206 
THE CLAYS OF ARKANSAS. 
Wb,erever the shales are exposed they rapidly disintegrate and 
form a stiff clay, having approximately the colors of the shales from 
which the clay has been formed. 
The following is a section at Doyle's paving-brick factory : 
Section at Doyle's paving-brick factory . 
Feet. 
Red sandy clay containing waterworn pebbles in considerable 
quantities - - 2 
Blue and black shales interstratified and inclosing some thin beds 
of red arenaceous shale 25 
Sandstone at the base. 
In this section the gravel and clay overlying the shales have par- 
tially obstructed the work of disintegration, so that the shales have 
not yet completely disintegrated. The softer blue shales have for 
the most part disappeared in the clay, but the harder black and red 
shales still remain in their shaly form, although somewhat soft and 
easily crushed. 
Wherever the shales have been exposed by the removal of the 
overlying sandstones and gravel they readily lose their shaly char- 
acter and assume the condition of a plastic clay, having the color and 
position in the series of the shales from which they are derived. 
At Harding & Boucher's quarry, 1J miles south of Fort Smith, in 
the northwest corner of the SW. \ sec. 28, T. 8 N., R. 32 W., the 
surface material consists of about 6 feet of disintegrated shales, 
which rests on the sandstone of the quarry. These shales have 
disintegrated and formed a gray mottled clay. In the lower part of 
the bed the disintegration is not always complete and fragments of 
shale are scattered through the clay. Analyses of these clays and 
shales are given below. 
The shales exposed along the Missouri Pacific Railway track 
through the SE. \ sec. 20, T. 8 N., R. 32 W., are in the same disinte- 
grated and clayey condition as those seen higher up the hill at 
Harding & Boucher's quarry. 
Analyses of argillaceous shales from Fort Smith. 
[Specimen dried at 110°-115° C Brackett & Smith, analysts.] 
Silica (Si0 2 ) 
Alumina (AI2O3) 
Ferric oxide (Fe20 3 ) 
Lime (CaO) 
Magnesia (MgO) 
Potash (K 2 0) 
Soda (Na 2 0) 
Sulphur (S) 
Loss on ignition (water) 
Nigger 
Hill. 
Sand in air-dry specimen. 
Water at 110°-112° C 
58,43 
22.50 
!32 
1.14 
2.18 
1.03 
.16 
6.87 
100.99 
25.72 
3.37 
Harding & Boucher's quarry. 
57.10 
23.74 
8.18 
.53 
1.04 
1.53 
.87 
7.21 
100. 20 
76. 40 
4.24 
65.12 
19.05 
7.66 
.34 
.31 
1.23 
.85 
11' 
42.12 
18.84 
26.35 
.28 
.74 
1.10 
1.85 
8.77 
100. 68 
21.88 
4.79 
100. 05 
None. 
3.19 
