«'kel.| TEXAS. 307 
cason probably not of importance in this connection. The principal 
(ktcrops of the Tullahoma form the barrens of the highland rim and 
Icur in the counties immediately surrounding the central basin. 
The next division is the St. Louis limestone. This formation covers 
lie higher points of the highland rim and forms the surface rock over 
wide belt of country along the western base of the Cumberland 
ible-land. Livingston, Sparta, Cookevilie, and McMinnville are 
mong the towns located on this belt. Another large outcrop covers 
be greater parts of Robertson, Montgomery, and Stewart counties, 
fhieh adjoin counties in southwestern Kentucky in which the same 
3rmation prevails. The St. Louis limestone is from 200 to 300 feet 
lick and consists mainly of gray and blue, thick-bedded, cherty lime- 
one. Near its base, however, especially in Montgomery County, 
ic formation often includes many beds of high-grade limestone, 
rhere such beds occur they are sometimes underlain by oolitic and 
mioolitic limestone regarded as of the same age as the Spergen 
mestone of Indiana. 
In Tennessee the Chester group consists largely of limestone, which, 
5 it rests directly upon the St. Louis limestone, has been described 
gether with that formation by IIa}^es and others as a single formation 
nder the name Bangor limestone. In his reports Stafford usually 
fers to the Chester as the "Mountain limestone." 
The Chester is limited to the eastern half of the State. It forms 
e base or part of the slopes of the Cumberland table-land on all its 
des. Interbedded with the limestone are numerous beds of often 
ghly-colored shales and several comparatively unimportant sand- 
ones. The shales grow relatively more abundant toward the top 
': the formation. 
PORTLAND-CEMENT RESOURCES OF TEXAS. 
By J. A. Taff. 
PORTLAND-CEMENT MATERIALS. 
A number of limestone formations occur in the Carboniferous and 
der Paleozoic rocks in north-central Texas and in the Trans-Pecos 
gion, and a limestone has also been located near the base of the 
feiary in Limestone County. These limestones may prove to have 
impositions adapted to the production of certain classes of cement, 
it the constituents have not been determined. 
Of the many limestone formations in the geological column of Texas 
ose of widest extent and greatest purity and therefore those best 
iapted for use in making Portland cement are of Cretaceous age. 
| The Cretaceous of Texas occurs in a wide belt of country, extending 
iross the central part of the State in a north-south direction from 
led River to the Rio Grande. It makes the most fertile lands in the 
