78 IOWA ACADEMY OF SCIENCES. 



feet, beneath which a blue gummy clay was found. The drift 

 at Virginia City has a depth of 187 feet, as shown by the coal 

 shaft. This shaft passed through a lower black soil between 

 till sheets at sixty-seven to seventy feet. 



In the south part of the Sangamon basin, in the vicinity of 

 Taylorvillc, 111., the loess, which has a thickness of ten to fif- 

 teen feet, is underlaid by beds of sand and gravel carrying 

 thin peat beds in their midst as well as at the junction of the 

 loess and the sand. At the Taylorville coal shaft the upper- 

 most peat-bed was found at thirteen to fifteen feet, and the 

 lowest at forty to forty- four feet. Numerous exposures of this 

 peaty material, alternating with sand beds, may be seen in 

 ravines in that vicinity. 



In October, 1896, Professor Chamberlin and the writer exam- 

 ined together numerous exposures of the Sangamon soil in the 

 portion of eastern Illinois south of the limits of the Wisconsin 

 drift, chiefly in Cumberland, Coles and Shelby counties. 

 North of Greenup there are exposures where the subsoil 

 beneath the Sangamon soil is traversed by branching root-like 

 tubes one-half inch in diameter, which were easily traced ten 

 to twelve inches below the soil proper. These tubes are filled 

 with the black soil which apparently settled into them upon 

 the decay of tree roots. There seems to us little question that 

 the Sangamon soil here supported a forest. The till below 

 this soil in these counties shows leaching to a depth of several 

 feet. It also presents weathered cracks and seams extending 

 down a depth of twenty feet or more. Similar leaching and 

 weathering below the Sangamon soil has been observed by the 

 writer in several other counties in southeastern Illinois, and in 

 Vigo, Clay and Sullivan counties in southwestern Indiana, thus 

 extending it to the southeast border of the Illinois lobe. 



Returning to western Illinois excellent exposures of black 

 soil and leached subsoil are found along the Santa Fe railway 

 in eastern Knox county, of which views are here presented 

 (see Plate iv). The soil shown in these views may be seen 

 distinctly at a distance of nearly one-fourth mile. It is of a 

 deep black color, resembling the surface muck found in flat 

 portions of the uplands. The till beneath it has been leached 

 to a depth of about four feet. The loess has a thickness of 

 twelve feet and is slightly calcareous in the lower portion. 

 The entire leaching of the till may confidently be referred to 

 a date earlier than the loess deposition. 



