46 EVOLUTION 



and the gradual shaping of the face of the earth to 

 something like its present configuration. Europe rose 

 definitively from the waves (stretching out far beyond 

 the present west coast of Ireland); Central America 

 emerged, and linked the northern and southern 

 continents; and the last fragments of the earlier con- 

 tinents that had united North America with Europe, and 

 South America with Africa and Asia, sank beneath the 

 ocean (or only lingered a little after the Tertiary epoch). 

 The climate was on the whole genial, though the alterna- 

 tion of seasons now definitely set in. The penetration 

 of a southern sea into the Mediterranean basin raised 

 the temperature of the south of Europe. Palms 

 flourished up to the north of France, and the lower 

 portion of what is now Great Britain had a sub-tropical 

 aspect. It is calculated that during the Oligocene and 

 Miocene the average temperature of Southern Europe 

 was from 10 to 12 degrees higher than it is to-day, while 

 Greenland had a temperature 30 degrees higher than its 

 actual one. 



As the Tertiary epoch drew to a close the temperature 

 fell once more, and again we find this phenomenon 

 connected with a great rise of mountains. I have 

 observed that it Is well to keep a broad view of these 

 climatic changes, and leave room for the action of 

 various causes. Many writers point out that the great 

 volcanic activity that had ensued on the formation of 

 the Apennines and Pyrenees at the beginning of the 

 Tertiary would pour volumes of carbon dioxide into the 

 atmosphere, and so cause a rise of temperature. As the 

 carbon was absorbed, the temperature would gradually 

 sink once more. Others point out that the constant 

 emergence and immergence of land would alter the ocean 

 currents; and a reserve must still be made in regard to 

 the astronomical theory. The tendency now is, however, 



