140 MISSOURI BOTANICAL GARDEN. 



Quaternary Deposits. 



In their deposition and arrangement the Mississippi, which, 

 unUke most rivers in southern Illinois, follows the pre-glacial 

 drainage lines,* played an important part. 



1. Recent alluvium. — This is of the same nature as that 

 in St. Louis county, however, it overlies a bed of sediment 

 consisting chiefly of an upper sandy portion and a lower part 



;ed of gravel and pebbles. This is well sho 

 made during the summer of 1905 in the 

 Mound, 111., just north of the line dividin 



by 



and Madison counties. Records of the borings^ of which 

 samples were placed in the museum of the Academy of Science 

 of St. Louis through the agency of Mr. J. J. Lichter, were 

 published by Bowmanf and are here reproduced as Table L 

 In this table, which was verified by a comparison with the 

 samples just mentioned, certain of the borings which ap- 

 peared to be identical have been added toerether for the nur- 



condensing 



of glacial origin. Bowman,! 



deposits above referred 



:ht 



believes 



from 

 d and 



How rapidly the river is building out the flood plain may be 

 judged by the fact that Cahokia, one mile cast of the river, 

 in 1850 was situated on the bank of the river. The tribu- 

 tary streams too carry large burdens, as evidenced by the 

 deposits near French Milage, or the instance quoted by Bow- 

 man who mentions the fact that the southern outlet to Pitts- 

 burg Lake has been largely closed up by bluff sediments of 

 Druit Creek. 



2. Loess. — This covers the hills to a greater or less depth, 

 and often reaches a thickness of GO feet, as at the quarry near 



^ — ~ — -j*^ 



* Leverett, F. The Water Rosources of Illinois. U. S. Geol. Surv. 



Ann. Rep. 17^:706. 1895-1890. 



f Bowman, I, Water Resources of the East St. Louis District, HI. 



State Geol. Surv. Bull. 6 : 106-107. 1907. 

 J loc, cii. 





