1903] FLORA OF SOUTHERN CALIFORNIA 207 
situated on the eastern border of the desert, and extending some 
75 miles (120*") ina NNE and SSW course, culminating at the 
south in Mt. Edgar, 6,350 (1,935™). 
DRAINAGE SYSTEMS. 
A country such as I have described, if in a region of abundant 
rainfall, would abound in limpid lakes, and in living streams, 
some of which would be of considerable volume. But far other 
is the case under the arid conditions which here exist. Even 
the streams rising in the high mountains of the San Bernardino 
range are infrequent, slender and inconstant; and of still less 
importance are those which drain the mountains to the south. 
In seasons of unusual precipitation they become raging torrents, 
and at such times the larger streams may carry their waters to 
the sea; but ordinarily their volume is insufficient to reach their 
nominal mouths, while in summer they dwindle down to thin 
rivulets which repeatedly sink and reappear in their wide sandy 
eds. 
The San Gabriel Mountains give rise on their desert slopes to 
Rock Creek,’ which ventures beyond their base only in wet 
weather. On their seaward side they are drained on the west 
by the Los Angeles and San Gabriel Rivers, and on the east by 
Lytle Creek, a tributary of the Santa Ana. 
The San Bernardino Mountains furnish the waters of the 
most important streams of the whole region. On the northern 
watershed the Mojave River has its source in Holcomb Valley, 
at an altitude of 7,000* (2,134™). It flows 75 miles (120*™) 
ina northerly direction, and then turning to the east continues 
for 60 miles-(96*™) further, the distances being measured in an 
air line, but following its meanderings its length is fully 200 
miles (320). In its course it disappears eight times in its sandy 
channel, leaving it entirely dry for long intervals, and is finally 
lost in Soda Lake (alt. 1,116, 340**), a flat, elliptical depres- 
Sion some 70 square miles (112 °¢*™) in area, occasionally flooded 
a few inches deep with water, but usually whitened with alkaline 
efflorescences. The eastern drainage of these mountains forms 
® This is the *Johnson’s River,” of Blake, Pac. R. R. Rep. 5:30 e¢ seq. 
