PRAIRIE COUNTY. 161 
The strata west of White River are of late Quaternary age. The 
surface material of the prairie land is a reddish clay loam or gray 
buckshot clay. On the higher ridges, where water does not stand 
for any great period, the surface clay and subsoil is a red clay very 
similar to the second-bottom or terrace clays ajong the west side of 
Crowleys Ridge in Lee and Phillips counties. In the low slash lands, 
which are covered with water for several months during the year, the 
surface clay was doubtless originally the same kind of material as 
that on the prairie lands. But the iron oxide of the prairie soils has 
been segregated into small limonitic concretions, which have received 
the local name of buckshot. The soils of the slash lands are there- 
fore more or less leached and have a white to grayish color. 
The character of the strata found in wells and in the bluff at Devall 
Bluff is shown in the following sections : 
Section of bluff at Devall Bluff. 
Feet. 
Yellow clay loam, in places buckshoty * 10 
Stratified reddish sand, very fine grained 8 
Red plastic clay to bottom of gully 3 
The yellow surface clay is used here for making brick. In the 
prairie land at Tollville, 6 miles southwest of Devall Bluff, the follow- 
ing well record was obtained : 
Record of well at Tollville. 
Feet. 
Yellow clay 3 
Hardpan, gray clay 10 
Reddish clay grading into a gray sand 20 
Very fine quicksand, supplying water 10 
Red clay 50 
Soft gray clay 4 
Gravel and sand; source of water (?) 
Over much of the prairie region there are numerous small spheroidal 
mounds which are rarely more than 2 feet high and 50 feet across the 
base. They are different from the larger mounds of undoubted human 
origin. The origin of these mounds has been a great mystery to all 
those who have studied them. By some they are thought to have 
been built by Indians, others have considered them to have been built 
by ants, and still others have attributed their origin to natural 
agencies, as winds and waves. 
CLAY' INDUSTRY. 
Common building bricks are made at Devall Bluff. The Devall 
Bluff Brick and Tile Company manufactures a stiff-mud side-cut brick. 
The bricks are made from the red surface clay. They will check when 
48130— Bull. 351—08 11 
