92 A. Gray—Forest Geography and Archeology. 
forests,—at least when not cut off from sea-winds by interposed 
chains of equal altitude. Trees such mountains will have. The 
only and the real wonder is, that the Sierra Nevada should rear 
such immense trees ! 
Moreover, we shall see, that this forest is rich and superb 
are to be compar 
In order to come ‘to this comparison, I'must refrain from all 
Mexican plateau type; that they are common to the mountain- 
all through that arid or desert region of Utah and Nevada, 
of which the larger part belongs to the great basin between the 
ocky Mountains and the Sierra Nevada: that most of the 
ountain trees are identical in species with those of the 
Pacific forest, except far north, where a few of our eastern ones 
are interm rmingled. I may add that the Rocky Mountains proper 
get from twelve to twenty inches = rain in the year, mostly in 
winter snow, some in summer show 
But the interior mountains get little, and the plains or val- 
leys between them less; the Sierra arresting nearly all the 
moisture coming from the Pacific, the Rocky Mountains all 
coming from the Atlantic side. 
ours is not i to th degree that the correspon regions 
west of the Rocky Mountains are. The ali from the 
Pacific which those would otherwise share, is—as ave 
= e 
seen—arrested on or near the western border, by the coast- 
ranges and again by the Sierra Nevada; and so the interior 
(except for the mountains), is all but desert. 
n the eastern side of the continent, the moisture supplied 
by the Atlantic and the Gulf of Mexico meets no such obstruc- 
tion. So the diminution of rain-fall is gradual instead of 
abrupt. But this moisture is spread over a east surface, and it 
is naturally bestowed, first and most on the seaboard district, 
i 
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