349 



CHAP. XVIII. 



On Volcanoes and Earthquakes. 



THE history of Volcanoes forms one of the most 

 popular and the most interesting branches of Geo- 

 logy. If the splendour and the consequences of 

 their eruptions attract the ordinary spectator, the 

 Geologist finds, in their phenomena, difficulties which 

 it is his duty to explain, and analogies widely con- 

 nected with other departments of his pursuit. While 

 they are the great sources of the rocks that are formed 

 in our own times, they throw light on the history 

 of the imstratified substances : in the power by which 

 they elevate and derange the surface of the earth, 

 they afford a clue to the nature of the far greater 

 changes which it has formerly undergone : and, in 

 reflecting on their seats and causes, we are led to 

 form conjectures respecting the interior parts of the 

 globe. 



If, in history as in nature, we find the memorials 

 of countries destroyed, of mountains formed and de- 

 molished, of cities overwhelmed, of rivers that have 

 changed their courses, of lakes swallowed up, or 

 generated, so, in compensation of all this evil, the 

 land is raised above the level of the waters and new 

 islands emerge from the ocean. The most delightful 

 parts of Italy have suffered from volcanic fires ; the 

 history of the Subapennine hills even proves that 

 vast tracts of this country have been raised into ex- 

 istence by their power. And, however terrific may 

 be the phenomena of volcanoes, they are less inte- 

 resting than these records of antient eruptions ; which 

 connect the present appearances with others, of a far 



