216 CEMENT MATERIALS AND INDUSTRY. [bull. 243. 
Analysis of Selma limestone from locality north of Macon, Miss. 
Silica (Si0 2 ) 8.52 
Alumina (A1,0 3 ) \ 6. 60 
Iron oxide (Fe 2 3 ) J 
Lime carbonate (CaC0 3 ) 83.88 
Magnesium carbonate ( MgC0 3 ) 00 
Water * LOO 
Farther south, along- the Macon and Columbus road, the limestone 
begins to show in every gully and on every hillside. At some places 3 
on level ground the soil is not over 12 inches deep. In this vicinity are! 
the bald prairies, where large areas of this white limestone are exposed 
without a particle of soil or a blade of grass. . A sample of the rock! 
was taken 3 miles north of Macon. 
A sample of Selma limestone was taken at a point north of Lime 
Rock, 5 miles east of Shuqualak, on Oaknoxubee River, where a bluff 
50 feet high is composed of typical Selma chalk. The following anal- 
ysis of this sample was made by W. S. McNeil, in the laboratory ofl 
the United States Geological Survey: 
Analysis of Selma limestone from near Shuqualak, Miss. 
Silica ( SiO, ) 8. 06 
Alumina ( A1 2 3 ) \ 5. 94 
Iron oxide (Fe 2 3 ) '. / 
Lime carbonate (CaC0 3 ) 84. 61 
Magnesium carbonate (MgC0 3 ) 06 
Water 1 . 32 
The Tombigbee River at Columbus has cut its channel into the Eutaw 
sands, forming a bluff on the east side 90 feet high. The material' 
composing the bluff here is a sand that is greenish when wet and gray 
when dry. It contains a small amount of lime carbonate. At the 
upper part of the bluff the sands are of lighter color, and at the top 
are of a light golden yellow. This was the color of sand when depos- 
ited, and is not due to oxidatipn. Numerous little branching concre- 
tions, which are perhaps some kind of badly preserved fossils, occur 
in the lower portion near the water. The upper part of the sands 
contain two species of large oysters, which also occur in the Selma. 
The river at the town is now hugging the east bluff, and the bottom, 
which is 3 miles wide, is all on the west side. A short distance above 
the town, however, the reverse is true, the bluff being on the west 
side and the bottom on the east. 
At the west edge of the bottom the heavy, black prairie soils of the 
Selma chalk appear as soon as the little hills are reached. The bottom 
extends northward to the little creek that flows northeastward into the 
river 3 miles above the town. 
At a distance of 4 miles above town the bluff on the west side of the 
river reaches about the same height above the stream as the bluff at 
