Drushel — Glacial Geology in St. Louis and Vicinity. 33 



it is not possible to remove the bowlder from its bed with- 

 out crumbling. The material, as a whole, is redder than 

 that south of the Chain of Rocks. On account of this 

 advanced state of decomposition and on account of the 

 presence of Sioux quartzite, it is probable that this ma- 

 terial is a remnant of the Kansan or pre-Kansan ice 

 sheet. The Cheltenham region in St. Louis, elevation 

 600 feet, affords material resembling this section. 



Just above this lower drift (Fig, 11 A) is a bed of inter- 

 glacial clay (Fig. IIC), almost a shale, five feet thick. 

 The structure is columnar and jointed, the texture is 

 compact and close, the color is cherry brown. The 

 coarsest particles vary from three-fourths millimeters 

 to two millimeters in longest diameter. Many grains are 

 water rounded and are chiefly quartz; vein quartz, rose 

 quartz, agate, and chert are the predominating varieties. 

 The amount of coarse material in this clay is very small, 

 as shown by the following analysis. Two portions of 

 the clay, A and B, each weighing fifty grams when well 

 dried, were washed through a wire sieve of three-fourths 

 millimeter mesh, with the following results. Portion A 

 contained 142 pieces, weighing 160 milligrams, average 

 weight being 1 9-71 milligrams. Portion B contained 

 212 pieces, weighing 257 milligrams, average weight being 

 1 15-71 milligrams. Three pieces in B measured more 

 than iy2 millimeters and less than 2 millimeters in long- 

 est diameter. In A no grain as large as this was found. 

 It is probable that the above mentioned clay was derived 

 from older glacial drift by streams and deposited in 

 rather quiet water, as shown by the great uniformity of 

 size of the quartz grains. 



Two portions of the loess, A and B, several feet above 

 the contact with the upper drift sheet, each weighing 

 fifty grams, were treated as described above for the clay 

 analysis. Portion A contained thirty-nine pieces, weigh- 

 ing seventy-three milligrams. The particles were chiefly 

 angular, only one well-rounded water-worn grain being 

 found. The longest diameters varied from three-fourths 



