Malott: The ''American Bottoms'' Region 49 



tary of Clifty Creek, where it appears in the form of springs. Because 

 of subterranean drainage the plain is preserved in nearly the condition 

 left by the lake." 



From the above it seems quite evident that both Siebenthal 

 and Ashley thought the water capable of filtering thru the 

 coarse outwash sands and entering the headward-cutting 

 streams below. Such is not the case at present. Bridge 

 Creek and its smaller replicas, as already explained, enter 

 into openings in the massive sandstone bluffs at the south 

 side of the valley. These openings in the sandstone bluffs 

 are very picturesque, and are in themselves remarkable 

 phenomena (see Figs. 5, 6, and 7). It would appear that 

 the water in the former lake of the ''American Bottoms" 

 filtered thru the sand, or else entered the already considerably 

 enlarged joints in the Beech Creek limestone, which was well 

 up the side of the pre-glacial valley, and under pressure found 

 its way along the magnificent system of joints. It would not 

 appear that there was much opportunity for the discharge 

 of water thru the present subterranean passages for a con- 

 siderable time following the withdrawal of the ice from the 

 region. The water at present enters the openings at an 

 elevation of 620 feet, or slightly lower, and emerges as two 

 or three springs in the sandstone wall at the present valley 

 level at the northeast quarter of section 34, at an elevation 

 of 560 feet above sea level, and at a point slightly less than 

 2 miles southwest measured from the Bridge Creek inlet. 

 While this is an easy line of discharge at present, it is diffi- 

 cult to believe that it was a line of discharge immediately 

 following the ice withdrawal. The waters could have filtered 

 thru the sands after having passed thru the limestone pas- 

 sages ; but it is more probable that they filtered thru the sands 

 all along the western barrier, with suflicient volume to pre- 

 vent the overtopping of the sand barrier. Certainly, if the 

 waters traversed the limestone passages at all immediately 

 following the ice withdrawal, they went thru very slowly, as 

 these passages must have undergone most of their enlarge- 

 ment subsequent to the ice period. Moreover, the valley into 

 which the present outlets debouched was a filled valley, and 

 has only in recent times been excavated to the level where 

 the present springs emerge. 



i*F. Leverett, The Illinois Glacial Lobe. Monograph XXXVIII, United States Geo- 

 logical Survey, 1898-99. P. 103. 



