( 54» ) 
it 5 and confequentfy the weight of i8 grains of Powder did 
yield Air. enough to fill the eighteenth part of a Receiver that 
contains feven pound of water. Now, this eighteenth part con- 
tains 49 drachms of water : Wherefore the'Air , that takes up an 
equal fpace, being 1000 times lighter , weighs ^ of 49 drachms, 
which is more than 3I grains. It follows therefore, that the 
weight of Ingrains of Powder which 1 employed in my Experi- 
ment, contained more than 3^ of Air, which is about the fifth pare 
of eighteen grains. 
It may alfo be calculated , how many times this Air hath been 
compreffedin the Powder : But this calculation is more uncer- 
tain than the former, becaufe we know not, whether this Air took 
up more or lefs than the fifth part of the fpace which the Powder 
poflfeflTed. But yet 'tis certain, that, though it had even taken up 
r/?w/tf»r/^iof the whole room of the Powder, and that the four- 
teen grains of the other matter had taken up no more than the one 
remaining fourth part , ftill this Air would have been compreffed 
about three hundred times* To calculate this , I fuppofe, that 
the fpace of a Cubic foot can hold only 72 pound of Gunpowder, 
which do contain more than 14 pound of Air, by the foregoing 
ulculm ; which quantity of Air is therefore found inclofed in the 
three fourths of a Cubic foot. Now, this fpace doth ufually con- 
tain but about fix drachms of Air: Wherefore, to make it hold 
fourteen pound of Air , which is near three hundred times fix 
drachms , it mu(t needs be, that that Air be compreffed near three 
hundred times. ' 
There is reafon to believe, that this Compreflion is much 
greater, becaufe a Cubic foot can hold much more thanfeventy 
tAvo pound of Powder, and becaufe alfo that the ^J/^ir^ part of the 
weight muft not , in appearance , poffefs alone the three fourths^ 
and all the refl: take up no more than me fourth of the fpace pof- 
fefled by all the Powder. 
I fliould therefore make no difficulty to believe , that all the 
tffeft of Gunpowder comes from the Air which is compreffed 
therein, and efpecially in the Saltpeter j for I have not ob- 
ferved, that Brimftone yields Air. Poflibly alfo we may find in 
time, that all other Fulmlnations , Ebullitions and Fermentations, 
that make fuch furprizing motions , are nothing elfe but Air com- 
preffed expanding it felf. 
An 
