Force of Volcanic Fires. [Book VI. 



lava generally pafles, though fometimes it burfts 

 through the fides, and even proceeds occafionally 

 from the bottom of the mountain. Sometimes the 

 crater falls in and is effaced, fometimes, in extinguifhed 

 volcanoes, it is filled with water. Sub-marine vol- 

 canoes have been obferved, and from thefe fome 

 iflands have derived their origin. Volcanic fires, 

 taking place at the bottom of the ocean, would fre- 

 quently, by the expanfive force of the (teams which 

 are generated, elevate thofe parts which were once 

 at the bottom of the deep, and overflow thofe which 

 were habitable earth. It is very probably conjee- 

 tured, as was noticed in a preceding chapter, that fub- 

 terraneous convulfions operated more powerfully in 

 the early ages of the world than at any later period ; 

 and indeed fuch an hypothecs is fupported by the 

 moil: probable reafoningi fince we may well conceive, 

 that at the firft confolidation of the earth, much hete- 

 rogeneous matter would be included in the different 

 mafles, which might produce more frequent fermen- 

 tations than at any after periods, when thefe have 

 been, if I may fo exprefs it, purged off by frequent 

 eruptions, and in many parts, perhaps, rectified and 

 aflimilated by flow and fecret procelTes in the bowels 

 of the earth. But hiftory was not cultivated till a very 

 late period, and the moft eventful ages of nature have 

 patted unrecorded. 



The force of fubterraneous fires, or rather of the 

 fleam which is generated by them, is fo great, rhaC 

 confiderable rocks have been projected by Vefuvius 

 to the diftance of eight miles. A ftone was once 

 thrown from the crater of that volcano twelve miies, 

 and fell upon the Marquis of Lauro's houfe at Nola, 

 which it let on fire. One alfo, which meafured twelve . 

 feet in height and forty-five in circumference, was car- 

 ried 



