aoe GEOLOGICAL RECONNOISSANCE 
an extension of one and the same bed. Experience has shown that local 
changes in the composition of the same vein of coal are not unusual, and 
cannot alone be relied upon as a means of identification. The organic 
remains of the roof shales and observations on the superposition of the 
strata, are much surer guides in the determination of the position of beds 
of coal. 
For further remarks on the coals of Johnson county, see the Report of 
Dr. D. D. Owen, State Geologist. 
East of Clarksville, and north of the Arkansas river bottoms, the heavy 
mass of dark shales, associated with the coal, disappear beneath the sur- 
face, and the overlying sandstone becomes the surface rock, with some 
intercalations of shale towards the base. The siliceous soil, derived 
from this sandstone, supports a growth of large yellow pines, on the high 
ridges between Clarksville and Dwight mission. 
Agriculture. 
The tillable up-lands of this county are derived principally from the 
shales lying below the main mass of millstone grit rocks. Sample of 
soils were collected for chemical examination, from Mr. Arthur Davis’ 
farm, one and a half miles east of Clarksville, where the growth was 
‘principally postoak. 
The bottom lands, bordering on the Arkansas river, are highly esteemed 
and very productive. 
POPE COUNTY. 
The geology of Pope county is almost a counterpart of that of Johnson. 
The northern part is broken and mountainous. The mountains are com- 
posed of massive sandstones, belonging tothe millstone grit formation at 
the summit, and thin-bedded and shaly sandstones at the base. Near the 
head waters of Illinois bayou, the upper bed of sandstone is a true con- 
glomerate charged with pebbles, huge blocks of which have rolled from 
above into the valley beneath. 
On Indian creek, the subcarboniferous limestone appears beneath these 
rocks, interstratified with reddish shales. This is the only limestone 
observed in the county. 
South of Dover, between Illinois bayou and Galley creek, and south of 
the Carrion Crow mountains, the country is comparatively level, where 
the siliceous, red and dark argillaceous shales, having no capping of hard 
