210 ESSAYS. 
corresponding restriction to one season, in the continuation of 
the Cascade Mountains as the Sierra Nevada, cutting off ac- 
cess of rain to the interior, in the unbroken stretch of coast 
ranges near the sea, and the consequent small and precarious 
rainfall in the great interior valley of California, we see 
reasons why the Californian forest is mainly attenuated south- 
ward into two lines, — into two files of a narrow but lordly 
procession, advancing southward along the coast ranges, and 
along the western flank of the Sierra Nevada, leaving the 
long valley between comparatively bare of trees. 
By the limited and precarious rainfall of California we 
may account for the limitations of its forest. But how shall 
we account for the fact that this district of comparatively little 
rain produces the largest trees in the world — not only pro- 
duces, alone of all the world, those two peculiar Big Trees 
which excite our special wonder, — their extraordinary growth 
might be some idiosynerasy of a race,— but also produces 
Pines and Fir-trees whose brethren we know, and whose 
capabilities we can estimate, upon a scale only less gigantic? 
Evidently there is something here wonderfully favorable to 
the development of trees, especially of coniferous trees ; and 
it is not easy to determine what it can be. 
Nor, indeed, does the rainfall of the coast of Oregon, 
great as it is, fully account for the extraordinary development 
of its forest; for the rain is nearly all in winter, very little 
in summer. Yet here is more timber to the acre than in 
any other part of North America, or perhaps in any other 
part of the world. The trees are never so enormous in girth 
as some of the Californian, but are of equal height, at least 
on the average, three hundred feet being common, and they 
stand almost within arms’ length of each other. 
The explanation of all this may mainly be found in the 
great climatic differences between the Pacific and the Atlan- 
tic sides of the continent ; and the explanation of these differ- 
ences is found 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 win- 
