GREAT PLAINS OF CALIFORNIA—RIVERS. 143 
and it is sufficient for the purposes of this chapter to give, in addition, a general description of 
the two principal valleys of the State—that between the Sierra Nevada and the Coast Mount- 
ains, and the valley of the Colorado Desert—with their relations to the elevated region of the 
Great Basin, and the broad coast slope south of the Bernardino Sierra. 
The great valley or plain of California, lying between the Sierra Nevada and the Coast 
Mountains, is traversed in its lowest portions by the Sacramento and San Joaquin rivers, which, 
flowing from the north and the south, unite in the latitude of San Francisco, and empty into 
the bay. It, however, extends far southward of the sources of the San Joaquin, and includes 
the broad valley of the Tulare lakes, generally known as the Tulare Valley, which, although at 
some seasons without drainage to the sea, is, topographically, a part of the extended plains 
under consideration. The limits of the valley on the south are determined by the union of the 
Sierra Nevada and the Coast Mountains under the parallel of 35°, and on the north it extends 
beyond the parallel of 40?, near to the head waters of the Sacramento, or over five degrees of 
latitude, a distance of more than 350 miles. Its average breadth south of the mouth of the 
American river, in the Sacramento, is about fifty-five miles; it being fifty miles at the mouth 
of the Sacramento and San Joaquin, at the sources of the San Joaquin sixty miles, and across 
the Tulare lakes over sixty. its whole area probably exceeds 15,000 square miles, which is greater 
than the united areas of the States of Massachusetts, Rhode Island, and Connecticut, 
This broad area is unbroken by hills or sudden swells of the surface, and thus, being nearly 
level, becomes a vast plain—the vision in the direction of its length being bounded by the dis- 
tant horizon alone. The broad and level expanse is made more evident and striking to the 
observer by the general absence of trees, and the arid and و یت‎ surface during the dry 
season. ۰ 
The average elevation of these plains above the sea is not great. A large portion of the 
surface bordering the Sacramento and San Joaquin, near their mouths, is but little elevated 
above tide-water, and is overflowed during freshets. This portion is, however, properly the 
delta of those streams, and is an extended alluvial marsh, where rushes and grass grow luxuri- 
antly. A low border of alluvium is also found along the principal rivers. From this level the 
surface rises gently and.very uniformly towards the base of the mountains, reaching, in some 
places, an elevation of only two or three hundred feet at the foot-hills, or first sudden swells of 
the surface, at the base of the more rocky and higher ridges of the mountains. At other points 
towards the south end of the valley and, probably, also at the northern end, the upper part of 
the slope has a much greater altitude, and extends far up on the sides of the mountains. Thus, 
at the Tejon the lowest portion of the Tulare Valley at Kern Lake is 398 feet above tide, and the 
surface rises from this polnt very gradually towards the surrounding mountains, reaching, in a 
distance of about nineteen miles , an elevation of 1,900 feet at the entrance of the Tejon Pass, 
and 1,600 at the entrance of the Cañada de las Uvas. 
The two great streams, the Sacramento and San Joaquin, follow the axis of the valley for the 
greater part of their course, and receive the waters of numerous tributaries, flowing nearly at 
right angles to them, and rising in the Sierra Nevada on the east. On the other side there 
are, however, but few streams from the Coast Mountains, and these are of slight extent or im- 
portance. Most of the rivers from the Sierra are liable to great floods or freshets, and thus vary 
in the volume of their water at different seasons. At the border of the great valley, where they 
emerge from the cafions of the mountains, their banks are high and steep, and generally ter- 
raced ; lower down the stream, the banks become lower, the streams wider, and, in many in- 
