the late Eruption of Mount Vesuvius. 107 
which we have had many examples during this eruption, par- 
ticularly of wood pigeons, that have been found dead on the 
lava. These vapours deposite a crust of sulphur, or salts, par- 
ticularly 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 sub- 
stance, exactly like the brightest steel or iron filings. 
The first appearance of the mofete, after the late eruption, 
was on the 17th of June, when a peasant going with an ass to 
his vineyard, a little above the village of Resina, in a narrow 
hollow way, the ass dropped down, and seemed to be expiring ; 
the peasant was soon sensible of the mephitic vapour himself, 
and well knowing its fatal effects, dragged the animal out of 
its influence, and it soon recovered. From that time these 
vapours have greatly increased, and extended themselves. 
There are to this day many cellars and wells, all the way from 
Portici to Torre dell' Annunziata, greatly affected by them. 
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 
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