THE SHELBYVILLE MORAINE. 203 



city of Shelby ville, in the street grading leading from the court-house east- 

 ward to the wagon bridge. Another is found about a half mile east of the 

 wagon bridge, where a road leads off to the south. At this place there is 

 a well-defined soil (Sangamon) between the white clay and the underlying 

 Illinoian drift. The contrast in hardness of the drift sheets is very striking, 

 the drift of the Shelby ville sheet being fresh and easily penetrated by spade 

 or trowel, while the older drift is partially cemented and its brownish-blue 

 till is traversed by veins of deep-brown color not seen in the blue till of the 

 Shelbyville sheet. No better place to study the two drift sheets has been 

 found than is afforded in the vicinity of this city. There are exposed in 

 vertical section numerous cuttings and exposures of both drift sheets, 

 including also the buried soil and the buried white clay which caps the older 

 drift. The topographic features of the two sheets are also well displayed. 

 The contrast is not exceptionally striking here, but the opportunity for 

 making comparisons is exceptionally good. 



In the vicinity of Macon, the first town of importance situated on the 

 moraine north from Shelbyville, an inexhaustible supply of water is found 

 in sand and gravel near the base of the Shelbyville drift sheet at a depth 

 of 100 to 120 feet. The quantit}^ of water is so great as to have prevented 

 the sinking of a coal shaft at this town. Gras in considerable amount has 

 been encountered in wells between Macon and Decatur, and also over a 

 considerable area east of Macon. The gas is found in beds of sand and 

 gravel, which are in some instances located in the lower part of the Shelby- 

 ville drift sheet, but more often in beds associated with the underlying 

 Illinoian drift. In some cases the gas is found in the shale which immedi- 

 ately underlies the drift. Well drillers can readily distinguish the Shelby- 

 ville drift sheet from the underlying Illinoian drift, and they report that it 

 is not uncommon to find a bed of white clajr, such as caps the district 

 outside the Shelbyville sheet, at a corresponding elevation under the 

 Shelbyville sheet. The thickness of the Shelbyville sheet ranges from 

 60 to 120 feet or more, and there is usually so little sand and gravel asso- 

 ciated with it that the tubular wells are sunk into the underlying older 

 drift. 



At Decatur the records of a coal shaft and air shaft 1 show marked con- 

 trasts in the drift sections. The distance between the shafts is about one- 



1 Published in the Geology of Illinois, Vol. VIII, pp. 15 and ( 



