( 4 10 ) 
rarified exceedingly by fubterraneous Fire, and tinged with 
fulfureous Steams ; which Vapour is now generally 
taken by our Naturalids to be the Caufe of Earthquakes. 
And as Earthquakes happen with great Uncertainty, 
and have been fometimes frequent in Places, where for 
many Years before and after they have not been felt ; fo 
Thefe, which we might be allowed to fuppofe produced 
by the Eruption of the pent Vapour through the Pores of 
the Earth, when it is not in fufficient Quantity, nor hid- 
den enough tolhake its Surface, or to open it felf a Paf- 
fage by rending it. And as thefe Vapours arefuddenly 
produced by the Fall of Water upon the nitro-fulphurous 
Fires under Ground, they might well be thought to get 
from thence a Tindure which might difpofe them to 
fhine in the Night, and a Tendency contrary to that of 
Gravity; as we find the Vapours of Gun-powder, when 
heated in Vacuo, to (liine in the Dark, and afeend to the 
Top of the Receiver though exhauded : the Experiment 
of which I faw very neatly performed by Mr. J. Whitefidt 
Keeper of Afhmole* s Mufeum in Oxford. 
Nor fhould I feek for any other Caufe than this, if in 
fome of thefe Inftances, and particularly this whereof we 
treat, the Appearance had not been feen over a much 
greater Part of the Earth’s furface that can be thus accoun- 
ted for. It having in this lad been vifible from the Wed 
Side of Ireland to the Confines of RuJ/iatmd Polandoo the 
Ead (nor do we yet know its Limits on that SideJ exten- 
ding over at lead thirty Degrees of Longitude ; and in 
Latitude, from about fifty Degrees over almod all the 
North of Europe ; and in all Places exhibiting at the 
fame time the fame wonderous Circumdances, as we are 
informed by the Publick News- Now this is a Space much 
coo wide to be lhaken at any one Time by the greated 
of Earthquakes, or to be affeded by the Perfpiration 
of that Vapour, which being included and wanting vent, 
might 
