108 THE ILLINOIS GLACIAL LOBE. 



at the base of the drift, together with the underlying subsoil, appears to be 

 connected but remotely at least with glacial agencies. The deposit appar- 

 ently antedated the deposition of the overlying till by a considerable 

 interval. The writer is inclined to refer to the Illinoian invasion the series 

 of clavs setting in at 27 feet and extending to 106 feet. 



Worthen reports a section at Virginia, Illinois, in which a black soil 

 appears between tills at a depth of G7 to 70 feet. 1 On making inquiry of 

 Dr. J. F. Snyder, of Virginia, concerning this section, it is found that the 

 record of the coal .shaft on which Worthen based his section of the drift 

 was not kept with a sufficient degree of accuracy to insure its correctness. 

 Dr. Snyder is of opinion that the distance to rock is about 70 feet greater 

 than shown by this record. It would certainly be hazardous to base an 

 important time interval on the reported occurrence of soil in the shaft at 

 Virginia. 



The section of a coal shaft at Bloomington reported by Dr. H. M. 

 Banister 2 represents the occurrence of two buried soils. The section as 

 reported by Dr. Banister is as follows : 



Section of coal shaft at Bloomington, Illinois. 



Feet. 



Surface soil and brown clay 10 



Blue clay 40 



Gravelly hard pau 60 



Black mold with pieces of wood 13 



Hardpan and clay 89 



Black mold, etc 6 



Blue clay 34 



Quicksand, buff aud drab iu color, and containing fossil shells 2 



Total drift 254 



In this section the upper 110 feet may be referred with considerable 

 confidence to the Wisconsin drift. The upper "black mold" at 110 to 

 123 feet was apparently post-Illinoian. It is probable that the Illinoian 

 sheet is represented in the "hardpan and clay" at 123 to 212 feet. The 

 remainder of the section would be therefore pre-Illinoian. Whether the 

 blue clay below the lower "black mold" is a glacial deposit is not clearly 

 shown. It may prove to be a water deposit. In view of this uncertainty 

 it seems unsafe to use this section as evidence for the occurrence of a pre- 

 Illinoian drift sheet in central Illinois. 



1 Op. cit., Vol. VIII, p. 16. - Op. cit., Vol. IV, 1870, p. 178. Also Vol. VIII, p. 14. 



