THE SHELBYVILLE MORAINE. 207 



The black muck penetrated in this well is at the base of the Shelby- 

 ville drift sheet. Mr. Mount reports that several wells in the vicinity of 

 Delavan have encountered a similar bed of muck at this horizon. ' 



Attention was called above to exposures along the Toledo, Peoria and 

 Western Railway east of Peoria, and also on the east bluff of the Illinois 

 opposite that city, where the Shelbyville sheet is underlain by a bed of 

 fossil iferous loess similar in texture and in age to that found on the surface 

 of the Illinoian drift outside the limits of the Shelbyville drift sheet. The 

 loess is 8 to 12 feet in thickness, or about the same as on the uplands outside 

 the Shelbyville sheet. It occurs at a corresponding elevation of about 200 

 feet above the Illinois River. Beneath it there is exposed fully 100 feet of 

 the older drift sheet. The thickness of the Shelbyville drift sheet above 

 this loess varies greatly, being in places but 20 feet, while elsewhere it is 75 

 or 100 feet. The variation is due in part to erosion and in part to original 

 inequalities of thickness. As previously noted, these exposures afford 

 excellent opportunity for contrasting the Shelbyville sheet with the older 

 drift and for studying soils formed on the surface of the older drift. 



In the portion of the Shelbyville moraine west of the Illinois River 

 there are several wells 150 feet or more in depth which penetrate a brae till 

 until the level of the base of this drift sheet is reached. In places its depth 

 is more than 100 feet, and seldom does it fall below 70 feet. A large well 

 was dug by William Dickison on the crest of the moraine 2J miles west of 

 Alta. The well entered blue till at less than 10 feet, which continued to a 

 depth of 117 feet. Here a very bowldery bed 4 feet in thickness was 

 passed through, under which a bed of loess was found, specimens of which 

 were examined by the writer. Beneath the loess there is a hard pebbly 

 clay, apparently Illinoian till, alternating with sand beds. Gravel con- 

 taining water was struck at a depth of 156 feet. A well made by John 

 Holmes, jr., one-half mile west of Alta obtained an abundance of water ' 

 at 125 feet in gravel below till. But a boring made for John Holmes, sr., 

 1 mile east of Alta failed to obtain water, though it reached a depth of 370 

 feet, It apparently did not strike rock, but terminated in a fine sand. A 

 bed of muck with Avood and leaves was found at the remarkable depth of 

 245 to 247 feet. The sand below the muck is perhaps an alluvial deposit 

 of pre-Illinoian age. 



In the vicinity of Dunlap the best supply of water is obtained at 100 

 to 112 feet, in gravel and sand associated with the older drift, In the 



