a few hundred feet, severing the southern California islands from their shore connections and allowing the Pacific Ocean to fill a shore valley and form the bay of San Francisco and other bays along the coast. Out from the present Pacific beaches of California, there are sharp and deep cliffs in the ocean floor that are believed to be the old shore of the primeval sea when California was in the making.

Somewhere in geologic time, California assumed a form recognizable as the progenitor of the State as now seen. The Sierra Nevada and its north and south connections dominated its eastern borders and the ridges of the Coast Range looked down on the western ocean. Between the two, covering what is now called the "great valley of California" was an expanse of waters that later broke through the Coast Range and uncovered the foothills, the wide valley plains and enabled the great rivers to build up the lower central areas to reclaimable marshes which are now recognized as rich delta regions. While this was going on centrally in the State, glacial sculpturing, volcanic outpourings and meteorological agencies were developing topography in the mountain encirclement of the great valley which brought the State nearer and nearer to what we now recognize as outstanding local features of hill, mesa and valley areas supporting growth of plants and ministering suitably to the higher classes of animal life and later still to the uses of mankind.

While such changes were taking place and previously submarine activity perhaps had more to do

with the upbuilding of the California of today than surface agencies. It has been estimated that more than half the land surface is of sedimentary substances. These include sandstones, shales and clays of inorganic origin. The ancient waters of the State, however, not only received and held fast these scourings from the uplifts by stream, wind and glaciers but supported a submarine growth of coral and other lime-collecting organisms which gave limestones literally thousands of feet in depth in some places. The other chief component of the California surface is of igneous origin. Less than one-half is counted as being chiefly granitic (of which the Sierra Nevada Mountains are a great irregular block of granite), and lava flows productive of other rocks and of volcanic ash. This line of creation is still active in the recent out-pours of Mt. Lassen in northern California, although the adjacent higher cone of Mt. Shasta has not been active.

In the possession of animal and plant life in geologic time, the vestiges do not indicate that California was particularly rich as compared with other parts of the earth's surface, although in special interest of some of the forms, and in the unique manner in which the remains have been preserved, the paleontology of California is very notable from a scientific point of view.

Owing to the multiplicity of geologic agencies and the diversity of materials they produced and transported, not only within narrow geographical limits but by superposition, because of alternating eleva

tion and depression of the crust upon which they worked, the geological map of California is a complex which baffles popular exposition, even though the owner of a single farm may have between his own fences almost an epitome of it. The popular wonder and significance of the geology of the State are embodied in the soils which have been created for the development of California agriculture and of which a sketch will be undertaken in Chapter II.

TOPOGRAPHY AND CLIMATE

From the brief outline of its geological history, it can readily be inferred that the surface conformation of California would be strikingly diverse in both general and local features. Within the boundaries of California stands the highest mountain of the continental United States 1 (Mt. Whitney, 14,501 feet above sea level); the deepest valley (Death Valley, 278 feet below sea level); the greatest stretch of latitude of any state (9 degrees); the longest sea coast of any state (1200 miles). In addition, California has the only active volcano in the continental United States and it is still making new topography. These and many similar facts are suggestive of great topographical variety. Four transcontinental railway lines start at sea level on San Francisco Bay and run northerly, easterly and southerly, traversing distances of 100 to 300 miles without rising more than

1 The term "Continental United States" as used by the U. S. Census excludes Alaska and Mt. McKinley, which is higher than Mt. Whitney.

200 feet above sea level, while in the next 100 to 300 miles they must rise from 4,000 to 7,000 feet to reach the lowest crossing places in the mountain barriers. This is a good indication of central California's great stretches of low valleys and the height of the mountain ranges that encircle them.

Study of the relief map (Plate I) will impress these facts, viz: (1) that California is thickly set with high mountains closely connected into continuous ranges roughly parallel and having a general trend from northwest to southeast; (2) that associated with these mountain ranges are wide open spaces which are for the most part broad valleys of relatively low elevation, although some of the open spaces, chiefly on the east side of the central and northern regions of the State, are high plateaux; (3) that such a multitude of mountains suggests that there must be innumerable smaller valleys at various elevations; (4) that in nearly all parts of the State there are mountains in sight, towering above the small valleys and discernible even from the central parts of the largest valleys as features of the horizon lines; (5) that such variation in topography, generally within short distances, indicates great diversity in elevation, exposure, soil and other natural conditions which expresses itself in corresponding diversity in agricultural production and in the comforts and hardships of living.

Such observations might lead to a conclusion that California must be incongruous, narrowly antagonistic in its natural conditions and unfitted for great

surpluses of standard food commodities. Such a conclusion would be incorrect, for at least two reasons: first, California is so large that many subdivisions may still include considerable areas; second, owing to peculiar topography, and conditions largely dependent on it, corresponding conditions are multiplied through hundreds of miles of distance and ensure to hundreds of thousands of acres similar producing capacities, though they may be geographically far apart. This fact is demonstrated by the wide distribution of the numerous large products that are now creating the wealth of the State and is made intelligible by a review of environment and topography in their relation to local climatic conditions.

Concrete illustration of agencies determining the climate of California will be secured by reference to the requirements of the orange, which is not only a world token of salubrity but is (next to hay) the greatest single crop produced in California, the "farm value" in 1920 being fixed by the United States Bureau of Crop Estimates at $51,425,000.

Natural conditions befitting the growth of the orange exist in suitable situations in the interior valleys at the north, and in coast valleys at the south all the way from Shasta County to San Diego County. It is surprising that similar climate should be found. through a distance of between seven and eight degrees of latitude. If the north and south distance of over 500 miles that separates Shasta and San Diego counties be laid off in corresponding latitudes on the Atlantic Coast, Georgia would be at one end