VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. \J \ 



they arrived at the first screen, which was evident not only from their not setting 

 fire to the paper, which they sometimes did, but also from their being found stick- 

 ing in a soft board, against which they struck, after having passed through all the 5 

 screens; or leaving visible marks of their having impinged against it, and being 

 broken to pieces and dispersed by the blow. These pieces were often found lying 

 on the ground ; and from their forms and dimensions, as well as from other ap- 

 pearances, it was often quite evident that the little globe of powder had been on 

 fire, and that its diameter had been diminished by the combustion, before the fire 

 was put out on the globe being projected into the cold atmosphere. The holes 

 made in the screen by the little globe in its passage through them, seemed also to 

 indicate that its diameter had been diminished. 



That these globes or large grains of powder were always set on fire by the com- 

 bustion of the charge can hardly be doubted. This certainly happened in many of 

 the experiments, for they arrived at the screens on fire, and set fire to the paper ; 

 and in the experiments in which they were projected with small velocities, they 

 were often seen to pass through the air on fire ; and when this was the case no 

 vestige was to be found. They sometimes passed, on fire, through several of the 

 foremost screens without setting them on fire, and set fire to one or more of the 

 hindmost, and then went on and impinged against the board, which was placed at 

 the distance of 12 inches behind the last screen. It is hardly necessary for me to 

 observe, that all these experiments prove that the combustion of gunpowder is very 

 far from being so instantaneous as has generally been imagined *. I will just mention 

 one experiment more, in which this was shown in a manner still more striking, 

 and not less conclusive. A small piece of red-hot iron being dropped down into 

 the chamber of a common horse pistol, and the pistol being elevated to an angle of 

 about 45 degrees, on dropping down into its barrel one of the small globes of 

 powder, of the size of a pea, it took fire, and was projected into the atmosphere 

 by the elastic fluid generated in its own combustion, leaving a very beautiful train 

 of light behind it, and disappearing all at once, like a falling star. This amusing 

 experiment was repeated very often, and with globes of different sizes. When 

 very small ones were used singly, they were commonly consumed entirely before 

 they came out of the barrel of the pistol ; but when several of them were used to- 

 gether, some, if not all of them were commonly projected into the atmosphere 



on fire. 



I shall conclude this paper by some observations on the practical uses and improve- 

 ments that may probably be derived from these discoveries, respecting the great 

 expansive force of the fluid generated in the combustion of gunpowder. As the 

 slowness of the combustion of gunpowder is undoubtedly the cause which has pre- 



* It- is not surprizing that the burning of these solid globes or lumps of gunpowder should be different 

 from the same substance in the state of powder or small grains, its proper and useful state, in which the 

 fire can pass freely between the grains. The common case, of comparatively slow burning, in a sky- 

 rocket, when the powder is hard beaten together, nearly like the solid mass, is well known. 



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