18 DRIFT DEPOSITS OF ILLINOIS. 



Total 129 



The bed of cemented gravel at the bottom of this section may 

 be a bed of ferruginous conglomerate belonging to the coal 

 measures, as such a bed is frequently encountered in the upper 

 part of that formation. 



At Odin, four miles east of Sandoval, a similar bed of black 

 soil was encountered near the base of the drift, but no detailed 

 record of the overlying beds was preserved. 



South of the 0. & M. railroad the drift deposits diminish in 

 thickness, and the following section, obtained from a boring for 

 coal at Lementon, in St. Cla'r county, will afford a general 

 idea of their average thickness and diversified character in 

 Southern Illinois: 



Feet. 



Soil : 3 



Ye'low clay .- 14 



Sand and gravel 1 



Blue clay 20 



Blue clay (soil?) 1 



Blue and yellow clays 11 



Bed and yellow sand 7 1 



Total - ; 51 



The foregoing sections afford a fair exhibit of the superficial 

 deposits of this State, all of which may be included in the gen- 

 eral term drift. They cover more tha.n two-thirds of its entire 

 area, including the central and northern portions of the State, 

 where these deposits attain their greatest development. 



In the southern portion of the State, for a distance of fifty to 

 seventy-five miles north of the Ohio river, foreign material is 

 comparatively rare, and often absent altogether, arid when 

 found the boulders are of small size, seldom exceeding a few 

 inches in diameter. 



