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 idiosyncrasy 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- 



