[ 6 77 3 
like a Fog, were there a Wind : Which Difpcrfion 
would prevent the Earthquake; which is probably 
caus'd by the explofive Lightning of this fulphureous 
Cloud ; being both nearer the Earth than common 
Lightnings ; and alfo at a time when fulphureous 
Vapours are rifing from the Earth in greater Quan- 
tity than ufual; which is often occafion'd by a long 
Series of hot and dry Weather. In which com- 
bined Circumftances, the afcending fulphureous Va- 
pours in the Earth may probably take Fire, and 
thereby caufe an Earth-Lightning; which is at firft 
kindled at the Surface, and not at great Depths, as 
has been thought: And the Explofton of this Light- 
ning is the immediate Caufe of an Earthquake. 
It is in the like manner that thole Meteors, 
which are called falling Stars, are fuppofed to be 
kindled into a Flame at the upper Part of a ful- 
phureous Train, which is kindled downwards into 
a Flame, in the fame manner as a frefh-blown out 
Candle is inftantly lighted from another Candle held 
over it at a Diftance, in the fulphureous inflammable 
Smoke of it. 
I am fenfible that it may feem improbable, that 
the afcending fulphureous Vapours in the Earth 
fhould thus be kindled ; but, fince they are conti- 
nually afcending thro' the Pores of the Earth, more 
or lefs, for many good and ufeful Purpofes, it is plain 
there is Room for them to pafs. Befides, as Monf. 
de Buffon remarks, Naturalifts have obferved per- 
pendicular and oblique Clefts, in all Kinds of Layers 
of Earth, not only among Rocks, but alfo among all 
Kinds of Earth, that have not been removed, as is ob- 
fervable wherever the Earth is open to any Depth. Now 
thefe 
