THEORY OF THE EARTH. 35 



have produced at the surface of the globe. After 

 a volcano has announced itself, by some shocks of 

 an earthquake, it forms for itself an opening. 

 Stones and ashes are thrown to a great distance, 

 and lava is vomited forth. The more fluid part of 

 the lava flows in long streams, while the less fluid 

 portion stops at the edges of the opening, raises its 

 margins all round, and forms a cone, terminated by 

 a crater. Thus volcanoes accumulate upon the sur- 

 face matters which were previously buried in the 

 bowels of the earth, after modifying their nature, 

 and raise themselves into mountains. By these 

 means, they have formerly covered some parts of 

 our continent, and have also suddenly produced 

 islands in the middle of the sea. But these moun- 

 tains and islands have always been composed of 

 lava, and all their materials have undergone the 

 action of fire : they are disposed as matters should 

 be, which have flowed from an elevated point. 

 Volcanoes, therefore, neither raise nor overturn 

 the strata through which their apertures pass ; 

 and if some causes acting from those depths have 

 contributed, in certain cases, to raise up large 

 mountains, they cannot have been volcanic agents 

 of the same nature as those which exist at the 

 present day. 



Thus, we repeat, it is in vain that we search, 

 among the powers which now act at the surface of 



c 2 



