ON VOLCANOES AND EARTHQUAKES. 351 



volcanoes : but it is difficult, for want of explanatory 

 facts, even to approximate to the period of their ex- 

 istence or extinction, far less to determine their ab- 

 solute or relative ages. This difficulty is materially 

 increased by the difficulty of distinguishing between 

 the traps and the volcanic products, where the traces 

 of volcanic action have disappeared. Where these 

 eruptions have been submarine, the difficulty is in- 

 superable ; as both classes of rock are then under the 

 same circumstances, and are, in truth, identical. 

 These are the difficulties which yet beset the long 

 agitated question of the Euganean hills and the Vi- 

 varais ; and which will be found to exist in many 

 other cases. With respect to Italy, it is certain that 

 many of the volcanic appearances are prior to that 

 remote period when Europe was inhabited by races 

 of animals long since extinct in this continent. In 

 other cases, history offers some aid ; recording the 

 activity of many which have been long dormant. The 

 Scriptural record of the destruction of the cities on 

 the Dead Sea, is the last information which we possess 

 of the former activity of that volcanic district. 



The extinct volcanoes of Auvergne are among those 

 which have most excited the attention of Geologists, 

 from the peculiarity of their positions and appear- 

 ances. In Italy, the traces of this nature are innu- 

 merable ; sixty extinct craters being reckoned by 

 Breislak between Naples and Cumse. Many other 

 parts of this country, and of Sicily, present the same 

 records; which occur also in the Lipari isles, in Elba, 

 Sardinia, Ischia, Procida ; as well as in Lemnos and 

 other parts of the Greek Archipelago. St. Helena, 

 the Azores, the Cape de Verde islands, and Madeira, 

 present similar appearances, as do Java and other 

 islands of the eastern seas. Iceland is one entire 



