96 GEOLOGICAL RECONNOISSANCE 
Most of this ore sent to me, from this mountain, is a white iron pyrites, 
associated with a hydrated oxide of iron, in which yellow iron pyrites is 
diffused. 
Where the Berryville road crosses the Childer’s range of mountains, it 
is elevated about 870 feet above Terrapin creek. The surface rock, at this 
elevation, is sandstone, overlying cherty limestone. 
In the gap of the Osage mountain, the sandstone must be at least 130 
feet in thickness. 
About 11 miles north-west of Carrollton, and three and a half miles from 
W. Jones’s, on the divide between Scott’s prairie and Prairie township, 
magnesian limestones, probably of lower silurian date, crop out, which 
are separated from the limestone and sandstone of the Osage mountain, 
by crisp chert. The upper beds of this lower formation have the same 
earthy character and checkéred appearance on the surface, as the strata 
which form the lower portion of the hills in township 19 north, range 17 
west, and on: Fallen-timber creek, in Marion county, and are, no doubt, 
of the same age. Some of these limestones probably possess hydraulic 
properties. This change in the formations is accompanied by a corre- 
sponding change in the growth, which consists of small oaks, interspersed 
in groves on the hillsides, with a thick undergrowth of sumach and black- 
berries. 
Here, as in Marion county, numerous springs of water issue from 
amongst these earthy, magnesian limestones, and, Howing down the slopes 
render the roads wet and miry. 
The crisp chert, ‘which occurs on this side of Scott’s prairie, has a differ- 
ent lithological appearance from that associated with the subcarboniferous 
rocks on the south-east side of the same prairie, and occupies probably a 
lower geological position. 
The hills about W. Jones’s are composed of the same description of 
magnesian limestones, and crisp chert, with some associate sandstone. 
About midway of the hills, the so-called “ cotton rock” is found: a white, 
close-textured variety of magnesian limestone, which is used for under- 
pinning the houses and building the external walls of chimneys. If placed 
exposed to the direct heat of the fire, it is apt to crack and give way; 
therefore, for the inside lining of fire-places, another bed is preferred 
which lies higher in the hills; this is, however, judging from its external 
appearance, a purer limestone, and, though it may not be so liable to 
crack by heat, it will certainly be more easily burnt to lime. Hereafter 
an analysis of these rocks will be made. 
Several intercalated bands of sandstone occur in the hills in this part of 
Carroll county ; most of them are below the level of the “ cotton rock.” 
