526 



CENOZOIC TIME. 



when the period ended, the continents had their mountains raised in 

 general to their full height. 



4. Climate. — The climate of the United States, even the Northern, 

 during the Early Tertiary, was at least warm-temperate, as indicated 

 by the fossil plants. 



There is evidence, as Dr. Gray has remarked, 1 from the distribution 

 of Tertiary plants in the Arctic, made known by Heer and others, and 

 their relation to similar kinds in the Eastern United States and in 

 Asia, that the northern parts of the Continents of America, Asia, and 

 Europe were, during that age, under a nearly common forest vegeta- 

 tion, with a comparatively moderate climate. The genus Sequoia, of 

 California, has its species (as Heer has shown) in the Miocene of 

 Greenland, Arctic America, Iceland, Spitzbergen, Northern Europe ; 

 and one Greenland species is very near the great Californian S. gtgan- 

 tea ; and these were successors to Arctic Cretaceous species. There 

 were two species of Libocedrus in the Spitzbergen Miocene (Heer) ; 

 and one (L. decurrens Heer) now lives with the Redwoods of Califor- 

 nia, while the other occurs in the Andes of Chili. Gray adds that 

 the common Taxodium, or Cypress, of the Southern States, occurs fos- 

 sil in the Miocene of Spitzbergen, Greenland, and Alaska, as well as 

 Europe, and also, according to Lesquereux, in the Rocky Mountain 

 Miocene. These are only a few of the facts. From the Miocene 

 plants of Greenland (p. 514), Heer concludes that the mean annual 

 temperature of the Arctic regions, in the Middle Tertiary, was as high 

 as 48° F. 



Europe evidently passed through a series of changes in its climate, 

 from tropical to temperate. According to Yon Ettingshausen, the 

 Eocene flora of the Tyrol indicates a temperature between 74° and 

 81° F. ; and the species are largely Australian in character. The 

 numerous palms in England, at the same period, indicate a climate but 

 little cooler. 



The Miocene flora of the vicinity of Vienna, the same author pro- 

 nounces to be subtropical, or to correspond to a temperature between 

 68° and 79° F. : it most resembles that of subtropical America. Far- 

 ther north in Europe, the flora indicates the warm-temperate climate 

 characterizing the North American Tertiary ; and it is also promi- 

 nently North American in its types. In the Pliocene, the climate 

 was cooler still, and approximated to that of the existing world. 



The North American feature of the Miocene forests of Europe was 



probably owing to migration from America through the Arctic regions, 



and not from Europe; for a number of the European species, as shown 



by Lesquereux (p. 498), existed already in the American Eocene. The 



1 Mem. Am. Acad., vi. 1859, and Am. Jour. Sci., III. iv. 292. 



