134 
GEOLOGY 
California to its extremity at Cape St. Lucas. This line of elevation will be described as the 
Peninsula Sierra. 
In addition to the lines of elevation which have been enumerated, there are others of less 
extent in the Great Basin, and separating it from the Colorado river. Ranges are also found 
between the Peninsula Mountains and the Colorado; hut all of these are only the southern 
extremities or prolongations of ranges which reach their greatest development beyond the limits 
of the State. The principal mountains of the State may thus he described under five groups or 
divisions—the Sierra Nevada, Bernardino Sierra, Peninsula Sierra, Coast Mountains, and Great 
Basin Mountains. 
SIERRA NEVADA. 
The explorations of the northern portion of the Sierra Nevada have shown that it is formed 
of many and nearly parallel ranges, enclosing elevated table-lands and valleys, precisely as in 
the Great Basin. There is no one predominant ridge or range towering high above the rest, 
thus forming a single and well-defined summit-line ; hut the ranges become gradually merged 
into the elevated region of the Great Basin. Very little is yet known of the central portions of 
the Sierra, hut all the ohservati ins which have been made show that it is similarly formed. 
The results of the survey, from Walker’s Pass southward, confirm those made at the north— 
establishing the existence of a series of elevated valleys or basins between ridges of nearly 
equal elevation. 
The general direction of the ranges composing the Sierra, from the sources of the Sacramento 
southward to the headwaters of the forks of the American river, is north and south, or north a 
few degrees west. South of this point, or nearly east from San Francisco, there is a deflection 
of the chain to the east, so that its direction becomes northwest and southeast. Still further 
south, the line is more nearly meridional, and from latitude 36°, or at the sources of Posuncula 
river, near Walker’s Pass, the chain curves towards the southwest to its termination at theTejon 
near the parallel of 35°. This curvature towards the southwest is the only known instance of a 
northeast and southwest trend in any considerable part of the mountains of California. It is, 
however, probable that this direction is due in part to the overlapping of ridges which have 
nearly a meridional direction. 
The pass called the Canada de las Uvas may be regarded as the extreme southern limit of the 
Sierra, this being the line of division between it and the Coast Mountains and Bernardino 
Sierra. The whole length of the chain, measured from this point to its northern end near to the 
boundary, is about six hundred miles, reaching from latitude 42° to 35°. It is not yet possible 
to determine, even approximately, the average altitude of this chain, for but very few observa¬ 
tions on the height of the peaks have yet been made. The elevation of many of the passes has, 
however, been determined, and estimates made of the heights of the adjoining peaks; but these 
have generally been in the most depressed parts of the chain, where it was most accessible and 
easily traversed. According to Captain Beckwith, the plateau, or broad plains, on the flattened 
crest of the Sierra, near the Madelin Pass, have an elevation of about 5,000 feet, and a width 
of twenty miles; while the adjoining ridges on each side rise from 500 to 3,000 feet higher. 
The observations of Messrs. Day and Goddard, of California, who have explored routes for a 
wagon-road near the central portions of the Sierra Nevada, show that the average elevation of 
the passes is not less than 7,000 feet. 1 
1 Report of George H. Goddard, esq., in report of Surveyor General of California, 1856. 
