427 
places and in other places was entirely washed away. Generally, either 
sand or gravel overlies it, indicating that rapid flowing waters followed 
the long period of quiet waters in which the clay was deposited. 
The next step in the history of the Flatwoods region comes with the 
deposition of the loess material. This fine, close-textured, ash-gray-to- 
white material composes the present surface of the region, except where the 
long duration of swamps has built up a black soil, which in some places 
‘is several feet deep over the top of the loess. The loess is somewhat 
uncertain as to its exact time and manner of deposition, and also as to 
the origin of the material. It was in all probability deposited not so very 
long after the disappearance of the IlJniois glacier. Its thickness varies 
greatly in the Flatwoods region. Usually it is very thick at the margin of 
the old lake, being as much as twenty or even thirty feet; but in the cen- 
tre of the region it is much thinner, at times being scarcely discernible. 
It is thicker at the margin because it has been washed from the hills 
adjacent. In the interior, perhaps much of it has been incorporated with 
organic material in the making of the black soils. 
In connection with the history of Flatwoods, McCormicks Creek adds 
a very fascinating chapter. After the withdrawal of the ice, the lowest 
outlet was still the Raccoon Creek col. The region in the vicinity of the 
headwaters of Alliston’s Branch was thirty feet or more higher than the 
Raccoon Creek col, having been built up by a possible moraine and the 
outwash plain already described. Therefore, the waters lowered to the 
level of the Raccoon Creek col. The water within the region was the site 
of a shallow lake, not being any deeper than the lowest place below the 
Raccoon Creek col. But the waters soon fell below the level of this open- 
ing, because of the opening of the old sinks near the margin of the region. 
These sinks were not covered deeply by the silt and sand, and conse- 
quently soon opened their old channels which had been filled or partly 
filled. It is very likely that the sinks formed in the northwestern margin 
or portion of the region in section 23, T. 10 N., R. 3 W., were the lowest 
and were, perhaps, the first to be opened on account of the static head at 
this place. These sinks had been draining this immediate portion of the 
Flatwoods basin long before the advent of the Illinois glacier, and it is 
quite likely that a thorough drainage, though underground, was already 
established along the line of the present McCormick's Creek Gorge. It can 
be easily seen that below the lower part of the gorge the valley hcomes 
wider. and on approaching the river it is a filled valley. This clearly shows 
