Page:Philosophical Transactions - Volume 029.djvu/433

 rarified exceedingly by ſubterrancous Fire, and tinged with ſulfureous Steams; which Vapour is now generally taken by our Naturaliſts to be the Cauſe of Earthquakes. And as Earthquakes happen with great Uncertainty, and have been ſometimes frequent in Places, where for many Years before and after they have not been felt; ſo Theſe, which we might be allowed to ſuppoſe produced by the Eruption of the pent Vapour through the Pores of the Earth, when it is not in ſufficient Quantity, nor ſudden enough to ſhake its Surface, or to openit ſelf a Paſſage by rending it. And as theſe Vapours are ſuddenly produced by the Fall of Water upon the nitro-ſulphurous Fires under Ground, they might well be thought to get from thence a Tincture which might diſpoſe them to ſhine in the Night, and a Tendency contrary to that of Gravity; as we find the Vapours of Gun-powder, when heated in Vacuo, to ſhine in the Dark, and aſcend to the Top of the Receiver though exhauſted: the Experiment of which I ſaw very neatly performed by Mr. F. Whitefide Keeper of Ambmole’s Muſeum in Oxford.

Nor ſhould I ſeek for any other Cauſe than this, if in ſome of theſe Inſtances, and particularly this whereof we treat, the Appearance had not been ſeen over a much greater Part of the Earth’s ſurface that can be thus accounted for. It having in this laſt been viſible from the Weſt Side of Ireland to the Confines of Ruſſia and Poland on the Eaſt (nor do we yet know its Limits on that Side) extending over at leaſt thirty Degrees of Longitude; and in Latitude, from about fifty Degrees over almoft all the North of Europe; and ia all Places exhibiting at the ſame time the ſame wonderous Circumſtances, as we are informed by the Publick News. Now this is a Space much too wide to be ſhaken at any one Time by the greateſt of Earthquakes, or to be affected by the Perſbiration of that Vapour, which being included and wanting vent,