II. THE SAN CARLOS COAL FIELD OF TRANS-PECOS TEXAS AND 
ADJACENT PORTIONS OF THE VIEJA MOUNTAINS. 
INTRODUCTORY NOTE. 
In August, 1895, the writer was requested by Mr. Robert T. Hill, 
geologist in charge of the Texas division of the United States Geolog- 
ical Survey, to go to the newly opened coal mines in the vicinity of 
San Carlos, Presidio County, Texas, in order to ascertain the geologic 
position of the coal, and if possible obtain samples of it for the Atlanta 
Exposition. Mr. T. W. Stanton accompanied the writer, for the pur- 
pose of studying the paleontology, and to a large extent the field work 
was carried on jointly. Mr. Stanton furnished the determinations of 
the fossils collected and his conclusions regarding the horizons to which 
they belong. Dr. E. C. E. Lord kindly made a careful study of all the 
lithologic material collected, and the results of his investigations are 
given in his report on the igneous rocks from the vicinity of San Carlos 
and Chispa, Texas, which is a part of this bulletin (pp. 88 to 95). 
While at San Carlos numerous courtesies were received from the 
following officers of the San Carlos Coal Company: Mr. S. A. John- 
son, president; Mr. Charles Seibert, general manager, and Mr. John 
J. Maloney, mine superintendent; also from Mr. G. N. Marshall, chief 
engineer of the Rio Grande Northern Railroad, and Mr. J. E. van 
Riper, civil engineer. To these gentlemen our thanks are extended. 
GEOGRAPHIC POSITION OF LOCALITIES STUDIED. 
(PI. VI.) 
Chispa and San Carlos, the places near which our studies were made, 
are situated in Jeff Davis and Presidio counties, respectively, almost 
in the heart of the mountainous region of Trans-Pecos Texas. Chispa 
is on the Southern Pacific Railroad, about 150 miles southwest of El 
Paso. San Carlos is 26 miles, by rail, almost due south of Chispa, at 
the terminus of the Rio Grande Northern Railroad, a short road 
branching from the Southern Pacific Railroad at the latter place. The 
work on this branch road, which was far advanced at the time the 
region was visited, has been completed. 
Most attention was given to the Vieja Mountains, which are a por- 
tion of a range with a trend from west of north to south of east. 
Beginning at the southern end of this range and going north, it coin- 
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