Experiments ^lpon Gunpowder. 43 



Of the Effect of placing the Vent in different Parts of the 



Charge. 



There have been two 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 fire-arms uninflamed seem to favour the 

 opinion of the advocates for the gradual inflammation ; 

 but Mr. Robins endeavors to account for that circum- 

 stance upon different principles ; and supports his opin- 

 ion by shewing that every increase of the charge, within 

 the limits of practice, produces a proportional increase 

 of the velocity of the bullet ; and that when the powder 

 is confined by a great additional weight, by firing two or 

 more bullets at a time, instead of one, the velocity is 

 not sensibly greater than it ought to be, according to 

 his theory. 



If this were a question merely speculative, it might 

 not be worth while to spend much time in the discus- 

 sion of it ; but as it is a matter upon the knowledge of 

 which depends the determination of many important 

 points respecting artillery, and from which ..many useful 

 improvements may be derived, too much pains cannot 

 be taken to come at the truth. Till the manner in 

 which powder takes fire and the velocity with which the 

 inflammation is propagated are known, nothing can with 



