LYELL. 343 



show Ramsay, who will be interested in hearing, 

 that in spite of some Brazilian genera of trees and 

 insects, and not a few palms, and some reptiles of 

 good size, and many other fossil genera found on 

 both sides of the Alps and supposed to imply a 

 subtropical climate, I am not afraid to appeal to 

 ice as the only known cause capable of stratifying 

 these great masses in the manner in which they 

 occur." 



The evidence of former changes in climate was 

 thus strongly impressed on Lyell's mind, and the 

 astonishing truth began to be strongly impressed 

 upon geologists by him, that not only has the area 

 of Europe witnessed ages of tropical heat, but also 

 ages of considerable winter's cold, and that there 

 has been more than one glacial period. 



Lyell visited Vesuvius and Etna in 1858, and how 

 carefully he noticed every detail of the mountain 

 structure, and how little he cared about " roughing 

 it " may be gleaned from extracts from his diary 

 sent to his wife : — 



"Etna, Casa Inglese, Sept. 21, 1858. — Got off 

 with two guides and two muleteers and four mules, 

 at half past seven, in bright sunshine, from Nicolosi, 

 and after a beautiful sunny ride of three hours 

 through wooded craters, protected from the heat by 

 my umbrella, was gradually enveloped in clouds. 

 I saw a lava stream where the oaks had been sur- 

 rounded by lava, which had taken the form both 

 of upright and prostrate trunks, surrounding them 

 with tuff, and the wood being burned up they are 



