[ 675 ] 
dually intermixed, by the conftant more gradual 
Afcent of the warmer fulphurcous Vapours from the 
Earth, and Defcent of the cold ferene Air from 
above. And tho’ there was no luminous Flafh of 
Light in the Glafs, yet, when fuch fudden Effer- 
vefcence arifes, among a vaft Quantity of fuch Va- 
pours in the open Expanfe of Air, it may, not im- 
probably, acquire fo rapid a Velocity, as to kindle 
the fulphurcous Vapours, and thereby become lu- 
minous. 
And ftnee, from the EfFe&s that Lightning is ob- 
ferved to have on the Lunss of Animals, which it 
often kills, by deftroying the Air’s Elafticity in 
them, as alfo from its burfting Windows outwards, 
by deftroying the Air’s Elafticity on the Outfide of 
thofe Windows : Since, I fay, it is hence probable, that, 
the fulphurcous Pumes do deftroy a great Quantity 
ofclafticAir; it Ihould therefore caufe great Com- 
motions and Concufllons in the Air, when the Air 
rulhes into thofe evacuated Places 5 which it muft 
ncceflarily do with great Velocity. 
Dr. Tapinhas calculated the Velocity with which 
Air rufnes into an exhaufted Receiver, when driven 
by the whole Prdfure of the Atmofphere, to be at 
the Rate of 1305" Feet in a Second of Time; which 
is at the Rate of 889 Miles in an Hour : Which is 
near 18 times a greater Velocity than that of the 
ftrongeft Storms; which is eftimated to be at the 
Rate of yo Miles in an Hour *. : * . 
Hence 
* Phil. Tranf. n. 184, p. 195. LowthorpV Abridgment of Phil. 
Tranf. Vol.I. p. 586. 
Rrrr % 
