BERNARDINO PASS—ROCKS CUT BY DRIVING SAND. 
91 
this side of the mountain, as upon the other, the temperature of the stream was observed, and 
found to he 57° ; air, 60°. This was at sunrise. 
San Gorgono Mountain. —We began the descent of the eastern slope towards the Colorado, and 
I left the train and crossed over to the south side of the pass to examine the rocks of San Gor¬ 
gono mountain. The height of this mountain was estimated to be between six and seven 
thousand feet. It rises abruptly from the pass to a sharp-pointed summit; its base is deeply 
cut by numerous re-entering angles, and long, narrow ridges extend from it in various direc¬ 
tions. These radiating ridges have singularly rugged and serrated outlines, and showed out in 
bold relief, with sharp edges and angles; and there is but little verdure to hide them from 
view. The rocks are granitic and metamorphic, and have peculiar characters, differing from 
the granitic rocks of the Sierra Nevada and the Bernardino Sierra, but they simulate those 
developed in the ridges of the Great Basin along the Mojave river. The most important pecu¬ 
liarity of the rock consists in its highly laminated condition, and the frequent intercalation of 
thin layers or belts of white limestone, conformable with the planes of lamination. At a point 
about seven miles distant from Weaver’s rancho, and a little east of the divide, I ascertained 
the trend of the granite to be N. 5° to 10° W.; and several miles east, lower down the slope, 
in a projecting spur, the trend is still more to the west, being nearly N. 40° W. The layers 
are vertical. The following is the succession and composition of the rocks : 
a. 20 feet.—Feldspar and quartz in coarse crystalline masses, containing tourmalines. 
b. 40 to 50 feet.—Micaceous and gneissoidal, containing large garnets. 
c. 20 feet.—Granite, more compact. 
d. 20 feet.—White saccharoidal limestone, with parallel layers of a dark color. 
e. 15 feet.—Quartz rock. 
/. White, fine-giained granite. 
g. Gneissose. 
h. White crystalline limestone. 
i. Granite, or gneiss, (much mica.) 
This projecting spur is nearly northwest from the peak of the mountain, and is the first part 
of the mountain that extends far out into the pass. 
BocJcs cutjby driving sand. —A deep bank of drifted sand has accumulated on the east side of 
this point of rocks, it having been blown over by the wind. The wind which thus transports 
the sand is not an ordinary shifting breeze, but is a constant and powerful current of air 
sweeping through the pass from the west. It pours in from the Pacific in an apparently 
unbroken, unvarying stream, passing over the surface with such violence that all the fine grains 
of sand are lifted from the dry channels of the streams, and are driven along the descending 
slope until they find a final resting place to the leeward of the projecting spurs of San Gorgono. 
In respect to this prevailing current of air flowing inland from the Pacific, the pass appears to 
have the same relation to the interior valley of the Colorado that is held by the Golden Gate at 
San Francisco to the interior valley of the Sacramento and San Joaquin. They both appear to 
be great draught-channels from the ocean to the interior, through which the air flows with 
peculiar uniformity and persistence, thus supplying the partial vacuum caused by the ascent of 
heated air from the surface of the parched plains and deserts. 1 
I had before me remarkable and interesting proofs of the persistence and direction of this air- 
current, not only in the fact that the deep sand-drift was on the east side of the spur, but in 
the record which the grains of sand engrave on the rocks in their transit from one side to the 
1 It is very desirable that meteorological observations should be made at this pass. There are, doubtless, strongly 
marked periodical variations in the direction and force of this great air-current. 
