FOREST GEOGRAPHY AND ARCHZOLOGY. 227 
tain-tops under cover of the frigid climate due to elevation. 
The conditions of these on different continents or different 
mountains are similar, but not wholly alike. Some species 
proved better adapted to one, some to another, part of the 
world; where less adapted, or less adaptable, they have per- 
ished ; where better adapted, they continue, — with or with- 
out some change; and hence the diversification of alpine 
plants, as well as the general likeness through all the northern 
hemisphere. 
All this exactly applies to the temperate-zone vegetation, 
and to the trees that we are concerned with. The clew was 
seized when the fossil botany of the high arctic regions came 
to light; when it was demonstrated that in the times next 
preceding the Glacial period — in the latest Tertiary — from 
Spitzbergen and Iceland to Greenland and Kamtschatka, a 
climate like that we now enjoy prevailed, and forests like 
those of New England and Virginia, and of California, 
clothed the land. We infer the climate from the trees; and 
the trees give sure indications of the climate. 
I had divined and published the explanation long before I 
knew of the fossil plants. These, since made known, render 
the inference sure, and give us a clear idea of just what the 
climate was. At the time we speak of, Greenland, Spitzber- 
gen, and our arctic sea-shore had the climate of Pennsylvania 
and Virginia now. It would take too much time to enumer- 
ate the sorts of trees that have been identified by their leaves 
and fruits in the arctic later Tertiary deposits. 
I can only say, at large, that the same species have been 
found all round the world; that the richest and most exten- 
sive finds are in Greenland ; that they comprise most of the 
sorts which I have spoken of as American trees which once 
lived in Europe, — Magnolias, Sassafras, Hickories, Gum- 
trees, our identical Southern Cypress (for all we can see of 
difference), and especially Sequoias, not only the two which 
obviously answer to the two Big Trees now peculiar to Cali- 
fornia, but several others; that they equally comprise trees 
now peculiar to Japan and China, three kinds of Gingko- 
trees, for instance, one of them not evidently distinguishable 
