214 
THE CLAYS OF ARKANSAS. 
up a larger trade in clay products in the South and Southwest ought 
to lead to the early development of such industries at some point in 
Sebastian County. 
Chemical analyses of the argillaceous shales show them to be clays 
so far as their chemical composition is concerned. They have been 
changed, however, by pressure and time in physical appearance and 
character. The chemical composition of these clay shales of Sebas- 
tian and adjoining counties suggests the possibility of using them, 
when ground and washed, for the manufacture of the common grades 
of pottery. The clay shales have the average composition shown in 
the table below. For the purpose of comparing this with the pottery 
clays of the Tertiary region of the State (Benton, Perla switch, etc.) 
the average composition of the latter is given in an adjoining column. 
Analyses of clay shales and of Tertiary pottery clays. 
Clay 
shales. 
Tertiary 
pottery 
clays. 
Silica (Si0 2 ) 
Alumina ( AI2O3) , 
Iron (ferric) oxide (Fe 2 0;;) 
Lime (CaO) 
Magnesia (MgO) 
Potash (K 2 0) 
Soda (Na s O) 
Water (H^O) 
58. 91 
22. 21 
7.64 
.53 
1.37 
2.15 
.93 
6.64 
68. 20 
21.79 
1.77 
.20 
1.12 
1.16 
6.44 
The clay shales contain a somewhat higher percentage of the bases 
(iron, lime, magnesia, potash, and soda), elements which increase the 
fusibility of the material, and a lower percentage of silica. The 
higher percentage of iron in the clay shales would give the pottery 
made from it a dark color like that of sewer pipe, but this objection 
would not apply seriously to jugs and many other articles. The 
upper weathered portions of the beds can be ground more readily, 
while the already decomposed and plastic clays that usually cover 
the exposed surfaces of these shale beds may advantageously be 
mixed with the crude material. 
BRICK PLANTS. 
Paving bricks. — It is only since 1889 that the manufacture of pav- 
ing brick has been carried on at Fort Smith. Mr. W. A. Doyle had 
the first contract for the paving of Garrison avenue, and 3,000,000 
bricks were required for this purpose. The bricks were made from 
the disintegrated shales found on Towson road between Towson and 
Wheeler avenues. The shales were ground before pugging. For this 
purpose a Penfield crusher was used. The clay was then pugged in a 
No. 10 D pug mill, and the bricks were made in a No. 20 B Penfield 
machine having a daily capacity of 50,000 bricks. The machinery 
was driven by steam power. The bricks were end cut and dried in a 
