EASTERN SLOPE OF THE CORDILLERAS. 
99 
Blake in the San Gorgono pass. About four miles below the summit, on each side of the pass, 
are high hills, with sharp outlines and ragged crests of crystalline felspar, intersected by 
quartz veins of a brownish red color, and hardly deserving the name of granite. These oc¬ 
curring on both sides of the pass must also cross it and produce a second axis eastward of the one 
lower down. To this axis may he attributed the dislocation and tilting of the pink strata, and 
in this axis the crystalline limestone may belong. 
In ascending the last five miles of the pass, and especially the last three, thick beds of con¬ 
glomerate and sandstone appear, which form the bluffs referred to. Sections afforded by the 
creek often exhibit 100 feet of thickness, and as all the beds were not exposed at one place, I 
think 300 feet to he the approximate thickness of these conglomerates in this place. From the 
lines of deposition they appear to be horizontal; hut viewing the slope to the Great Basin 
as merely the upper surface of these strata, the true dip may be about 6° northeast. They are 
yellow colored and very friable, being in some beds wholly unconsolidated. They contain 
angular felspathic crystals and paste similar to the pink beds alluded to, with the addition of 
gneiss, mica slate, and quartz pebbles, both rounded and square fragments of all being freely 
mingled in the mass. This addition serves in part to distinguish these conglomerate beds from 
the pink sandstones. They are still further recognized by their want of consolidation, and by 
their unconformability to the strata on which they rest. The pink sandstones repose on the 
axis, have been upraised and contorted by the elevating force, while, on the contrary, the upper 
conglomerates are almost horizontal, and are undisturbed by any cause. Derived in a great 
degree from the same sources, (primary granitoid rocks,) they mark successive periods of 
deposition. 
The descent from the summit of the Cajon pass to the Mojave river, where the trail strikes it, 
is over the hack of the pink sandstones referred to in the description of the pass, and capped by 
the conglomerates. The slope of the surface of the strata towards the river is 20°, a slope 
greater than that of the beds themselves, inasmuch as the inferior fourth of the slope is very 
much worn into ravines and canons by the water draining from off so large a level surface 
higher up. The true dip of the strata is northeast. The soil on this slope is a mixture of 
quartz and felspar, granitic detritus in fine powder, with pebbles of quartz, gneiss, and mica 
slate, derived from the degradation of the conglomerates. 
The tree yucca, of every possible form and size, was the predominant vegetation. Cedar 
trees of small size in the valleys near the summit, immediately below the pass. Dwarf pine, 
chemisal, and artemisia were the other shrub growths. The herbaceous vegetation was similar 
to that of the San Gabriel and Los Angeles valley ; hut the individuals on a dwarf scale. The 
whole vegetable growth is that of a desert region, and contrasts wonderfully with the luxuriance 
on the west side of the mountain range, the difference being due to the deficient supply of water 
on the east side of the Cordilleras. 
The rains falling upon the eastern summits of the sandstone strata and the melting of the 
winter snows form a body of water which sinks between the laminae and finds a subterranean 
course toward the valley of the Mojave, where, by their oozing out from the worn edges of the 
strata, they form springs, and go to swell the volume of the river itself. 
The Mojave river, where first struck, has a course north by west—lies several feet below the 
level of the sandstone in a small channel about thirty yards wide, worn in the strata; by cut¬ 
ting its way across the dip of the sandstones, and to some depth downwards, it has tapped some 
of the subterranean water courses alluded to. Along the whole course of the river it is very 
