58 
GEOLOGY. 
grass, and aquatic flowers. Our blankets were unrolled under the wide-spreading branches of 
an evergreen oak; its huge trunk, already half burned away by previous camp-fires, served as 
our fire-place, and the hollow part above made a perfect chimney. Here, after a day of toil and 
fatigue, we enjoyed a hearty supper on choice cuts from a fat buck, and on teal ducks from the 
lake, both provided by the rifle of our friend Ridley, who had accompanied us from the Tejon. 
Summit-level of the Pass to the San Francisquito Rancho .—No strata of sandstone or clay were 
seen in the neighborhood of our camp near the summit. The white granite appeared to predomi¬ 
nate, and in some places looked like exposures of chalk among the green bushes. The ridges 
had gently sloping sides, and, being covered by soil, very few opportunities for examining the 
rocks were presented. In descending the brook, however, the ravine of the pass becomes more 
narrow, and the stream, by its velocity, has cleared away the earth so that the underlying rock 
is brought to view. It here loses the peculiar whiteness characteristic of that at the summit, 
and is more gray, and assumes a structural character, the minerals being arranged in long par¬ 
allel lines or planes. In some places the rock is syenitic ; in others, mica predominates ; but, in 
general, feldspar is the predominant mineral. Considerable quantities of epidote were seen in 
seams and in coatings upon surfaces of cleavage or divisional planes in the rock. The laminated 
structure was highly developed in many places, the rock becoming gneissose. Feldspathic veins 
traversing the rock were also noted. It is very probable that the rocks of the lower parts of the 
ravine of the pass are metamorphic, while the higher or summit portions are eruptive. I have 
given the laminated or gneissose portions a distinct coloring on the section. The trend of the 
rock, nearly three*miles below camp, was N. 70° E; and at another place, N. 94° E. ; being 
conformable to the general direction of the main chain. This part of the pass is more rocky 
than the upper portion, and the granitic and metamorphic rocks rise directly from the brook, so 
that the trail is confined to its bed. 
Sandstone strata .—About six miles from the summit the whole character of the scenery of the 
pass changes; the hills are lower and more numerous, and present many abrupt and bold 
escarpments. They are of sandstone and conglomerate, probably Tertiary, and are similar in 
their appearance to those developed at the base of the Sierra, at the head of the Tulare valley. 
The outcrops of these sandstones are of great thickness, and they occupy a wide area on the 
southern flank of the mountains. They are probably the principal formations between the 
mountains and the Pacific. The planes of stratification are very much bent and folded, and are 
in many places raised so as to stand nearly on edge. Natural sections made by the brook are 
very numerous, and beautiful exposures of the edges of the strata, standing at almost all angles 
with the horizon, are seen on each side. The outcrops do not exceed three to five hundred feet 
in height above the trail, and it was not possible for me to make any satisfactory estimate of 
the thickness of the group of beds thus disturbed. 
In the rapid observations I was obliged to make I could not connect the numerous flexures 
which were indicated by reverse dips. The following trends and dips were observed at several 
distant points: 1 
N. 40° E., dip 70°. 
N. 30° E., dip 70°-80°. 
N. 10° E., dip 10°. 
N. 40° E., dip 70°. 
N. 25° E., dip 75° southeasterly. 
N. 25° E., dip 65° northwesterly. 
The two last observations were made on exposures one-eighth of a mile apart, and an anti¬ 
clinal axis was indicated. 
1 These results are not corrected for variation. 
