210 THE CLAYS OF ARKANSAS. 
to show the origin of the residuary pottery clays rather than to 
explain the presence of clay at a single locality. Throughout the 
entire county the rocks are thrown into folds and eroded, and wher- 
ever the argillaceous shales are exposed to decomposing agencies 
they have been changed into plastic clays. 
In searching for the clays, or the clay shales from which they are 
derived, one must keep in mind the structural features of the region 
and the agencies by which the clays are produced and modified. It 
should not be forgotten, however, that sedimentary rocks frequently 
change in character in passing along the outcrops, so that what is a 
sandstone at one place may be an arenaceous shale at another and an 
argillaceous shale at a third locality. 
The upland clays of Sebastian County are confined to the region of 
Paleozoic rocks. These clays, however, are not all produced by 
decomposition directly from the argillaceous shales. Some of them 
have been washed into the valleys and, mingled with the residual 
rocks of the region, have formed "buckshot clays" by precipitation 
within them of the iron carried in solution by percolating waters. 
The method by which these clays are formed is described in Chapter 
II of this report. These "buckshot clays" are not available for 
the manufacture of pottery, but they are used more or less for making 
bricks. 
comby's clays. 
The clay formerly used at Comby's pottery is a light-yellowish 
surface clay, found in a low-lying piece of ground in the S. J SE. \ 
sec. 27, T. 7 N., R. 30 W., where it has a depth of about 2J feet. The 
mode of origin of this clay has already been described. 
Analysis of Comby's pottery clay. 
[Brackett & Smith, analysts.] 
Silica (Si0 2 ) 81. 61 
Alumina (A1 2 3 ) . . : 10. 52 
Iron (ferric) oxide ( Fe 2 3 ) 2. 70 
Lime (CaO) 32 
Magnesia (MgO ) 40 
Potash (K 2 0) 66 
Soda (Na 2 0) 57 
Manganese (MnO ) Trace. 
Water (H 2 0) 3. 95 
100.73 
Water at 110°-115° C 3. 86 
Fine sand 18. 43 
The ware from this clay is of poor quality and consists chiefly of 
such articles as are in local demand, such as churns, jugs, crocks, and 
jars. No other kinds of ware have been manufactured. It can not 
be said that this clay has been so tested as to establish or disprove 
its availability for the manufacture of pottery. 
