upon Gun-powder? &c. 291 
will be much ftrengthened when we confider how great the 
refiftance is that the air oppofes to bodies that move very fwiftly 
in it, and that the bullets in thefe experiments were not only 
projected with great velocities, but were alfo very light, and 
confequentiy more liable to be retarded by the refinance on that 
account. 
To put the matter beyond all doubt, let us fee what the re- 
fiftance was that thefe bullets met with, and how much their 
velocities were diminished by it. The weight of the bullet (in 
the 85th experiment) was 90 grains ; its diameter was 0,78 of 
an inch, and it was projected with a velocity of 2109 feet in a 
fecond. 
If now a computation be made according to the method laid 
down by Sir Isaac newton for comprelfed fluids, it will be 
found, that the refiftance to this bullet was not lefs than 8f 
lbs. avoirdupois, which is fomething more than 660 times Its ^ 
weight. But Mr. robins has fhewn, by experiment, that 
the refiftance of the air to bodies moving in it with very great: 
velocity is near three times greater than Sir Isaac has 
determined it, and as the velocity with which this bullet was 
impelled is confiderably greater than any in Mr. robins’s expe- 
riments, it is highly probable, that the refiftance in this in- 
ftance was at leaft 2000 times greater than the weight of the 
bullet. 
The diftance from the mouth of the piece to the pendulum,, 
as we have before obferved, was 12 feet;, but, as there is rea- 
fon to think, that the blaft of the powder, which always fol- 
lows the bullet, continues to aft upon It for fome fenfible fpace 
of time after it is out of the bore, and by urging it on coun- 
ter-balances, or at leaft counter-afts in a great meafure the 
refiftance of the air, we will fuppofe, that the refiftance does 
1 not 
