UNCLE IN ENGLAND. 49 



changes produced in the interior by the different 

 causes which my uncle had already mentioned, 

 he said to us this morning, " Those alterations 

 are so gradual that years are required to detect 

 their operations, or to measure the rate of their 

 progress ; but the gigantic changes effected by 

 volcanoes and earthquakes carry their desola- 

 tion at once over whole districts. You have, no 

 doubt, read an account of some of the destruc- 

 tive eruptions of mount Vesuvius, by which you 

 know the city of Herculaneum was overflown 

 with a torrent of melted lava, and Pompeii was 

 buried, and remained concealed for many cen- 

 turies under the ashes that were ejected from 

 the crater. 



** Large tracts of country seem to have been 

 produced by volcanoes, and after the lapse of ages 

 the decomposed lava has become a fertile soil. 

 But even within the reach of history new vol- 

 canic mountains have been elevated, and new 

 islands have sprung out of the ocean. Pliny and 

 Seneca describe two marine volcanoes that 

 raised themselves out of the water in the Gre- 

 cian archipelago ; and in the beginning of the 

 last century the same thing again happened in 

 the same place. In 1720, a small volcanic 

 island rose out of the sea near Terceira, one of 

 the Azores ; and in 1811, among the same group 

 of islands, another violent eruption of lava pro- 

 duced an island of considerable altitude ; but in 



F 



