OF ARKANSAS. 113 
with iron ore, is a variegated shale, on the exposed surface of which numer- 
ous crystals of selenite or sulphate of lime are forming, no doubt, from the 
mutual action of protosulphate of iron and bi-carbonate of lime; giving 
rise to sulphate of lime and protocarbonate ofiron. This may be the origin, 
too, of this latter mineral, so abundantly found in the underlying black 
shale. The production of the protosulphate of iron, implicated in this 
mutual decomposition, is evidently to be accounted for, at this locality, by 
the gradual oxidation of sulphur and iron, the elements of iron pyrites, 
abundant, even now, in these shales, and, no doubt, more so at a former 
period, before the production of the above minerals. 
This gypsiferous shale would, undoubtedly, prove to be a valuable min- 
eral manure, applied to some of the siliceous soils, overlying the sand- 
stone formations of this country, as well as to those located at the base of 
the sandstone ridges, which have received the sandy debris washed from 
their flanks. 
The strata concealed in the slope above these shales, exposed both at 
the Lick and on the Town branch, are, most probably, a continuation of 
similar shales, underlying the Archimedes limestones, such as were after- 
wards seen under that rock elsewhere in the county, as will appear in the 
subsequent part of this section. 
The shale beds, partly exposed in the drain below Cato’s spring, proba- 
bly overlie the Archimedes limestone; this member includes a seam of 
coal of one or two inches, of no practical value. The eight inch coal, 
which has been partially opened for the use of the blacksmiths, lies higher 
up in the hills, in shales, above the pentrimital limestone, at Cato’s spring, 
over which is the main body of sandstone, forming the upper part of the 
ridge southeast of Fayetteville, including one or more calcareous bands. 
On the Town branch, on section 20, township 16 north, range 30 west, 
about 20 feet of black shale are exposed, similar to that at the Lick, one mile 
west of Fayetteville; the former shale contains large septaria, both of 
carbonate of lime, and carbonate of iron. 
