398 Dr. ingenhousz’s Account of a 
feen in the Memoire of Count saluce, inferted in the 
Melanges de Philofophie et de Matbematiques de l' Acad. 
Royale de Turin). The fulphur feems to ferve only for 
the purpofe of fetting fire to the mafs with a lefs degree 
of heat. 
Nitre yields by heat a furprizing quantity of pure de- 
phlogifticated air. Charcoal yields by heat a confidera- 
ble quantity of inflammable air. The fire employed to 
inflame the gunpowder extricates thefe two airs, and fets 
fire to them at the fame inftant of their extrication. 
Thus the difference between the inflammation of gun- 
powder and that of a mixture of inflammable air with 
dephlogifticated air in an ordinary air piftol (as thefe laft 
are now contrived for a philofophical amufement) feems 
to be, that the compound of the two airs in the air piffol 
takes fire, when already extricated and exifting in a fpace 
without compreflion or condenfation ; that is to fay, 
when they are in no condition of exerting a much 
greater elafticity than what they acquired by the heat 
generated in the moment of their explofion ; which heat 
can only expand them to four times their former bulk, 
according to Mr. robins : whereas in gunpowder the two 
airs, exifting in a folid ftate before their extrication, and 
occupying, according to Mr. robins, about of the 
fpace they take up after they are fet loofe, but rnoft pro- 
bably 
