62 GUIDEBOOK OF THE WESTERN UNITED STATES 
ature in mines and borings is found to increase with depth at an aver- 
age rate of about 1° for every 60 feet, below the first few feet. In 
two 2,250-foot holes near Luling the temperature was found to be 
120°, which indicates a rate of increase of 1° in slightly less than 45 
feet. At Pierce Junction, near Houston, the temperature in a 3,300- 
foot hole was 130° and in a 4,303-foot ai 146°.? 
The San Marcos River, which is crossed 3 miles west of Luling, has 
its principal source in the great springs at San Marcos, 30 miles 
northwest, at the foot of the Edwards Plateau. (Turn to honed 9.) 
West of the San Marcos River the railroad passes over a wide 
lowland of the Indio formation to a point beyond Sullivan siding, 
where it ascends about 100 feet onto a high terrace. 
Kingsbury. This terrace is underlain by the Indio formation but 
Popaietear wer? covered and preserved by a compact deposit of gravel 
New Orleans 528 miles. aNd sand carrying much chert evidently derived from 
the Edwards Plateau. This deposit extends north 
of the railroad for some distance as a cap on the Mill Creek Hills and 
undoubtedly was originally deposited by an earlier San Marcos River 
in late Tertiary time.“ In the descent off this terrace west of Kings- 
bury there are exposures of the Indio formation, mostly soft sandstone 
and a few hard layers. Beyond this down grade is a wide lowland 
extending to Seguin (say-gheen’). 
Seguin is on the alluvial plain of the Guadalupe River, here under- 
lain by lower shaly beds of the Indio formation. It is a prosperous 
town, with cotton mill, sugar refinery, and various 
other industries. Water power is generated from the 
Guadalupe River a short distance north of the town. 
Wee Ovlaus tie sees Seguin was founded while Texas was a republic and 
was named from two Spanish settlers who lived in the 
vicinity during the stirring days of the Texas revolution. One was 
Don Erasmo Seguin, of San Antonio de Bexar (bay’har), who had a 
share in creating the constitution of Texas, and the other Juan Seguin, 
who commanded a small body of Mexicans who fought effectively 
under General Houston in the battle of San Jacinto. 
A gravel pit about 2 miles west of Seguin, south of the railroad, 
shows about 10 feet of gravel grading up into sand, the upper part of 
Seguin. 
Elevation st feet. 
® Hawtof, E. M., Am. Petroleum 
Inst. Bull. 205, Pr. 62-108, 1930 
® Most of aetna hey divides 
on the = Thetis portion of the Coastal 
Plain are capped by gravel deposits 
of this character. are remnants 
of an old surface, called the Uvalde 
plain because it is very extensive i in the 
Uvalde region. has been 
Mrgety soeored bY streams, which in 
deep, many il them along courses 
differing materially from the drainage 
ways that crossed the old Uvalde sur- 
face. Notable remnants of this plain 
remain Antonio and south 
poe tere New Braunfels, San Marcos, 
and A 
