61 
GEOLOGY. 
now better known as the Mormon road, leading from the Great Salt Lake to San Bernardino 
and Los Angeles. No outcrops of rock wire found between Johnson’s river and this point. 
The earth was gravelly, and composed in great part of the debris of granitic rocks. The road 
was followed over similar soil down to the foot of the slope at the Mojave river, nearly twenty 
miles from the rrountains at the Cajon Pass. 
Mojave river, August 20.—The Mojave river at our camp was a shallow stream flowing in a 
bed of sand, no rocks nor even large gravel being visible. A considerable quantity of black 
sand was noticed on the dry, rippled surface of the bank, and several pans of the coarsest sand 
were washed out without finding any gold. I crossed the river to the right bank, and found 
outcrops of granite and metamorphic rock, and the left bank, a little below the depot camp, 
appeared to consist of horizontal strata of clay and sand, probably Tertiary. 
The granitic or metamorphic rocks rise abruptly from the river, as represented in the annexed 
section, the tertiary or sedimentary rocks forming a low bluff on the opposite side. 
SECTION AT THE CAMP, MOJAVE RIVER. 
Slaty or metamorphic granite traversed by veins .—The outcrop nearest the river had a distinct 
stratified appearance, and at a short distance looked like vertical strata of roofing slates. The 
color was black and glistening ; a fracture of the rock, however, developed a light-colored 
interior, and showed it to be a fine-grained syenitic granite. It was found to contain small 
crystals of light-colored mica and small garnets. It is hard and compact, and the mass has a 
rhombic cleavage. It owes its slaty appearance to its highly developed structural character, 
and much resembles a belt of highly laminated, but compact and crystalline, rock observed in 
the Tejon Pass. These outcrops have a distinct trend of north 5° east, dip 85° west; another 
observation gave north 8° east, dip vertical. 
Beyond this slaty or metamorphosed rock is a granular, gray granite, passing into syenitic 
granite. This rock forms the great mass of the ridge, and I did not detect any linear arrange¬ 
ment of the minerals. It is traversed by great numbers of feldspathic veins, which show a 
general parallelism, extending in the same direction as the slaty ridges, and dipping both east 
and west. 
A large part of this ridge is covered by huge blocks and masses of granite, that lie piled one 
upon another in utter confusion, and are completely impassable. There are no trees or shrubs 
of any great size. It will be observed from the figure that the slope of the Basin extends high 
up on the east side of the granite ridge, while it has been completely cut away by the river on 
the west. 
The vegetation along the bottom land of the Mojave is chiefly cottonwood and willows. 
The grass is, however, good and abundant, and there are probably many places along the 
stream where the alluvial lands could be successfully cultivated. The presence of large quan¬ 
tities of sand on the low lands near our camp indicated that the river frequently rose to a 
considerable height, so as to overflow a large surface, and render it unfit for cultivation. 
