118 KAMBLES OF A NATURALIST. 



their action by these strata, which had been con- 

 tinually augmenting in number and solidity. Unable 

 to break through them, the internal forces upheaved 

 them, and this violent movement necessarily broke 

 them, by which a free communication was established 

 between the bowels of the earth and the atmosphere. 

 M. de Beaumont is of opinion that before this event 

 there must have been at this point a multitude of 

 ephemeral volcanoes, which, since that period, have 

 been replaced by a permanent volcano. 



But we know that in eruptions the ejected matter 

 is not confined solely to solids and liquids, for 

 the quantity of gaseous matter which escapes through 

 the craters very far exceeds the volume of the lava 

 and scoriae. It is, therefore, easy to comprehend 

 that the enormous vault formed by the upheaval of 

 Etna must soon have needed support. Dislocated, 

 moreover, by the very efforts which had given it 

 birth, it must in a great measure have fallen back into 

 the abysses which it had covered, and it is precisely 

 to such a catastrophe as this, that the Val del Bove 

 owes its origin. If this origin be once admitted, we 

 shall be readily able to understand the striking rela- 

 tionship which exists between the craters that sur- 

 round this valley, and the crater of the volcano itself. 

 These craters are evidently continuations of one 

 another, and collectively they form the circumference 

 of the ampulla which had been upheaved on the 

 surface of the soil. The vault, in falling in, exposed 

 a section of the strata of which the escarpments of 

 the valley were all equally composed, and which we 

 again meet with on the Piano del Lago in the inte- 



