50 THE ILLINOIS GLACIAL LOBE. 



reached a depth of 164 feet without entering rock; the bottom of the well 

 is estimated to be but 416 feet above tide. The following section of this 

 well is reported by the well driller, L. Williams, of Columbus City: 



Section in well in Iowa River Valley near Columbus Junction. 



Feet. 



Alluvium ^ 



Blue pebbly clay 7 - 



Sand - 



Blue clay - W 



Sand.... 68 



Total 164 



Dr. Overhalt has a well on the bluff back of Columbus Junction at an 

 altitude 130 feet above the well just noted, which reached a depth of 166 

 feet. It penetrates about 35 feet of loess and yellow till, beneath which it 

 is rnainl}- in a blue till to within 6 feet of the bottom, where sand and 

 gravel are struck. It is probable that the blue till in this and the following- 

 two sections is Kansan. A well made for Hon. J. W. Garner at Columbus 

 City penetrated only 13 feet of loess and yellow till, beneath which 157 

 feet of blue till was passed through before a water-bearing sand was found. 

 L. Williams's well, in Columbus City, passed through 20 feet of loess and 

 yellow till and then penetrated 108 feet of blue till before entering water- 

 bearing sand. Within 2 miles west or south of Columbus City rock is 

 found at depths of only 20 to 40 feet, and the drift is largely a yellow till. 



Near Cairo, in Louisa County, Iowa, two wells on the crest of the outer 

 ridge of the Illinoian drift sheet, at an altitude of about 750 feet above tide, 

 reached a depth of 130 feet without encountering rock. They are mainly 

 through till, much of which is probably Kansan. On the outer face of the 

 ridge, near the base, at an elevation of 50 feet below the crest, a well was 

 sunk by R. Cotter which enters rock at about 50 feet. Rock is also exposed 

 in the bluff of Long Creek, north of Cairo, beneath about 60 feet of drift, 

 mainly till. 



Along the outer ridge of the Illinoian drift in northwestern Des Moines 

 Count}* several deep wells have been sunk, some of which penetrate a bed 

 of peat or muck at about the level of the base of the ridge and the siu-face 

 of the Kansan sheet of drift. It is here that the Yarmouth section given 

 above (p. 42) is found. 



In some places along the outer ridge of the Illinoian drift wells have 



