88 
GEOLOGY. 
but, as yet, there is no evidence of this, other than mineral composition and appearance. A 
further examination is highly desirable. 
Granite .—Outcrops of sandstone, similar to those described, are found along the trail for 
seven or eight miles below the summit. The valley then grows more narrow, and the stream 
canons in granite rocks, which rise in high mountains on each side. These granites are both 
compact and gneissose, and are associated with the talcose slates, traversed by quartz veins, 
similar to those occurring at the Pass of San Francisquito. Erupted trappean rock was observed 
in connexion with these formations. This part of the valley was passed in the night, and it 
was therefore impossible to make detailed observations on the varieties and peculiarities of the 
granitic rocks. 
In the upper part of he pass, nearest to the Great Basin, the dry bed of the stream, that 
flows in considerable volume in the rainy season, is strewed with houlders of white lime¬ 
stone, veined with blue; these indicate the existence of a parent mass in the vicinity. 
Slope of drift .—On approaching the valley of San Bernardino a hank of loose drift-soil and 
rocks is seen along the base of the mountain on the left. This is a remnant of the former slope 
that stretched from one side of the valley to the other, and was connected with those hounding 
the Santa Anna river on the west. It has gradually been moved by the excavating power of 
the stream, and the material has been carried down to form a new slope below, now a portion 
of the valley of San Bernardino. Abundance of good stone for purposes of construction can he 
obtained in the central portions of the pass. The principal timber along the road is plane tree 
and oak, hut pine can he procured from the high, sheltered canons. Near the summit, various 
interesting shrubs were seen ; the mancinita, with its brilliant red hark, being conspicuous. 
The wild plum was also abundant, and a species of aloe ( maguey ) was occasionally found. A 
beautiful oak with enormously large acorns, similar to those seen in the Tejon Pass, grows by 
the road side, and was loaded with fruit. 1 Many of the plants which seemed to be peculiar to 
the Great Basin were seen in this pass, and contrasted with the vegetation common to the 
Pacific slope. This distribution has probably resulted from the fact that there is no crest or 
elevated ridge to separate the Basin from the waters of the creek, and many of the shrubs or 
their seeds may have been floated down by the stream. 
This pass and the old Spanish trail is now principally used by the Mormons and other 
emigrants from the Salt Lake to Southern California. It was through this pass that great 
numbers of horses ar.d cattle were formerly driven out into the Great Basin by bands of Pai-Ute 
Indians, who entered the valley by night and were safely back again through the pass with 
their spoils before morning. It is said that another pass, nearly parallel with this, but much 
more rugged and steep, is found about three miles to the westward, and is called “El Cajon de 
los Negros.” 
1 Drawings of the leaves and fruit of this oak, and specimens of each, have been submitted to Dr. Torrey. He has determined 
it to be a new species, and named it Qwfcws crassipocula. 
