296 J. D. Dana on the Origin of Prairies. 
except on the high mountains; and at a point on the Columbia 3 
river, about 250 miles from its mouth, there is the “last tree” 
— a star system of facts was, later, observed. ‘The dry- 
of the climate, as is well known, increases southward; the 
arenes weal amount of rain along the coast of Oregon is 50 to 
60 inches; at San Francisco, California, according to Gibbons, but 
22 inches: and farther sout st, at the beginning of — 
the California pefiinsula, but 10 inches. So the forest region of — 
the sea-border narrows southward, failing on tbe lower ee 
moisture from the passing winds; — in the peninsula of Lower — 
California, the mountains even 
In the latitude of San Peantinees oy farther south, the Sierra 
Nevada is generally bare below a line three to four thousand — 
feet above the sea, except in the valleys; above this line there 
are nearly unbroken forests; and itis stated that 50 to 75 per 
cent more of rain falls ont thess mountains than on the Sacra: 
mento sa plains at their — foot. The eastern slope of 
oe ee orests, oe has been said, reach far down many of the 
valleys; for the stratification of the rocks leads often. to an 
reason a" ulte mMOISl, — 
ass of the — green, although over 
of = plain it was then (in Novem to 
