168 
STRUCTURAL GEOLOGY 
to the ordinary traveler. Now all is changed and the inconven¬ 
iences of that day are entirely removed. Recent construction of 
a railroad throughout the length of the old lake bottom obviates 
all the insufferable terrors of desert travel. The opening up of a 
new main line of the Los Angeles and Salt Lake road brings to 
hand numberless fine lake features. This main line traverses the 
Toetle Valley, on the west side of the Oquirrh Range of moun¬ 
tains. As the grade cuts into the north end of this range above 
the shore of the present Great Salt Lake a score or more of the 
best preserved ancient beaches on the mountain side are plainly 
visible from the car window. 
In ascending the Toetle Valley thirty miles the road grade 
rises 1000 feet, and deeply excavates the highest Bonneville beach 
at the pass into Rush Valley. The pass is blocked by the great 
Stockton gravel bar, which as it formed, made of the broad bay 
beyond a separate lake of no inconsiderable. dimensions. As 
when Gilbert mapped the region a long spit extends to the south¬ 
ward and around a spur of the mountains and a gigantic bay bar 
stretches out at almost right angles to the spit and reaches west¬ 
ward to a spur of the Aqui Range on the opposite side of the valley. 
For many miles the road-grade follows closely a long line of 
sea-cliffs which sharply mark the highest stage of the old lake. 
At the pass the grade-cutting across the bar follows around the 
margin of the spit for a distance of more than a mile. 
The bay bar is a huge embankment rising 400 to 500 feet above 
the valley floor on either side, and nearly two miles long. It is 
composed of small subequal boulders or large gravel stones. The 
exposures in the gravel pits which the railroad has opened up 
for fillings are 50 feet high and quite uniform in texture. The 
broad flat top marks the old level of the lake waters. On the 
sloping sides of the great bar are numerous minor beaches denot¬ 
ing brief pauses as the lake waters were receding and lowering. 
For a thousand miles the railroad traverses the Great Basin. 
It covers nearly every phase of Gilbert’s work. Along the moun¬ 
tains where faults should be displayed, according to his Basin 
Range theory, deep road-cuttings reveal none. Alleged fault- 
scarps are plainly normal mountain girdling due largely to sand¬ 
blast action, a process of desert erosion unrecognized in Gilbert’s 
time. Many of the so-called sea-cliffs of the Salt Lake desert 
are found to be not such at all, but effects of undercutting by 
