NOME VII. 



VOLCANIC JNTRITE. 



verse. It is therefore probable that these fumes 

 are the production of substances, in the neigh- 

 bourhood of the brim of the crater, in a state of 

 decomposition. 



" When the mouth of Vesuvius is observed 

 from any distance, and during the prevalence of 

 moisture in the atmosphere, a mass of vapour 

 seems to rise from it which mingles with the 

 clouds. Entirely distinct from any volcanic 

 cause, these are only the humid vapours in the air, 

 attracted by the conical shape of the mountain, 

 and imprisoned in the vast cavity of the caul- 

 dron. Vapours which spring from, or are dif- 

 fused over a plain, are dissipated by the air and 

 winds ; but when enclosed, they are much less 

 readily dispersed. 



" The western portion of Somma must be con- 

 sidered as connected with the cone of Vesuvius, 

 by a hill of smaller eminence, denominated 

 Monte Cantaroniy on which is the hermitage del 

 Salvatore. This hill is intersected by three val- 

 leys that deserve to be examined with attention, 

 on account of the quantity of primitive sub- 

 stances which the volcano has thrown thither, 

 during old eruptions. The northern valley is 

 that termed La Fossa di Pharaone near the plain, 

 and Vallone della Vetrana in its more elevated 

 part, where the current of lava flowed in 1785. 



473 







Somma. 



Valleys. 





