Royal Society. 127 
and the oil is ponderous, and finks in water 5 all which circum- 
ftances will contribute to a more conftant accenfion. 
Oleum Succini is juftly put in the catalogue of minerals, and is 
produced by a flrong degree of fire, yet it caules no motion, and 
Icarcely any incalelcence, notwithllanding it abounds in volatile 
falts^ the reafon is, becaufe thefe falts are not properly volatile, 
as alcr.li's are, but do belong to the family of acids, and fb can 
make no fermentation with this compound fpirit, which is itfelf 
highly acid. 
One furprifing effe£l of this fiery mixture was as follows 5 half 
a drachm of the oil of carvi-leed was poured into a fmall gally- 
pot, which was placed under a glafs that held three pints upon 
M. 'Papin's exhaufting engine, and having cleared it of air, the 
phial was turned up, in order to lee what effefl would enfue in 
this fort of Vacuum upon this mixture ; but in a moment the re- 
ceiver Wcis blown up, and the mixture in a flame 5 which was the 
more furprifing, as the honourable Mr. Soyk found that in all his 
experiments tlie removal of the air did almofl always extinguifli 
both light, fire, and flame. The blowing up of the glafs does 
alio make the experiment the more extraordinary, and puzzles 
one how to account for fo great a quantity of air, as was produced 
from thefe liquors, which amounted only to a drachm and a half • 
for here was required not only air fufficient to fill up the capacity 
of the veflel, but likewile h great a preflure within, as exceeded 
that great incumbent weight ,of air that prefled on this capacious 
glafs without, whole diameter was fix inches, and depth above 
eight, for otherwife it would not, have thrown it up into the air. 
This fiery mixture and gun-powder agree, in that both do heat, 
burn, and flame, and alfo do confiderably refifl: and raife up 
bodies that oppofe them; in both, the air is much agitated and 
expanded ^ but they differ, in that gun-powder will not be made 
to take fire, or make any explofion in Vacuo j that gun-powder is 
a compofition of the drielt and mofl: combuftible materials- 
whereas one of the two fluids is not eafily made to burn by itfelf^ 
and the other will extinguifli common fire^ that gun-powder 
requires a£iual fire to bring it to an accenfion 3 whereas in this 
you have only two liquors, both cold to the touch, that produce 
fire and flame by the bare joining and mixing them together. 
"the 
