FOREST GEOGRAPHY AND ARCHEOLOGY. 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 the}' equally comprise trees 

 now peculiar to Japan and China, three kinds of Gingko- 

 trees, for instance, one of them not evidently distinguishable 



