100 PHILOSOPHICAL TRANSACTIONS. [ANNO 1781. 



vent atO, viz. 1764 feet in a second, and the square root of the other charges 

 expressed in grains. And the actual velocities are means of all experiments that 

 were made under similar circumstances. The 4th column shows the difference 

 of the computed and actual velocities, or the number of feet in a second by 

 which the actual velocity exceeds or falls short of the computed : and in the 5th 

 column is set down the number of experiments with each charge, from the 

 mean of which the actual velocity was determined. 



The agreement of the computed and actual velocities will appear more striking, 

 if we take the sum and difference of those velocities with all the charges except 

 the first : thus, 



Sum of the velocities, — 1764. 



, ^ , 



Computed. Actual. Difference. N°ofexp. 



SS6i 9S5i — 10 13 



So that it appears, that the difference, or the actual velocity, was smaller than 

 the computed by -54-5- P art on ly at a mean of 23 experiments. 



But as by far the greater number of the experiments were made with the fol- 

 lowing charges, viz. 2Q0, 218, 208, 165, and 145 grains of powder, let us 

 take the sum and difference of the computed and actual velocities of those 

 charges : thus, 



Sum of the velocities. 



. A. 



1 



Computed. Actual. Difference. N° of exp. 



5y85 6044 +59 IS 



Here the agreement of the theory with the experiments is so very remarkable, 

 that we must suppose it was in some measure accidental ; for the difference of 

 the velocities in repeating the same experiment, is in general much greater than 

 the difference of the computed and actual velocities in this instance ; but we 

 may fairly conclude, from the result of all these trials, that the velocities of like 

 musket bullets, when they are discharged from the same piece by different quan- 

 tities of the same kind of powder, are very nearly in the sub-duplicate ratio of 

 the weights of the charges. 



On the effect of placing the vent in different parts of the charge. — There have 

 been 2 opinions with respect to the manner in which gunpowder takes fire. Mr. 

 Robins supposes that the progress of its inflammation is so extremely rapid, 

 " that all the powder of the charge is fired and converted into an elastic fluid, 

 before the bullet is sensibly moved from its place ;" while others have been of 

 opinion that the progress of the inflammation is much slower, and that the 

 charge is seldom or never completely inflamed before the bullet is out of the 

 gun. The large quantities of powder that are frequently blown out of lire-arms 

 uninflamed, seem to favour the opinion of the advocates for the gradual firing ; 



