Royal Society, 125 
as are made out of the leeds are diilinguiflied from thofe made out 
of the trunks, bark, roots, or any other part of the vegetable j 
there is farther a difference obfcrved between thofe feeds, that 
have only a fragrant fmell, and a pungent talte only, and thofe 
that have both odorous effluvia and a brilk tafte, and alfb thofe 
that are infipid, and have no fmart tafte. In the firft place we 
muft iet afide thofe oils made by expreffion, for having tried oil 
of linfeed, of nuts, of olives, of almonds, ^r. they would nei- 
ther make an explofion er ebullition, or lb much as any fermenta- 
tion with the compound fpirit of nitre ^ nor could they be brought 
to incorporate without much ftirring^ and when they did unite, 
the heat was but juft: lenfible. To examine briefly the mineral 
oils, there are fome, as oil of vitriol, oil of i\x]^hur per Campa- 
tiam^ that have not any property of oils, but are rather acids and 
corroding menftruums; there are others which have the true pro- 
perty of effential oils, as oleum 'Petreoliy and Barbados tar 
highly re6tified, which do not produce any remarkable heat, 
much lefs an ebullition or exploiion, nor does that atiive oil of 
amber do any thing mor^; the itillatitious oil of bees- wax had 
much the fame effe6l, when incorporated with the compound 
fiery fpirit 5 and this makes it probable that wax itlclf may be a 
compound rather of a mineral than vegetable nature. Now of 
thole eflential oils, which produce a great ebullition, explofion, 
and flame with the compound fpirit there are two Ibrts, vegetable 
and animal 5 the true vegetable effential oils do all of them make 
a violent ebullition and explofion, and feveral of them actually 
take fire and flame, as the catalogue of experiment fpecifies. If 
it be inquired into, what (hare the oil has in producing this fire» 
whether it be only a pabulum or fuel, for the fpirit to actuate, and 
fo be merely paffive ? Or whether it contributes any particles that 
help to excite this flame ? In order to the refolving this doubt, we 
are to confider, that thefe effential oils are produced from ^t^ds^ 
that have very active or warm parts or fpirits, luch as will eafily 
ferment and heat • and befides the potential heat of the vegetable, 
eflential oils contain a volatile lalt, which gives much of that 
pungency to the tafte 5 therefore thele oils are not a bare pabulum 
ignis y or an una£live principle, but do on a double account, as 
well on the fcore of the incalefcent oil as of the inherent faltj?, 
coni'pire with the compound fpirit to make this great heat, explofion 
and accenfion. In the catalogue of experiments, we may farther 
oblerve, that of the light eflential oils drawn from feeds of vege- 
tables, all of them do make a great ebullition with an explofion 
but that few of them do n^^ually take fire- and that all thole, 
ex- 
