SOUTHERN PACIFIC LINES 257 
north and is maintained by the impervious cover of fine-grained de- 
posits which occupy the center of the basin. The water is derived 
from rainfall on the mountains and higher slopes, which passes under- 
ground in the coarse material extending as alluvial fans along the foot 
of the mountains. Most of the water falling on the mountains runs 
off the hard rocks and steep slopes but is absorbed by the gravel and 
sand of the valley fill. Several streams, such as Whitewater Creek, 
Snow Creek, Tahquitz Creek, Andreas Creek, and the creek in Palm 
Canyon, sink in that way. In the northern portion of the valley the 
underground water is of excellent quality, containing only from 150 
to 250 parts per million of mineral constituents, but south of a line 
from the south end of the Santa Rosa Mountains to Salton siding the 
waters are too saline for use. 
The underground water supply about Indio and southward to 
Mecca is limited in amount, but about 16,000 acres is being irrigated. 
The crops include melons, dates, grapes, alfalfa, and many other 
products. The United States Department of Agriculture has made a 
detailed study of the soils of the Indio area, and many experiments 
have been made to determine the best crops and proper conditions for 
their irrigation. Underground waters are pumped at several places 
west of Indio for irrigation and other purposes. Water furnished 
by springs and wells east of Salton siding is of too poor quality for 
irrigation. 
At Mecca (formerly called Walters) the Coachella Valley is a wide 
alluvial flat extending from the foot of the Santa Rosa Mountains on 
the southwest to the Mecca Hills on the northeast. 
The Mecca Hills consist of a 5,000-foot succession of 
poration —1S8 eet. steeply tilted yellowish sandstone and sandy shales 
New Orleans 1,859 with a basal member 1,000 to 1,200 feet thick of 
oa: brownish-red sandstones and conglomerates. These 
rocks are well exposed on the Shaver Canyon road east of Mecca. 
(See also p. 259 and pl. 40,A.) The strata are closely folded, as shown 
in Figure 62. In Burnt Springs Canyon and near Hidden Spring, east 
of Mecca, the anticlinal structure of the front ridge is well shown. 
At Hidden Spring the sedimentary rocks appear to be invaded by a 
mass of rhyolite. At Shaver Well, about 10 miles east of Mecca, a 
mass of old schist is exposed in contact with the overlying conglomer- 
ate and sandstone. To the east of this place are the high ridges of 
dark schist known as the Orocopia Mountains. A sandy strip mark- 
ing the old beach of former Lake Cahuilla is crossed by the highway a 
few miles east of Mecca, before it enters Shaver Canyon. 
About Mecca the principal products of irrigation are oranges, dates, 
and Bermuda onions, which are shipped to all parts of the United 
States. 
Many date palms are growing in the vicinity of Mecca and Indio, 
where the climate and soil seem particularly favorable. Experi- 
Mecca, 
