SOUTHERN PACIFIC LINES 59 
sand is coarser and less pure it is adapted to the growth of some kinds 
of garden truck. The Carrizo sand is the underground reservoir that 
furnishes the water to irrigate many fields and gardens, notably in 
the Winter Garden area of western Dimmit and Zavala Counties and 
in the extensive trucking district south of San Antonio, particularly 
the strawberry farms near Poteet, in northern Atascosa County. In 
the Winter Garden area, where the annual rainfall is less than 25 
inches and the native vegetation was mostly mesquite and nopal, 
irrigation by water from the Carrizo sand has made a garden spot 
that abundantly justifies the name. 
Along the Southern Pacific Railroad the Carrizo outcrop is a 
rather monotonous belt of sand and scrubby oak extending from a 
point just west of Harwood to and beyond Ivy siding. Iron Moun- 
tain, one of the higher hills, consisting largely of hard brown sand- 
stone, causes a deflection of the railroad to the north for some distance 
east of Ivy siding, beyond which it passes onto the outcrop zone of 
the Indio lecsinaction! There are fine exposures of the basal sandstone 
of the Carrizo in the cut through the divide a mile west of Ivy, which 
reveals about 30 feet of coarse, mostly soft massive sandstone con- 
taining considerable ironstone and notably cross-bedded. 
These beds are underlain by a thick body of softer sandstones and 
clays of the Indio formation. This constitutes the surface of a wide 
area about Luling, where, however, the strata are 
Luling. mostly covered by alluvium, especially in the flat 
oe that extends west to the San Marcos River. 
New Orleans 517 miles. ‘The outcrop of the Indio formation is wider along 
the Southern Pacific Railroad than that of any other 
of the Tertiary formations, largely because the railroad crosses it 
diagonally in the northerly bend near Luling and also in the south- 
ward deflection of the tracks west of that place. Most of this out- 
crop zone is gently rolling and rather featureless, though it presents 
the threefold division of a lower and an upper clay and shale series, 
locally of marine origin and fossiliferous, separated by nonmarine 
sands and sandy shales. ths soils of the Patio formation vary with 
the lithology. Some of the Imost as sandy, th 
as the Carrizo sand; bars are almost as. heavy and black as the 
Midway soils; but most of them respond to cultivation. Blackjack 
oak and post oak are the common trees on the more sandy soils, and 
mesquite predominates on the clay soils. 
The large “tank farm” of the Magnolia Petroleum Co., a mile east 
of Luling, indicates the proximity of the Luling oil fields. Before the 
discovery of petroleum here in August, 1922, Luling was a small, easy- 
going German community, concerned chiefly with the price of cotton, 
on which the material welfare of the inhabitants depended. The 
