260 
narrowest place in the formation. It is two miles wide. Here the sand- 
stone is 90 feet in thickness and the muddy shale over 200 feet. Both 
the sandstone and shale have been worn away as fast as the limestone 
has receded. For this reason the hills are steep and the country to the 
east is low and flat. 
This is not quite a typical section for this region, because limestone is 
seldom found on the hill farthest to the east. It is usually found a mile or 
more west of the eastern face of the knobs. 
The next section to the north, the Underwood section, was run along 
the middle line of township 2 north. It begins on the west side of the 
Illinois grant and runs west 13%, miles. On the east are found low hills 
called the Guinea knobs, none of which are over 150 feet above the sur- 
rounding country, and most are much lower. On the tops of some glacial 
gravel is found, on others clay, due to the decomposition of muddy shale. 
Fifty feet above the Goniatite limestone there is a layer of muddy shale 
containing iron nodules, and higher up there are layers of blue shale, 
much bluer than is the usual color. 
For four and a half miles west of the Guinea knobs the country is 
generally level; then the outliers of the western knobs are reached. They 
are made up entirely of shale and clay, except the last hill to the west, 
which contains sandstone at the top. The country continues rough for 
three miles and only one valley of any consequence is crossed; it is the 
valley of the Big Ox Fork. The last ascent is 250 feet where sandstone 
190 feet in thickness is found. Typical of this formation, the sandstone at 
some depths is much muddier than at others; and in this hill, at the top, 
the sandstone is much muddier than about 100 feet down, where for a few 
feet it is comparatively pure, then it gradually grows muddier until it 
grades into a sandy shale, and still farther down into a nearly pure shale. 
For the next two miles the country is nearly level; it then becomes 
more broken until the limestone is reached, four and one-half miles west 
of the first sandstone hill. Just beneath the limestone there is a layer of 
blue shale; below this is the sandstone. 
The next section, the Scottsburgh section, was run along the middle 
line of township 3 north. It begins in the vicinity of Scottsburgh and con- 
tinues westward 131% miles. It is comparatively level for 10 miles, the 
country being covered with alluvium and glacial and residual clays. The 
first hill of any consequence is capped with muddy sandstone, the second 
by the Subcarboniferous limestone. 
