SOUTHERN PACIFIC LINES 133 
beds of limestone. Farther north is Organ Mountain, which, like 
the Cerro de Muleros, consists mainly of a great mass of porphyry 
intruded into the sedimentary strata. The central part of this 
igneous mass presents a massive columnar structure with spires having 
the appearance of huge organ pipes. The limestone into which this 
porphyry has been intruded has been greatly mineralized in places, 
notably at the Stevenson mine, east of Las Cruces, which has been a 
producer of silver and other ores for many years. Various rare min- 
erals occur at this place. Up the valley is seen the winding ribbon of 
the Rio Grande, bordered in large part by irrigated fields. About 
40 miles north, near Las Cruces, is the Mesilla Valley (may-see’ya), 
where a large amount of land is under intensive irrigation, utilizing 
water conserved by the Elephant Butte Reservoir, 115 miles above 
EI Paso. 
From Strauss siding the railroad goes northwest over the wide 
alluvial plain that extends entirely across the southwestern part of 
New Mexico. This plain is characterized by vast numbers of a 
species of yucca (pl. 20, A) with shaggy trunk and a cluster of white 
flowers, which finds the sandy soil favorable for its growth. 
plant, locally known as soapweed or palmilla, yields a valuable fiber. 
and its roots, known as amole, are used as a substitute for soap. The 
datelike fruit is greatly relished by cattle. The northerly trend of the 
railroad in this area is taken to avoid the large rugged area of volcanic 
rocks of the West Potrillo Mountains and its extension to the north. 
The thick body of sand and gravel underlying the plain has been 
drilled for water at several points along the railroad. A boring at 
Lanark passes through 950 feet of beds, all supposed 
ie ce ee be valley fill but possibly including some under- 
Population 40.* lying Tertiary or Cretaceous strata. It found water 
So Orleans 1,214 which rises approximately to the level of the bere in 
the Rio Grande Valley, 15 miles east. A boring 
Kenzin, several miles beyond Lanark, passed through 550 feet of clay 
and sand with water in its lower part and continued through rock 527 
feet farther. 
Beyond Rutter siding great lava fields are in sight to the south- 
west, and near Afton and Kenzin sidings the tracks skirt the edge 
of a fresh recent-looking lava flow (pl. 19, A), which came from two 
conical craters plainly visible to the south and southwest. 
Lanark. 
% According to the United States 
sonry. L 
up the valley with an average width 
1% miles and a capacity of 2,638,000 
acre-feet. It holds the floods of the 
Rio Grande and conserves the water 
for use when needed for irrigation all 
along the valley in southern New Mex- 
ico, western Texas, and i 
