198 
GEOLOGY. 
Tejon, and the plain of the Tulares, are represented as far as Kern Lake ; and on the eastern, 
the elevated plateau of the Great Basin to the "Dry Lake. 
The chapter is also accompanied hy geological sections of the Sierra Nevada at the Tejon 
Pass, and at the Canada de las Uvas ; also, a partial section from the Tejon to Tah-ee-chay-pah 
Prairie. The profile lines of these sections are taken from the results of the Survey, the altitudes 
having been determined hy the barometer and level and the distances measured hy the chain. 
The observations upon the rocks were connected as far as possible with the different barojne- 
trical stations. As the line of survey, however, followed the lowest parts of the pass and for 
a part of the distance along the bed of the brook, the examinations of the rocks were necessa¬ 
rily at a little distance from the line. Th^ surveyed line was not in all cases transverse to the 
trend of the rocks, consequently it was not possible to represent them in their relative positions 
on the profile of the Survey ; it being prepared from the observations along the crooked trail, 
and consequently representing a much greater width of rock formations than exists. The 
profile for the geological section has, therefore, been modified, and the principal points of 
observation have been referred to straight lines drawn, as nearly as possible, transverse to the 
predominant trends of the rocks. The line of section on the eastern side of the summit is 
nearly transverse to the trends, but on the western side, along Tejon Creek, it is slightly oblique; 
thus the rocks on that side are represented with a greater thickness or development than they 
really have. 
In consequence, also, of this modification in the direction or length of the profile, the distances 
of the principal stations relatively to the Depot Camp do not correspond with those given on 
the railroad profile of the Survey. A scale of miles is placed on the section and will serve to 
give the distances with approximate correctness, hut it cannot be used with accurate results in 
measuring the thickness of the beds of rocks differing in character, for in some cases, as has 
been stated, the trends are oblique to the line of the section, and in others it was impossible to 
draw the line of demarcation between one modification of the gneissose metamorphic rocks and 
another. 
The section commences at the lowest point of the Tulare Valley, at Posuncula Lake, and 
extends westwardly in a straight line to the Depot Camp, at the Tejon ; thence across the plain 
to the entrance of the Pass, and through it to the Great Basin and the bed of the Dry Lake— 
the lowest point in that vicinity. The regular descent and unbroken surface of the Tulare 
slope cannot fail to he noticed ; and the difference of the altitude of its intersection with the 
granitic ridges of the Sierra, compared with the altitude of a similar point in the Great Basin 
on the other side, is well shown on the section. At station 11, the elevation of the upper edge 
of the slope is about 1,900 feet above tide; and on the Great Basin side, at station 212, the 
elevation of the slope is 3,100 feet. This shows a difference of 1,800 feet; hut the difference 
becomes greater if, instead of taking the elevation of the Tulare slope at station 11, it is taken 
at the base of the outlying ridge of granite west of the Depot Camp. 
The highest point of the section represents the lowest part of the divide, or ridge, of the 
Sierra that could be found in that vicinity. This is 5,300 feet above tide ; but on either side 
the ridges rise from one to two thousand feet higher. An elevated point on the north was 
estimated to be about 1,000 feet high. 
In each of the sections illustrating the chapter, the rocks or formations are represented as 
they appeared above the trail or surface. As in most cases the dip was nearly vertical, this 
representation is extended for a short distance above the line of observation, so that the char- 
