30 Trans. Acad. Sci. of St. Louis. 



of which is a basalt, may be seen sixty centimeters to 

 seventy centimeters in longest diameter. This ravine also 

 affords an east and west section across the south end of 

 Chain of Rocks bluffs. 



Near the south end of the settling basins of the Chain 

 of Rocks water works a road leads diagonally up the 

 bluff. Drift exposures may be seen from the base of the 

 bluff until within twenty feet of the top, the last twenty 

 feet being loess. A deeply cut ravine on the west side 

 of the bluff heads near this section, the divide at this 

 place being about twenty rods wide. The west side of 

 the bluff consists of drift, as determined by sections in 

 the ravine from the head to the lower end. This drift 

 in general resembles that on the east side, except that 

 the larger bowlders are missing. 



The best exposure on the river side of the bluff may be 

 seen where the municipal railway turns away from the 

 Columbia Bottom road (Fig. 6). This section is several 

 hundred yards long and shows glacial material thirty to 

 fifty feet thick, covered by the usual loess deposit. Inci- 

 dentally it may be remarked that this section atfords a 

 fine example of slipping, making the loess appear to lie 

 between two drift deposits. There is marked evidence of 

 stratification, differing from the patches of drift found 

 elsewhere in St. Louis. This stratification appears to be 

 characteristic of the Chain of Rocks material. The sig- 

 nificance will be pointed out later in this paper. The sec- 

 tion just referred to is marked for its abundance of 

 erratics, such as granite, varying from a very close to a 

 very coarse texture, and from a very light to a very dark 

 color, basalt, greenstone, amygdaloids, rhj^olite, quartz- 

 ite, sandstone, ferruginous chert and quartz geodes. A 

 cubic foot, selected at random, from above the middle of 

 the deposit, furnished 102 pebbles and bowlders, varying 

 from one centimeter to thirty centimeters in diameter, as 

 follows: granite 19, basalt 13, greenstone 10, other ig- 

 neous 10, quartzite 17, sandstone 5, quartz 8, chert 20; 



