MOJAVE RIVER—WARM SPRING—SALT. 85 
and barley had been harvested, and I reached the cation 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 edi 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 
dusty and looked like dry ashes. It was composed chiefly of clay and sand. In some places 
there was a thick growth of ‘‘salt-grass’’ and efllorescenses 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 ; the 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 Lieu- 
tenant 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 Cajon. 
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 summit- 
level—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 shown by 
the profile of the pass and is considered at greater length in the chapter devoted to the descrip- 
tion 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 valley 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 
