavy rains in winter and summer. This result, as 

 will be shown more fully later, has been brought about by 

 forest destruction; for it is the consensus of opinion 

 among foresters that while forests do not in any way in- 

 crease the amount or volume of water in streams, they 

 play an important part in the fluctuation of those 

 streams. -"^ 



The Soils. 



There is no question that the ancient soil of this region 

 was in the main the disintegrated rock of the three forma- 

 tions that underlie the surface, viz., the Niagara, Maquo- 

 keta shales, and Galena, more or less modified by plant 

 growth (if any such existed in those remote ages), by wind 

 action, and, along the valley drainage channels, by erosion. 

 Such disintegration would have produced clays of various 

 character, and remains of these ancient soils are in fre- 

 quent evidence in many places where extensive weathering 



^ Diminishd Flow of Rock River in Wisconsin and Illinois and its Relation to 

 surrounding Forests, by G, F. Schwarz. Bull. 44, U. S. Forest Service, Wash- 

 ington, D. C, 1913. 



