THE SANTA FE ROUTE. 149 
troublesome to the railway company, which must make long deflec- 
tion ditches and dikes to prevent serious washouts. Work of this 
sort along the Santa Fe lines in the desert region has been as large 
an item of expense as flood protection and repair in regions where 
there are large rivers subject to freshets. The run-off is very rapid 
‘in the deserts, because the rocks are bare, the soil is hard, and most of 
the slopes are steep. Very little water passes underground, and ~ 
springs, even in the mountains, are exceedingly rare. Much water, 
however, is lost by evaporation. 
Fenner is on a desert plain or flat-bottomed valley of consider- 
able width. (See Pl. XX XIX, p. 150.) A few miles to the east rises 
the high mountain range which begins at Goffs and 
extends far to the south. Its higher part, southeast 
Pauitarcocea. Of Danby, is known as Old Woman Mountain. This 
range consists largely of granites but also includes 
some limestone which has been mostly altered to marble by the 
intrusion of igneous rocks. The heat and pressure of these intrusions 
are the agencies which have effected this change. The process is 
one of crystallization, the massive or earthy limestone changing into 
an aggregation of crystals, usually white, to form marble. 
The prominent range known as the Providence Mountains, west 
and northwest of Fenner, consists of a thick mass of limestones and 
other sedimentary rocks (Cambrian, Devonian, and Carboniferous) 
lying on granites and cut by thick bodies of monzonite and rhyolite. 
These mountains are the south end of a great north-south divide 
which separates the Las Vegas and Colorado valleys on.the east from 
the deserts on the west and which in general seems to be an impor- 
tant but little understood geologic boundary in this region. In its 
northern extension, known as the Charleston Range, near Good 
Springs, there are rich mines of lead and zinc, and a remarkable 
deposit of gold, platinum, and palladium ore has recently been dis- 
covered. The range contains also interesting stratified formations 
not found to the west in southern California. The southwestern 
course of the railway from Needles to Cadiz was determined for the 
purpose of paralleling the east side and getting around the south end 
of this range, which is reached at Cadiz. 
The basin about Fenner is probably underlain by later voleanic 
rocks, portions of which protrude above the plain in many small 
buttes. One of these is a mile northeast of the station, and a group 
of them occurs about 10 miles due west of Fenner. They consist 
of rhyolite, a fine-grained brown glassy-looking rock, much of which 
contains cindery fragments and many vesicular cavities caused by the 
steam included at the time of outflow. In the midst of these rhyolite 
hills, 10 miles west of Fenner, there is an outcrop of pure white marble 
which some time may have economic importance. 
Fenner. 
