Reco-Rd of Geology of Texas, ISSY-ISOG. 
157 
Hill^ Robert T. 
foTO, into the following artificial divisions for working convenience. 
“ 1 . Northern District, or portion north of the Colorado, including 
24,000 square miles. * "■ 
“The Northern District was chosen as the best adapted for preliminary 
operations, and the work has been confined to that field.” 
A Brief Description of the Cretaceoiis Rocks of Texas and their 
Econoanic [Value] Dses'. Based principally upon a Preliniinary 
Section along the Colorado river from near Sinithwick Mills, Bur- 
net county, to Webberville, Travis county. 
First Ann. Rept. Geol. Surv. of Texas, 1889, pp. 10'3-141. 
Austin, 1890. 
Contents :( Synopsis, ilntroduction. Upper, or iBlaek Prairie series. — 
'Geologic structure of the Black Prairie region ; Lower Cross Timber sands ; 
Eagle Eord clay shales; White Rock or Austin-Dallas chalk; Exogyra pon- 
derosa marls; Upper arenaceous, or glauconitic series. Lower, or Coman- 
che series. — ^Trinity sands, or Upper Cross Timber division; The Freder- 
icksburg division; Basal beds; Comanche Peak beds; iCaprina chalk; The 
/Washita division. — The Flagstones; The Upper Caprotina limestone, or 
Austin .‘Marble; The Washita or Fort Worth limestone; The Exogyra 
Arietina iClays; The Shoal Creek limestone; The Denison beds. Strati- 
graphy of the 'Oomanehe series in general. Progress section. Disturbances 
of the strata. General economic features. 
“The two series of rocks comprising the Cretaceous System occupy the 
area of the State known as the Black Prairie, the Grand Prairie, and the 
two Cross Timbers', and unstudied areas in the eastern and Trans-Pecos 
regions of the State. 
“To these strata the .State owes a large part of her agricultural and 
general priosperity, for they are the foundation of the rich black waxy 
and other calcareous soils of those regions. 
“In addition to their agricultural features they are the most productive 
source of building material, while adjacent to the parting between them, 
extending the entire length of the iState and dependent upon their strati- 
graphy, is a remarkable area of natural and artesian wells, as seen at 
Fort Worth, 'Austin, Waco, Taylor, San Marcos and elsewhere. 
“That these formations are of great economic value to the State is also 
shown by the fact that they are the site of our principal inland cities, 
and the rich agricultural soils which surround them.” Pp. 105-106. 
220 . 
The Eagle Flats Formation and the Basin of the Trans-Pecos 
Region of Texas. (Abstract.)' 
Proc. Amer. Assoc. Adv. of Science, Vol. XXXVIII, p. 242. 
1890. 
“The portion of Texas west of the Pecos river is described as a series 
of complicated mountain disturbances, accompanied by much faulting and 
