74 CEMENT MATERIALS AND INDUSTRY. [bull. 24: 
rock shows a tendency to flake off and weather into caves, sometime 
several feet deep and 20 feet or more in length. These holes extern 
in some places for great distances along the bluffs, as on Alabam 
River just above Kings Landing, on the Tombigbee below Roes Bluff 
and at Jordans Ferry. The outcrop of the argillaceous rocks of thi 
division gives rise to black prairie soils, in which beds of fossil sheik 
mainly oysters, are common. 
It has been suggested that the argillaceous rocks of this and th 
uppermost division could be mixed with the purer limestone of th 
middle division in such proportions as to constitute a good cemer 
material. In this case it would be easy to select localities near th 
junction of the two divisions where both varieties of the rock could b 
quarried, if not in the same pits, at least in pits closely adjacent. Thi 
would do away with the need of adding other clay to the limestone 
Localities of this sort would be found along the borders north am 
south of the belt of outcrop of the white Demopolis rock. 
DISTRIBUTION OP SELMA CHALK. 
The general characters of the rocks of this formation have bee 
mentioned above, and it remains to give details of the special localitiei 
examined, together with analyses of the limestones collected. Ii 
making the collections material from the middle division has been gen 
erally chosen, since most of the limestone of the formation whic 
contains 75 per cent or more of carbonate of lime is to be found ii 
this division. At the same time specimens of the more argillaceous 
material, especially of the lower division of the formation, have bee i 
taken for comparison and analysis, in order to ascertain whether 
will be practicable to provide a cement mixture by using the prope I 
proportions of the purer and more argillaceous materials. 
Inasmuch as suitable material for cement manufacture can be had i 
practically unlimited quantity all along the outcrop of the purer limji 
stone of the middle division, the location of the plants for the maim 
facture of this product will be determined by other consideration 
than the quality of the rock. Chief among these will be facilities fct 
transportation, cheapness of fuel, and cost and abundance of label 
Examinations have consequently been confined to those local iti( 
which appear to be most favorably situated in these respects, an h 
especially to those localities which are on navigable streams or c 
north-south railroad lines, or on both. 
The first place considered on Tombigbee River is Gainesville, whei 
the limestone, 30 to 40 feet thick, appears on the river bluff beneath 
heavy covering of sands and pebbles. A short distance from til 
river, however, the rock outcrops at the surface and may be quarriei 
without difficulty. Specimens taken from tiie different parts of trJ 
bluff near the ferry show the composition of the limestone here (sf' 
