270 SIB CUAELES LYELL. 



million pounds. Some boulders from the Alps, 

 weighing three thousand tons each, are now found 

 on the Juras. " It must, I think," said Lyell, " be 

 conceded that the period required for the coming- 

 on of the greatest cold, and for its duration when 

 most intense, and the oscillations to which it was 

 subject, as well as the retreat of the glaciers and 

 the ( great thaw/ or disappearance of snow, from 

 many mountain-chains where the snow was once 

 perpetual, required not tens, but hundreds, of 

 thousands of years." 



In Arctic Siberia herds of elephants must have 

 roamed, as their bodies, covered with hair and flesh, 

 have been dug up in recent years. Great Britain 

 and Europe have been much warmer than now. 

 Our own immense coal fields show a former tropical 

 climate, with their great tree-ferns and tree-rushes, 

 while the remains of reindeers have been found in 

 Connecticut. 



No wonder Lyell became fascinated with the 

 history of the changes of this planet, and the life 

 of man before historic times. A great book seemed 

 open to him, and he studied it by night and by 

 day : the Archaean Time no life ; Paleozoic Time, 

 including the Silurian Age, with its shells and 

 trilobites ; the Devonian, with its fishes ; Carbonif- 

 erous, with its coal plants ; Mesozoic Time, includ- 

 ing the Reptilian Age with its reptiles ; Cenozoic 

 Time, including the Mammalian or Tertiary, with 

 its mammals, and Quaternary, or age of man. 

 Paleozoic means " ancient life ; " Mesozoic, "middle 

 life.;" Cenozoic, "recent life." 



