72 Experiments tipon Gunpozvder. 



be best to begin by firing the piece two or three times, 

 merely to warm it ; after which three or four experi- 

 ments may be made with standard powder, to determine 

 anew the proof mark (for the strength of the same pow- 

 der is different upon different days) ; and when this is 

 done, the experiments with the powder that is to be 

 proved are to be made, taking care to preserve the same 

 interval of time between the firings, that the heat of the 

 piece may be the same in each trial. 



If all these precautions are taken, and if the bullets 

 are of the same weight and dimensions, powder may be 

 proved by this method with much greater accuracy than 

 has hitherto been done by any of the methods hitherto 

 used for that purpose. 



Of the comparative Goodness^ or Value, of Powder of dif- 

 ferent Degrees of Strength. 



Let V denote the velocity of the bullet with the stronger 

 powder, and put v equal to the velocity with the weaker, 

 when the charges are equal, and the weight and dimen- 

 sions of the bullets are the same, and when they are 

 discharged from the same piece. If the charge is aug- 

 mented when the weaker powder is made use of, till the 

 velocity of the bullet is increased from v to V, or till it 

 becomes equal to the velocity with the given charge of 

 the stronger powder, the value of the charges may then 

 be said to be equal ; and consequently the weaker pow- 

 der is as much worse than the stronger — or is of less 

 value — in proportion as the quantity of it, by the 

 pound, required to produce the given effect is greater. 



But we have seen that the velocities, with different 

 quantities of the same kind of powder, are in the sub- 

 duplicate ratio of the weights of the charges. The 



