CHAPTER IV. 
SALINAS RIVER VALLEY. 
Extent and position of the valley.—Gradual slope.—Character of the river—Non-navigability.—Geological character of 
THE VALLEY.—ALLUVIAL PLAIN, WITH TERRACES OR FLATS.—NATURAL VEGETATION AND PRODUCTIVENESS OF.—WESTERLY WINDS IN 
THE SOUTH OF THE VALLEY.—EFFECT UPON THE CLIMATE.—The GAVILAN HILLS.—STRUCTURE AND DISPOSITION.—POINT PINOS 
range.—Intrusion of trap through the sandstone.—Metamorphic effects produced in.—Sandstones of the san antonio 
hills —Structure and fossils of.—Recapitulation and observations upon the geology. 
The valley of the Salinas river is a plain of great extent, being almost 100 miles long and 
in places nearly 20 miles wide, in general narrowing as it advances southeast, until in 
places it is not more than half a mile in breadth. Its northern portion lies in Monterey 
county, stretching, as it advances south, into San Luis Obispo county. Like the Santa Clara 
valley, it is also of a triangular shape, presenting its base N.N.W. toward Monterey hay, upon 
which if opens without any intervening ridge, the slope of the valley being so slight and its 
surface so much depressed at the level of the tide that much of the low land is swampy and 
overgrown with tule, rush, willows, and marsh vegetation, through which the river lazily winds 
its way, forming small lagoons, from not having force enough to sweep its waters into the hay. 
The lower 60 miles of its course is over the gradual slope of the plain, which does not exceed 
20 inches to the mile, so that its waters are easily arrested; further up, south of San Miguel 
mission, where the valley narrows and the river in places cuts through a granitic region, its 
fall becomes more rapid; owing to this slight momentum, sand bars are heaped up by the ocean 
at its debouche into the hay, which completely destroys its navigation. 
It is not possible to navigate this river far up, the depth, 40 miles from its mouth, being 
under three feet in its deepest part, where its width might he nearly 100 yards ; hut when it is 
considered that this is the only river in the southern section of the State which does not canon 
through mountain passes to reach the ocean, and which rolls through an extensive and fertile 
valley, no doubt, as the population fills in, some efforts will he made which will both free the 
bars from its mouth and narrow the area covered by the lagoons and marsh in the lower 15 
miles of the plain. 
The whole valley may he described as an ancient alluvium derived from the degradation of 
the granitic, serpentine, chloritic, and sandstone formations, which go to form the mountains 
on either side; above this alluvium, and intermingled with its upper layers, is the modern 
detritus and fluviatile additions. But how little has been accomplished by modern action in 
either denuding or covering up the ancient alluvium, is evinced by the smooth surface of the 
plain, running even up to the base of the hills, and by the remains of the terraces, both upon 
the valley surface and upon the edges of the hills a few yards above the present base. 
The lower 60 miles of this valley is not a plain of uniform level, hut a series of low, flat 
terraces which extend in a north and south direction, and require to he ascended when the valley 
is crossed from west to east. The lower terrace is a fine stiff clay, occupying the west side of 
