90 A. Gray—Forest Geography and Archeology. 
Equally, in the rapid decrease of rain-fall southward, in its 
corresponding restriction to one season, in the continuation of 
the Cascade Mountains as the Sierra Nevada, cutting off access 
of rain to the interior, in the unbroken stretch of coast ranges 
near the sea, and the consequent small and precarious rain-fall 
in the great interior valley of California, we see reasons why 
the Californian forest is mainly attenuated southward into 
two lines,—into two files of a narrow but lordly procession, 
advancing aimee ure along the coast ranges, and along 
western flank of the Sierra Nevada, leaving the long valley 
between seowitvaly bare of trees. 
By the limited and precarious rain-fall of ria ee we may 
account for the limitations of its forest. But how shall we 
account for the fact that this district of Pensemtigale little 
rain produces the largest trees in th ot only pro- 
e what it can 
ie indeed, does the rain-fall of the coast of Oregon, great 
as it is, aa account for the extraordinary development of its 
orest ; for the rain is nearly all in the winter, very little in 
ea Yet here is more timber to the acre than in any 
other part of North America, or perhaps in apo other part of 
the world. The trees are never so enormous irth as some 
of the Californian, but are of equal belated least on the 
average—three hun red feet being ae and they stand 
almost within arms’ length of each oth 
The explanation of all this may sancti be found in the great 
climatic differences between the Pacific and the Atlantic sides of 
the continent; and the explanation of these differences is foun 
in the difference in the winds and the great ocean currents. 
The winds are from the ocean to the land all the year round, 
from northwesterly in summer, southwesterly in winter. An 
the great Pacific Gulf-stream sweeps toward and along the 
coast, instead of bearing away from it, as on our Atlantic side. 
e winters are mild and short, and are to a great extent a 
season of growth, instead of suspension of growth as with us. 
So there is a far longer season available to tree-vegetation than 
with us, during all of which trees may either grow or accumu- 
and in this latitude, trees use the whole autumn in getting 
ready for a six-months winter, which is sracnielians lost time. 
