Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

MOJAVE RIVER- WRtM SPRING-SALT.
and barley had been harvested, and I reached the canon about dark. I travelled onwards in the
dark, keeping the trail as well as possible, until late in the night, when the noise of mules was
heard, and soon afterwards the teamsters' camp was found. Mr. Smith had camped beyond.
My mule was soon picketed, and rolling myself in a blanket I slept until daylight.
November 7.-In the morning everything was enveloped in a thick fog, so dense that objects
could not be seen at a distance of twenty or thirty feet. The amount of water precipitated on the
trees and shrubbery was enormous, although it did not rain. The elevation of this part of the
pass is over 3,000 feet. As the wind arose, the fog rolled upwards towards the summit and
permitted the surrounding ridges to be seen. Reached the depot camp, on the Mojave, in the
afternoon. The water at the spring is much warmer than the air; its temperature was found
to be 73~, and the air 60~ F.
November 8.- At daylight this morning the ground was covered by frost. Temperature
of the air 34~, water of the spring 72~. Diameter of the basin of the spring about twenty
feet; depth one foot to eighteen inches; sandy bottom. The soil at camp was very light and
d u s t y and looked lik e dry ashes. It was composed chiefly of clay and sand. In some places
there was a thick growth of " salt-grass" and efflorescenses of salt were seen. A sample of
this soil was taken, (No. 264 of the collection.) On examination it was found to effervesce
strongly with dilute acid; th e aqueous extract contained Chloride of Sodium.
Carbonate of Soda.
Sulphate of Soda.
Sulphate of Magnesia, (little.)
At the breaking up of the depot camp, and the division of the party, I acccompanied Lieutenant Parke with the train of wagons to the Cajon Pass and through it to San Bernardino.
CAJON PASS.
This pass has been known and much used for many years, being the point where the old
Spanish trail from New Mexico to California reaches the settlements of the coast. It has been
called El Cajon de los Mejicanos, but is now well known simply as the OCajon.
It leads from the valley of the Santa Anna, over the Bernardino mountains, to the surface of
the Great Basin, near the sources of the Mojave river. It crosses the Sierra at one of its lowest
points in that vicinity, but its summit is more elevated than either of the other passes
through this chain, being 4,676 feet -above tide, while Williamson's Pass is 3,164 and the
Pass of San Francisquito 3,445.
This pass presents one great peculiarity-the surface of the Great Basin forms its summitlevel-and the traveller, when approaching the pass over the slope of the Basin, which is so
gentle as to seem like a level plain, finds himself at the summit-level of the pass, without
having encountered a single ridge. This peculiar configuration of the surface is well show by
the profile of the pass and is considered at greater length in the chapter devoted to the description of the Great Basin. The following observations on the geology of the pass were made in
succession from the summit or margin of the Great Basin downwards towards the valy of San
Bernardino.
By reference to the Geological Map, the relative position of this pass to others and a general
view of its geology may be at once obtained. The high ridges which bound it on each side are
granitic, and at the margin of the Great Basin they separate, so that a re-entering angle is