CHAPTER X 



THE LIFE OF YESTERDAY 



THE entire period comprised between the 

 Eocene and the present, known as the Cenozoic 

 era, or that of the new life, is variously esti- 

 mated at from 4,000,000 to 10,000,000 years, 

 the last figures being probably nearer the mark 

 than the first. It was marked, among other 

 things, by a gradual change in the climate of 

 the world, due to a general cooling off and 

 lowering of temperature, particularly at the 

 poles. At the commencement of Eocene time 

 sequoias and other temperate trees grew in 

 Greenland, and palms in Wyoming and south- 

 ern Europe, while by the close of the Pliocene 

 the elevation of the northern part of the globe 

 had brought about an arctic climate even more 

 severe than that now prevailing. 



As a natural consequence, the entire flora 



and fauna of the northern hemisphere was 



251 



