MODE OF FORMA TION OF TILL 5 3 



2. The process in the second stage is merely a continuation 

 of the last. The material has been transported farther, kneaded 

 lono-er and more thoroughly commingled. In addition, a small 

 percentage of foreign drift, mostly well-rounded pebbles of 

 small size, has been worked into the deposit. Still, at the com- 

 pletion of this stage, the fine-grained, dark red clay basis and 

 predominance of angular white chert indicate the close relation 

 between this very incomplete till and the undisturbed residuary 

 material. This is the nature of the ground moraine over practi- 

 cally the entire northern half of the county. But in looking 

 for exposures of it, it is necessary to remember that the upper 

 three feet of the typical or completed till in this district have 

 been highly oxidized during the following interglacial epoch, so 

 that in color they often resemble the deposits of stage No. 2. 

 The latter never were of any other color than dark red and 

 reddish brown.' 



The mode of transportation of this imperfectly formed till 

 appears to have been exclusively subglacial. In a very large 

 proportion of exposures in Stephenson county, there is a con- 

 tinuous section from an undisturbed preglacial residuary 

 clay, through every gradation to what may be considered typi- 

 cal of the " semi-residuary " class of drift. There is absolutely 

 not an iota of evidence that any of this material has been lifted 

 from the earth's surface and enclosed in ice. Clear evidences of 

 a kneading or rolling over of the mass are abundant. 



3. There existed under the glacier, certain areas where depo- 

 sition was being carried on at the same time that abrasion was 

 active in others. So that, while in many portions of the county, 

 the manufacture of till was carried into the second stage only, 

 on certain closely adjoining areas this was but the beginning or 

 early stage of the glacial action. In these latter, the ice after hav- 

 ino- removed the red clay, proceeded to attack the loose sand-like 

 mass of dolomite crystals, which it quickly disposed of by incor- 

 porating with the deposits of stage No. 2, furnishing their first 



' This red til! is best exposed in several cuttings of the I. C. R. R., about three 

 miles southeast of Winslow. in Stephenson county. 



