DISTRICT OF VESUVIUS. 93 



the elastic forces generated within their volcanic 

 region. The liquid masses (lavas), set in motion 

 by these forces, are urged in greatest quantities 

 towards the volcanic cone, as the point of least 

 resistance, and then flow out of the crater, unless, 

 as is very often the case — especially with lofty 

 volcanoes, — they first burst an outlet for themselves 

 at the foot of the mountain. 



All that has been observed of Vesuvius con- 

 firms the view, that, with the Phlegrean Fields 

 of Puzzuoli and with the neighbouring islands, 

 it forms a single volcanic district, of which the 

 mountain itself is the centre, and that any out- 

 burst, at any spot within this circle, tends to 

 prevent another from happening at any other part 

 of it. While a stream of lava was running from 

 the mountain Epomeo, on the isle of Ischia; 

 again, when the Monte Nuovo started up in the 

 Lucrine Lake, in 1538; and during the time 

 when volcanic action was going on in the Phle- 

 grean Fields; Vesuvius remained at rest, and 

 was covered with forests, and inhabited. Since 

 Vesuvius has been constantly at work, the islands 

 and the crater near Puzzuoli seem to have been 

 perfectly quiet. 



A great number of volcanoes often he in a line 

 one after another, on a long cleft rent through the 

 crust of the earth ; and they are often grouped in 

 double rows or chains, which bound valleys of 



