358 Mephitic Vapours [Book VI. 



coul'd not be faid to have finimed, although the force 

 of it was over the 22d of June. The power of 

 attraction in mountains is well known ; but whether 

 the attractive power of a volcanic mountain is greater 

 than that of any other mountain, is a queftion. Dur- 

 ing this eruption, however, it appeared that every 

 watery clcud was evidently attracted by Vefuvius, and 

 the fudden diflblution of thofe clouds left marks of 

 their dcftructive power on the face of the country all 

 round the bafis of the volcano. After the mouth of 

 Vefuvius was enlarged, our author fays he has feen 

 a great cloud pafling over it, and which not only was 

 attracted, but was fucked in, and difappeared in a mo- 

 ment. 



After every violent eruption of Mount Vefuvius, 

 we read of damage done by a mephitic vapour, which 

 coming from under the ancient lavas, infmuates itfelf 

 into low places, fuch as the cellars and wells of the 

 houfes fituate at the foot of the volcano. After the 

 eruption of 1767, there were feveral inftances, as in 

 this, of people going into their cellars at Portici, and 

 other parts of that neighbourhood, having been ftruck 

 down by this vapour, and who would have expired if 

 they had not been haftily removed. Thefe occafional 

 vapours, or mofete, are of the fame quality as that 

 permanent one in the Grotta del Cane, near the lake 

 of Agnano, and which has been proved to be chiefly 

 fixed air. The vapours, that in the volcanic language 

 of Naples, are called fumaroli, are of another na- 

 ture, and iffue from fpots all over the frefh and hot 

 lavas while they are cooling ; they are fulphureous 

 and fo fuffocating, that often the birds which are 

 flying over them are overpowered, and fall down 

 dead. Thefe vapours depofit a cruft of fulphur, or 

 fains, particularly of fal ammoniac, on the fcorise of 

 I the 



