1during his ſtay in Malta, he often ſaw
Mount Ætna, though the next day, not
withſtanding its being extreamly clear, he
could not ſee it; adding, that Vintemillius,
a very Learned Perſon, did oftentimes,
from a Hill he names, behold the whole
Iſland he calls Luprica protuberant above
the Sea, though at other times, notwith
ſtanding a clear Sky, he could not ſee it.
And though perhaps this may be in part a
ſcribed to the various light & poſition of
the ſun, or to the various diſpoſition of the
Spectators eye, or peradventure to ſome
other cauſe; yet the moſt probable cauſe
ſeems to be the differing Denſity of the
Air, occaſion'd by Exhalations capable to
increaſe the refraction, and conſequently
bring Beams to the Eye, which otherwiſe
would not fall on it. We have likewiſe
in another Treatiſe mention'd our having
often obſerv'd with Teleſcopes a plenty
of Steams in the Air, which without ſuch
a help would not be taken notice of, and
which as they were not at all times to be
ſeen even through a Teleſcope, ſo they
did ſometimes, eſpecially after a ſhower of
Rain, haſtily diſappear: and when we
have viſited thoſe places that abound with
Mines, we have ſeveral times been told
Mount Ætna, though the next day, not
withſtanding its being extreamly clear, he
could not ſee it; adding, that Vintemillius,
a very Learned Perſon, did oftentimes,
from a Hill he names, behold the whole
Iſland he calls Luprica protuberant above
the Sea, though at other times, notwith
ſtanding a clear Sky, he could not ſee it.
And though perhaps this may be in part a
ſcribed to the various light & poſition of
the ſun, or to the various diſpoſition of the
Spectators eye, or peradventure to ſome
other cauſe; yet the moſt probable cauſe
ſeems to be the differing Denſity of the
Air, occaſion'd by Exhalations capable to
increaſe the refraction, and conſequently
bring Beams to the Eye, which otherwiſe
would not fall on it. We have likewiſe
in another Treatiſe mention'd our having
often obſerv'd with Teleſcopes a plenty
of Steams in the Air, which without ſuch
a help would not be taken notice of, and
which as they were not at all times to be
ſeen even through a Teleſcope, ſo they
did ſometimes, eſpecially after a ſhower of
Rain, haſtily diſappear: and when we
have viſited thoſe places that abound with
Mines, we have ſeveral times been told
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