218 THE CLAYS OF ARKANSAS. 
CaldwelVs pottery. — A small deposit of bluish-white sandy clay- 
mottled with red is found on the north side of a small creek in the 
SE. I SE. \ sec. 10, T. 6 N., R. 31 W. This was at one time used 
to supply a pottery at Greenwood owned by Mr. Caldwell, but clay 
from this place has not been used for a number of years. 
UNION COUNTY. 
GENERAL GEOLOGY. 
The strata underlying Union County consist almost exclusively of 
soft uncompacted clays, sand, brown coals (or lignites), and gravels 
of Tertiary age. The horizontality of these beds makes the geology 
comparatively simple. The clays are of various colors, exhibiting 
all the shades of brown, yellow, red, and gray. The highest beds 
of the county are those that cap the divide on which Eldorado 
stands. These beds are sandy clays and clayey sands, covered here 
and there by gravels of novaculite and quartz. From this elevated 
divide the surface of the county slopes away on all sides, the streams 
cutting deeper and deeper into the soft horizontal rocks. Along 
their banks, where bold headlands are left in the process of stream 
erosion, the stratification of the Tertiary beds is occasionally well 
exhibited. The best exposures, however, are in the river bluffs 
along the Ouachita at places where the river hugs the foot of the 
bluff closely, as at Camden, Newport Landing, Millers Bluff, Wil- 
mington Landing, and New London. At Wilmington Landing the 
section exposed is typical of the geology of the entire highland 
region of the county. 
The beds there exposed continue with some variation toward the 
west and underlie a large part of Union County, and in all proba- 
bility underlie Columbia County also. In the deeper channels of 
the larger streams the beds of soft rocks are penetrated to greater 
depths and the entire section given on page 220 is exposed here and 
there, though generally only in fragments. 
Where erosion has not been so powerful and so concentrated as 
in the immediate neighborhood of Ouachita River the stream chan- 
nels are broader and their sides less -abrupt, so that the clays and 
other beds have thinner coverings along the side valleys that extend 
inland from the river. 
The lignites of Union County are of the same kind as those of 
Ouachita County. Aside from any direct use to which the coal 
may be applied, it serves as a guide in searching for clays, for the 
clays are at many places associated with the lignite, either over- 
lying or underlying it. Persons acquainted with the geology of 
this county report that at many places a bed of clay 15 feet thick 
overlies the lignite. The clay beds at Wilmington Landing and at 
