Extracts from a work by Dr. J. B. Trask, (U. S.) on the Geology of California.
SOILS OF THE VALLEY SANTA CLARA AND SHORES OF SAN FRANCISCO BAY.
The soils on the Bay San Francisco differ much on its eastern and western sides; both borders of the bay present the tertiary series, but both do not present the trapean rocks to the same degree of development; this, then, of course, will cause a distinctive and marked difference in the productive capabilities of either shore. It will be found in all the soils which have been derived in whole, or in part, from rocks more recent than the tertiary group, that a more extensive and varied adaptation to agricultural purposes will be present; this will be particularly manifest in those sections where the tertiaries, containing organic remains, enter somewhat largely into the components of the soil produced from such sources.
Under a proper course of treatment these lands will be made available for the purposes of the agriculturist, and our already large domain of arable lands thus much increased. The situation of these lands in the interior is such that they may be easily reclaimed should they ever fall within the jurisdiction of the State, which undoubtedly they will, under the law regulating “saline lands.� In the counties of San Francisco, Santa Clara, and Alameda, the wet land that may be made available by drainage is about seventy square miles, exclusive of the “saline lands� at the southern part of the county of Santa Clara.
Most of the valley sections of this range of country is arable land, and that which is not can easily be made so when required; the agents for bringing this about being found in the adjoining hills to the east. The character of the soil and climate adapts it to all the productions of temperate climates, and where local position modifies the climate of any section, it is found capable of producing plants of the tropical latitudes.
The extreme south-eastern part of this valley would be adapted to the growth of foreign fruits and other products, but it must be beyond the influence of the cold sea-wind that passes inland across the range of lower hills which divides the Salinas, Pajaro, and Santa Clara valleys, the effect of which would be to blight the fruit, though the plant or tree might continue to thrive.
The low hills that flank the east side of the valley contain all the elements required for the culture of tropical plants and fruits; the climate and soil will be found adapted, and the only agent that appears in the least to be wanting is water sufficient to supply the demands of those plants. From the appearance of small lagoons and rivulets at different elevations it is presumable that a sufficient quantity of this agent may be found a short distance below the surface.
As a general rule the mountains lying upon the east border of the valley Santa Clara are covered with a soil superior to that of the plains, and of much greater depth. I have measured the depths of these soils in many places, and where it is well developed have found it varying from four to eleven feet for miles continuous: its extreme fertility produces heavy crops of the native grains and grasses, which annually contribute to its increase by their decomposition.
Although these lands are situated within the reach of the sea breeze from the Bay of San Francisco, they are protected from its cold by the slope of the hills and the modifications of its temperature acquired in its passage down the bay before reaching the northern portion of the valley. So much is the temperature increased that an addition of ten degrees is often acquired in its transit from San Francisco to the head of the valley, a distance little rising fifty miles. This increase of temperature in the air is accompanied with an increase in its capacity for moisture, hence it is usual to find a slight aqueous haze, which results from the condensation of its moisture, hanging about this entire range of hills during the summer months, and is usually seen early in the morning.
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