SOUTHERN PACIFIC LINES 247 
traffic of Imperial Valley. This sand-dune belt is one of the largest 
inland occurrences of its kind in the United States. Doubtless the 
dunes are still shifting somewhat, but as land surveys of 1856 show 
practically the same configuration as the present one, the change 
must be slow, and probably many hundreds of centuries has been 
required for their accumulation. They are a serious barrier to canal 
construction, as the sand is loose and drifts extensively, but in 1931 
provision was made to build an all American canal through them to 
supply water to Imperial Valley without the deflection into Mexican 
territory which the old canal makes. 
From Ogilby northwestward the railroad passes between the sand- 
hill belt and the long slopes that lead up to the mountains to the 
northeast. At Glamis a road to Blythe leaves the 
railroad and proceeds to a distant pass up the Palo 
Verde Valley (pah’lo vare’day), a wide dry wash 
which rarely carries any water. As the rainfall in 
this region is very low, an average of about 3 inches a 
year, vegetation is sparse and closely adjusted to soil conditions. 
Ironwood (Olneya tesota) and the creosote bush (Covillea) are the most 
noticeable features in the vegetation; ocotillo is conspicuous in places. 
Some of the ironwoods are 20 feet high, but they are widely separated. 
Northwestward from the gap northeast of Glamis the Chocolate 
Mountains” make a high continuous wall extending for 20 miles as a 
succession of prominent ridges rising abruptly from the valley, 3 to 8 
miles northeast of the railroad. In these mountains there have been 
a few notable mines, including the Paymaster and Pegleg, both of 
which were good producers of silver-lead ores years ago. At the east 
end are some outlying buttes capped by basalt, and in part of the 
range and in foothills on its south side are andesitic and rhyolitic 
lavas of Tertiary age. It has been suggested that the steep south 
front of the range in this vicinity was determined by a te granite 
and basalt occur in small foothills south of the main rang 
On the south side of the railroad is the great sand-hill | belt (see pl. 
36, A), on the farther side of which is Imperial Valley. 
There is a down grade from a point near Glamis westward, and the 
tracks pass below sea level near Flowing Well siding. This place 
7 The Chocolate Mountains con- | the canyon leading to this pass beds of 
sist mainly of granite, but schist also | white soft tuff give place to a vertical 
occurs, and these old rocks are over- | mass of dark rhyolitie breecia in which 
lain ee lavas 
of Tertiary age. In Iris Pass, which 
Glamis. 
Elevation 338 feet. 
Population 15.* 
New Orleans 1,785 
mniles. 
In 
crosses the range north of Niland, there 
of stee 
and yellow clay, lyi 
igneous rocks. Near a upper end of 
ate which appear to 
zontal and contain boulders of rhyolite 
and other volcanic rocks. West of the 
pass granite is the principal rock, con- 
stieetinare high rocky range. (Brown.) 
