YELL COUNTY. 288 
Argenta and at Fort Smith. The same clays occur in Yell County 
in the second bottoms, usually well away from the river. But as the 
Yell County line follows this river for 28 miles, there is an abundance 
of this material in the second bottoms, especially between Darda- 
nelle and the mouth of Petit Jean Creek. Over the pink and yellow 
clays that form most of these terraces lie patches of what the Arkan- 
sas Geological Survey has called chocolate clays. These chocolate- 
colored clays are very fine silts, and are extremely plastic and sticky 
when wet. When dried they often break up in small angular and 
conchoidal fragments and are sometimes called "buckshot" clays, 
not on account of the presence of the iron nodules that characterize 
the true "buckshot" loams, but because it falls to pieces in these 
small lumps about the size of a buckshot. These chocolate clays 
have thus far been found in the State only within the area subject to 
overflow by Arkansas River, and it has therefore been supposed that 
they are silt deposits made by that stream. The section at Johnsons 
Bridge just given shows that the chocolate clay is of later age than 
the yellow and pink loams of the second bottoms. The chocolate 
clay usually contains an abundance of lime nodules. The clay itself 
is also high in lime, as is shown by the following analysis: 
Analysis of chocolate clay from Johnsons Bridge, near Dardanelle. 
[Specimen dried at 1 10°-ll. r >° C. Brackett & Smith, analysts.] 
Silica (Si0 2 ) 50. 91 
Iron (Fe 2 3 ) (i - ,iS 
Alumina (A1 2 3 ) 19. 80 
Lime (CaO) * 4. 7(1 
Magnesia (MgO) 96 
Pol ash (K 2 0) 2. 12 
Soda (Na 2 0) ■ 1. 05 
Loss on ignition 9. 57 
101. 85 
Water at 110°-115° C. 7.77 
A qualitative examination of the nodules in the chocolate clay 
showed that they consist chiefly of lime carbonate, but they contain 
considerable iron and magnesium. 
The chocolate clay overlying this yellow sandy clay at Johnsons 
Bridge and elsewhere in the neighborhood has been tried for brick- 
making, but without success. Indeed, it may be set down as a rule 
that the chocolate clay, wherever found in the State, is unsuited to 
brickmaking. 
a Some of the lime is in the form of carbonate, but the carbonic acid was nol determined. 
