504 PHILOSOPHICAL TRANSACTIONS. [aNNO 1795. 



have expired if they had not been hastily removed. These occasional vapours, 

 and which are called here inofete, are of the same 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 this country 

 are called fumaroli, are of another nature, and issue from spots all over the 

 fresh and hot lavas while they are cooling ; they are sulphureous and suffocating, 

 so much so that often the birds that are flying over them are overpowered, and 

 fall down dead. These vapours deposit a crust of sulphur, or salts, particularly 

 of sal ammoniac on the scoriae of the lava through which they pass ; and the 

 small crystals of which they are composed are often tinged with a deep or pale 

 yellow, with a bright red like cinnabar, and sometimes with green, or an azure 

 blue. Since the late eruption, many pieces of the scoriae of the fresh lava have 

 been found powdered with a lucid substance, exactly like the brightest steel or 

 iron filings. This heavy vapour, when exposed to the open air, does not rise 

 much more than a foot above the surface of the earth ; but when it gets into a 

 confined place, like a cellar or well, it rises and fills them as any other fluid 

 would do ; having filled a well, it rises above it about a foot high, and then 

 bending over, falls to the earth, on which it spreads, always preserving its usual 

 level. Wherever this vapour issues, a wavering in the air is perceptible, like 

 that which is produced by the burning of charcoal ; and when it issues from a 

 fissure near any plants or vegetables, the leaves of those plants are seen to move, 

 as if they were agitated by a gentle wind. It is extraordinary, that though there 

 does not appear to be any poisonous quality in this vapour, which in every re- 

 spect resembles fixed air, it should prove so very fatal to the vineyards, some thou- 

 sand acres of which have been destroyed by it since the late eruption ; when it 

 penetrates to the roots of the vines, it dries them up, and kills the plant. A 

 peasant in the neighbourhood of Resina having sufii'red by the mofete, which 

 destroyed his vineyards in the year 1767, and having observed then that the va- 

 pour followed the laws of all fluids, made a narrow deep ditch all round his vine- 

 yard, which communicated with ancient lavas, and also to a deep cavern under 

 one of them : the consequence of his well reasoned operation has been, that 

 though surrounded at present by these noxious vapours, and which lie constantly 

 at the bottom of his ditch, they have never entered his vineyard, and his vines 

 are now in a flourishing state, while those of his neighbours are perishing. 

 Upwards of 1300 hares, and many pheasants and partridges, overtaken by this 

 vapour, have been found dead within his Sicilian Majesty's reserved chases in the 

 neighbourhood of Vesuvius ; and also many domestic cats, who in their pursuit 

 after this game fell victims to the mofete. A few days ago a shoal of fish, of 

 several liundred weight, having been observed by some fishermen at Kesina in 

 great agitation on the surface of the sea, near some rocks of an ancient lava 



