A 
78 CEMENT MATERIALS AND INDUSTRY. [bull. 2 
which, i»i descending order, are (1) the Upper or Salt Mountain di\ 
sion, observed at one locality only in Clarke County, (2) the Midd 
or St. Stephens division, and (3) the Lower or Jackson division. ( l( 
these it is only the St. Stephens limestone with which we are he 
concerned, since the first is, as far as known, restricted to one localit < 
and the third is seldom exposed along* Alabama rivers and railroad 
The following section of St. Stephens Bluff, Tombigbee River, w 
give an idea of the strata of this division: 
Section of St. Stephens Bluff. 
Feet 
1 . Red residual clay 1 to 
2. Highly fossiliferous limestone hold ingmainly oysters, and full of holes, 
due to unequal weathering „„ 10 to 
3. Orbitoides limestone (chimney rock), a soft, nearly uniform porous lime- 
stone, making smooth perpendicular face of the bluff except where 
bands of harder limestone of very nearly similar composition alternate 
with the softer rock. Both varieties hold great numbers of the circu- 
lar shells of Orbitoides mantelli. These harder ledges are nearly pure 
carbonate of lime, take a good polish, and are often burned for lime... 
4. Immediately below 3, for 5 or 6 feet, the strata were not visible, being 
hidden by the rock falling from above, but the space seems to be occu- 
pied by a bluish clay. Then follows a soft rock somewhat of same 
consistency as No. 3 above, but containing a good deal of greensand. 
The fossils are mostly oysters and Plagiostoma dumosa. This bed is in 
places rather indurated superficially, and forms projecting ledges 10 to 
5. Bluish clayey marl with much greensand, containing the same fossils as 
No. 4. It washes or caves out from under No. 4, which overhangs it.. 4 to 
6. Massive joint clay, yellow on exposed surface, blue when freshly broken; 
no fossils observed. Extends below the water level to unknown 
depth; exposed 3 to 
The rock of this formation, which seems to be the best suited f< 
cement material, is the soft " chimney rock" or Orbitoides limestor 
of bed No. 3 above. This is usuall} 7 quarried for chimneys and othcjj 
constructions by sawing it out and dressing it down with a plane inljt 
blocks of suitable size, which are then laid like brick. 
The numerous analyses given below will show that this rock id 
purer limestone than most of the material of the Selma chalk of til 
Cretaceous formation above considered. In cement making it will, j 
consequence, require a larger proportion of clay to be mixed with i 
and the question of obtaining suitable clay in sufficient quantity am 
in close proximity becomes one of some importance. The residuj 
clay left after decomposition and leaching of the limestone seems t 
be fairly well adapted to the purpose. Besides this residual cla}^ somi 
analyses have been made of the clays of the river and creek bottom 
of the country near the limestone outcrops, and of the clays of thi 
Grand Gulf formation, which very generally in this section overlie 
the limestone. Some analyses of the last-named clays have been mad 
from material occurring near St. Stephens, and near Manistee J un< 
