200 THE ILLINOIS GLACIAL LOBE. 



moraine. Several of the valleys have been cut through it to the under- 

 lying older drift, and ravines heading in the newer drift very frequently 

 reach a level below its base before emerging into the older drift district. 

 Wells also not infrequently pass into the older drift before obtaining a 

 supply of water. It is estimated that the thickness of the Shelby ville 

 drift sheet along the course of the moraine in western Indiana averages 

 only 25 or 30 feet aud rarely exceeds 40 feet. On the plain north of the 

 moraine it apparently falls below 20 feet. Before the deposition of this 

 sheet shallow interglacial valleys appear to have been opened and where 

 they were filled the thickness of the Shelbyville drift is in some places 

 perceptibly greater than on the neighboring uplands, so that valleys 40 

 feet or more in depth have in some cases failed to cut down to its bottom. 

 The older drift in western Indiana fills the pregiacial valleys to consider- 

 able depth, often exceeding 100 feet. But on uplands its thickness is much 

 less and apparently averages but little greater than the Shelbyville sheet. 



In the latter part of this report, and in Water-Supply and Irrigation 

 Paper No. 26, on Wells of Southern Indiana, numerous sections will be 

 found which set forth the structure of the drift along the line of this 

 moraine. It is necessary, therefore, to call attention to but a few of the 

 more important sections in this place. These are presented in order from 

 the east westward. 



A well showing a large amount of drift was sunk by L. B. Humphries 

 in the west part of the village of Rockville. For about 40 feet the till was 

 found to be of fresh color and easy to penetrate. This probably marks the 

 depth of the Shelbyville drift sheet, for a hard till was then entered, which 

 continued to a depth of 168 feet. Some wells in the village of Rockville 

 have passed through a black soil at the base of the Shelbyville sheet. In 

 some cases where the ground is slightly lower than at the well just noted, 

 it is found at a depth of but 17 to 20 feet. With the soil there is usually 

 considerable wood. In western Parke County, in the poition of the moraine 

 between Big Raccoon Creek and the Wabash River, wells at several farm 

 houses have passed through a black soil at the base of the Shelbyville drift 

 sheet On a tributary of Big Raccoon Creek, on the farm of E. D. Wicks, 

 in sec. 6, T. 14, R. 8 W., an exposure of soil below till is found at a lower 

 elevation than that struck in the neighboring wells, there being fully 50 feet 

 of till above the soil, while in the wells there is usually but 20 or 25 feet. 



