NOME II. VESICULAR LAVA. 35Q 



enlarging the crater, and diminishing the height 

 of the mountain. This hill itself had been pro- 

 duced by a former eruption in 1444*. 



" In like manner, Borelli informs us that in 

 the conflagration of 1669, the summit of Etna, 

 which rose like a tower to a great height above 

 the part which is level, was swallowed up in the 

 deep gulff. 



" I have already said, that when I visited 

 Etna, its summit was divided into two points, or 

 little mountains, one of which rose a quarter of 

 a mile above the other. I should not be sur- 

 prised were I to hear that in some new and 

 fierce eruption, the highest of these had fallen 

 in, and the two craters became one of much 

 larger dimensions. We know that the summit 

 of Vesuvius has sometimes fallen down in the 

 same manner; nor does it appear difficult to 

 assign the cause. It seems to admit of no doubt 

 that the highest parts of Etna, and other moun- 

 tains which vomit fire from their summits, have 

 their foundations on the sides of the crater, 

 which extend to an immense depth. In any 

 violent earthquake therefore, or impetuous shock 

 of the lava endeavouring to force a passage, it 

 may easily be imagined that those foundations 



* Ubi sup. Borelli Hist. Inc. Minx, 1669, 4to. 

 t Ubi sup. 



