{ ) 
by boiliflg, and lefs Degrees of'Heat, changed into 
an elaftick Vapour rare enough to rife in Air, Oils 
and Quickfilver in Diftillation made to rife in a 
very rare Medium, fuch as remains in the red-hoc 
Retort, and fulphureous Steams will rife even in an 
exhaufted Receiver, as the Matter of the Aurora 
Borealis does in the thinner Part of our Atmo- 
fpherc. If Aqua-fortis be poured on Quickfilver, 
a reddilh Fume will rife much lighter than common 
Air ; fo alfo will Fumes rife from Filings of Metals, 
from Vegetables when they ferment by Putrefa< 3 :ion ; 
and (as the Reverend Mr. Hales has fliewn) feve- 
ral folid Subftances by diftilling, as wxll as Fer- 
mentation, will generate permanent Air. 
That Fieat will add Elafticity to Fluids is evi- 
dent from numberlefs Experiments, efpecially from 
Diftilling and Chymiflry ; But what is needful to 
confider here is only, that it a6ts more powerfully 
on Water than common Air ; for the fame Heat 
which rarefies Air only |. will rarefy Water very 
near 14000 times, changing it into Steam or Va- 
pour as it boils it : And in Winter, that fmall De- 
gree of Hear, which in Refped: to our Bodies ap- 
pears cold, will raife a Steam or Vapour from Wa- 
ter at the fame Time that it condenfes Air. 
By a great many Obfervations made by Mr. 
Henry Beighton^ F. R. S. and my felfi upon the 
Engine to raife Water by Fire, according to Mr. 
Newcomen's Improvement of it; we found that the 
Water in boiling is expanded 14000 times to gene- 
rate a Steam as flrong (i. e. as elaftick) as common 
Air, which therefore mnft be near i6\ times fpe- 
cificalJy 
