224 GEOLOGY OF ILLINOIS. 



ty, above the DesPlaines, has few wells that do not fail in a dry season. On 

 the eastern slope of that ridge, in section 30 of Plainfield township, as I am in- 

 formed by Rev. Dr. Clark, of that town, Deacon Caton bored sixty-one feet 

 through the boulder clay, and got water just after striking the solid rock. I 

 do not know the level of the surface at that point, but judge, from what I know 

 of the levels elsewhere in that region, that this well must have reached as low 

 as the lake level, and perhaps lower. 



In the Eagle shaft, at Braidwood station, the coarse sandstones, which accom- 

 pany the Coal Measure shales, yield a very large amount of pure water, a four- 

 inch stream flowing constantly from the pumps. 



Through the artesian well at Joliet penitentiary, water flows freely from the 

 St. Peters sandstonej which was struck at the depth of four hundred and seven- 

 ty-seven feet. The following data will be the means of calculating, approxi- 

 mately, the depth of this bed in most parts of the county, assuming that the 

 dip of the sandstone is regular : 



Levels of points in Will county, above or below " Datum of six feet below 

 the lowest registered water of Lake Michigan," as furnished by the Illinois 

 River Survey, in charge of G-en. J. H. Wilson, U. S. A.: 



FEET. 



DesPlaines river (low water) at county line above Lockport plus 12.150 



" " " " " Lemont (Cook co.) " 13.795 



" " " " "Lockport 13.540 



" " " " below railroad bridge at Joliet 58.657 



" " " " mouth of Rock run 71.640 



" " " " under Kankakee feeder aqueduct 85.268 



" " " " at junction with Kankakee 87.809 



Bluffs at Lockport, east side, plus 74.09; west side, plus 66.27 

 " " Lemont, " " " 102.00; " " " 137.20 



Kankakee river (low water), east line Grundy co 83.110 



" " " " head of feeder, below State dam 69.588 



" " " " " " above " " 69.580 



" " " " Prairie creek 58.498 



" " " " under road bridge at Wilmington 51.501 



" " " above rapids " <( 39.112 



" " " " east line of Will co.. ..27.698 



