154 THE CLAYS OF ARKANSAS. 
elevation of the town at the foot of the ridge. The following is a 
section of the hill along the road leading east from the town: 
Section of Crowleys Ridge at Harrisburg. 
Feet. 
Yellow clay (Columbia) on top of ridge 30 
Stratified sand, variegated in color, interbedded with gray joint 
plastic clay 65 
Unexposed detritus to foot of hill 12 
A record of one of the wells in the town at the foot of the ridge 
gives the following section: 
Section of well in town of Harrisburg. 
Feet. 
Red to yellow clay, with some gravel 40 
Blue gumbo clay free from sand, with small vein of water on top. . 25 
Very fine red dry sand, which caves badly 40 
Dark-blue or slate-colored sandy clay, containing small fragments 
of leaves, shells, and rotten wood; gives bad odor to water 50 
Blue sand, water bearing 30 
CLAY DEPOSITS. 
The surface clay, which is 40 to 50 feet thick at foot of the ridge 
at Harrisburg, is only about 10 feet thick at L'Anguille River, 4 
miles west of town. It changes from a reddish yellow at the foot 
of the ridge to white at L'Anguille River. In places it forms buck- 
shot soil. 
The surface yellow clay on the top and sides of the ridge, and 
also the surface clay in the lowlands as far west of L'Anguille River, 
are well suited to the manufacture of common wet or stiff-mud and 
dry-pressed bricks. The blue Tertiary clay that outcrops well up 
on the side of the* ridge would, with proper manipulation, doubtless 
make an excellent face brick. The following analyses are made 
from brick clay at Harrisburg, Poinsett County: 
Analysis of brick earth from the surface, Harrisburg. 
[Dried at 110°-115° C. Brackett & Smith, analysts.] 
Silica (Si0 2 ) 81. 79 
Alumina ( A1 2 3 ) 9. 37 
Iron oxide (Fe 2 3 ) 4. 03 
Manganese (MnO) Trace. 
Lime (CaO) 31 
Magnesia (MgO) 38 
Potash (K 2 0) (by difference) 8G 
Loss on ignition 3. 26 
100. 00 
Air-dried sand in air-dried clay 30. 92 
