SEBASTIAN COUNTY. 207 
The Xigger Hill shale is from the paving-brick kiln of W. A. Doyle 
on Towson road, Fort Smith; the other three are from Harding & 
Boucher's quarry in the northwest corner of the NW. \ sec. 28, T. 8 N., 
K. 32 W. Sample 2 is from the gray clay about 3 feet below the 
surface; sample 3 is from the yellow mottled with red; and sample 
4 is from the undecomposed shale next to the sandstone beneath. 
It is not possible to specify all the places at which clay shales 
available for the manufacture of bricks, sewer pipe, and similar 
products may be found in Sebastian County. They are associated 
with the coal at many 'places in the coal mines. Many of the clays 
that lie immediately beneath the coal are available as fire clays. 
A specimen of gray clay from KcKenna's quarry, near Hackett 
City, was sent in by Mr. Ed. McKenna. The analysis is given below. 
Analysis of gray clay from McKenna 's quarry, at Hackett City. 
[Material dried at 110°-115° C. R. N. Brackett, analyst.] 
Silica (Si0 2 ) 54. 13 
Alumina ( A1 2 3 ) '. 30. 69 
Ferric oxide (Fe 2 3 ) 3. 15 
Manganese oxide (MnO) Trace. 
Lime (CaO) 63 
Magnesia (MgO) 94 
Potash (K 2 0) 49 
Soda (Na 2 0) 2. 01 
Loss on ignition 8. 54 
100. 58 
"Water at 110°-115° C 4. 82 
At the Hartshorn coal mine, 4 miles south of Fort Smith, is a bed 
of dark-gray shale 4 feet thick. A sample was sent to the Survey 
by Mr. W. A. Doyle, of Fort Smith, and analyzed, with the results 
given below. The relation of this shale to the coal at the mine is 
not stated. 
Analysis of shale from the Hartshorn coal mine. 
[Material dried at 110°-115° C. R. N. Brackett. analyst.] 
Silica (Si0 2 ) 70. 83 
Alumina (A1 2 3 ) 17. 49 
Ferric oxide (Fe 2 3 ) 3. 64 
Magnesia ( MgO) 91 
Potash ( K,,( ) ) 25 
Soda (Na 2 6) 1. 72 
Loss on ignition 4. 95 
99. 79 
"Water at 110°-151° C 76 
The region about Mansfield may be taken as a type of the topog- 
raphy and geology of most of the country south of Fort Smith. The 
