108 volcanoes; earthquakes. 



heat, its solid crust must formerly have been 

 everywhere thinner than it is now, we may con- 

 clude that volcanic actions and shocks must have 

 been far more extensive and frequent in ancient 

 ages than at present; and, in fact, we find in 

 every country the clearest proofs of volcanic power 

 having been once at work. It has been generally 

 proved by the researches of geologists that the 

 masses of trachyte and basalt, which are so widely 

 spread over the earth, and so nearly related in all 

 their chemical features to volcanic lava, are, 

 wherever they occur, volcanic products. These 

 rocks have in some places flowed forth just like 

 lava, in others have been heaved up in cones; 

 they have broken through masses of other strata, 

 and have often been forced, while yet liquid, into 

 all their clefts and crevices. 



We may indeed, with a probability which almost 

 amounts to certainty, consider all the great moun- 

 tain-chains of our earth as volcanic upheavals. 

 Not only do the numerous remains of sea-animals, 

 which we often find on the highest crests of moun- 

 tains, and of which almost whole strata are made 

 up, lead to this conclusion, but the whole formation 

 and condition of the rocks themselves give unan- 

 swerable witness to the fact. Besides, there are 

 plenty of instances of mighty upheavals of land 

 within historical times, and even in modern days. 

 Between the islands of Santorin and Therasia, 



