NOME VII. VOLCANIC INTR1TE. 483 



linual, and accompanied by a hollow noise, 

 similar to that occasioned by a river falling into 

 a subterranean cavern. The lava at the time of 

 its being disgorged, from the impetuous and un- 

 interrupted manner in which it was ejected, 

 by striking against the walls of the vent, occa- 

 sioned a continual oscillation of the mountain. 

 Towards the middle of the night this vibratory 

 motion ceased, and was succeeded by distinct 

 and repeated shocks. The fluid mass, diminished 

 in quantity, now pressed less violently against 

 the walls of the aperture, and no longer issued 

 in a continual and gushing stream, but only at 

 intervals, when the interior fermentation elevated 

 the boiling matter above the mouth. About 

 four in the morning the shocks began to be less 

 numerous, and the intervals between them ren- 

 dered their force and duration more perceptible. 

 One might compare them to the thunder heard 

 in Italy during storms in summer, the loudest 

 claps of which are succeeded by rumbling sounds 

 which gradually die away. 



" While I was making my observations on 

 this grand eruption at the foot of Vesuvius, its 

 summit was tranquil, and no phenomena were 

 visible about its crater. I passed the night at 

 sea, between Calastro and La Torre, to have a 

 nearer view of this great operation of nature, 



