6 RESOURCES OF CALIFORNIA. 
formation. The point, however, as before stated, is by no 
means a fixed one: thus, during the night it extends farther 
downward than in daytime;.in cloudy weather, for the same 
reason, its course is more prolonged than under a clear sky. 
In the stream-beds themselves, however dry, water is gener- 
ally found a short distance below the surface. 
“The descent of these streams in the rainy season may be 
either a gradual process in the progressive saturation of their 
sandy beds, or, the saturation being accomplished by previous 
showers, the irruption may be sudden. A fine example of this 
sudden appearance was observed in the San Diego River, in 
December, 1849; when, after a rainy night, by which its sandy 
bed was completely saturated, the upper stream suddenly ap- 
peared in the form of a foaming body of water, moving onward 
at the rate of a fast walk, curling round the river-bends, ab- 
sorbing the pools, and soon filling its bed with a brimming, 
swift current. An instance of the more gradual descent was 
seen in the following season (December, 1850), when, from 
the absence of local rain, its downward progress was slow and 
interrupted.” 
The only navigable stream south of San Francisco Bay is 
the Salinas, and that but for small vessels, and near its mouth. 
North of San Francisco the main streams rising in the Coast 
Mountains are the Russian, Kel, Elk, Mad, and Smith Rivers, 
all permanent, but noge navigable. 
§ 5. Coast Lakes.—The only large lake in the Coast district 
is Clear Lake, which lies about eighty miles northward from 
San Francisco. It is twenty miles long, and varies in breadth 
from two to ten miles. Surrounded by a small valley of fer- 
tile land, it lies in a deep basin bounded by high mountains, 
with an outlet to the eastward, where its surplus waters are 
carried off by Cache Creek to the Sacramento. The water of 
Clear Lake is limpid; the vegetation on its banks abundant 
and vigorous; the scenery beautiftd and romantic. In Ama- 
dor valley, twenty-five miles eastward from San Francisco, 
there is a small lake, covering a couple of hundred acres. It 
