60 Experiments upon Gunpowder. 



the pendulum was but small, and a small mistake in 

 measuring the chord upon the ribbon would have pro- 

 duced a very considerable error in computing the ve- 

 locity of the bullet ; thus, a difference of one tenth of an 

 inch, more or less, upon the ribbon in the 85th experi- 

 ment would have made a difference in the velocity of 

 more than 120 feet in a second. But independent of 

 the pains that were taken to prevent mistakes, the strik- 

 ing agreement of the velocities determined by the two 

 methods in the experiments which immediately follow, 

 as also in all other cases where they could be compared, 

 affords abundant reason to conclude that the errors 

 arising from those causes were in no instance very con- 

 siderable. 



But if both methods of ascertaining the velocities of 

 bullets are to be relied on, then the difference of the 

 velocities, as determined by them, in these experiments, 

 can only be accounted for by supposing that it arose 

 from their having been diminished by the resistance of 

 the air in the passage of the bullets from the mouth 

 of the piece to the pendulum ; and this suspicion will 

 be much strengthened when we consider how great the 

 resistance is that the air opposes to bodies that move 

 very swiftly in it, and that the bullets in these experi- 

 ments were not only projected with great velocities, but 

 were also very light, and consequently more liable to be 

 retarded by the resistance on that account. 



To put the matter beyond all doubt, let us see what 

 the resistance was that these 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 second. 



