170 PHILOSOPHICAL TRANSACTIONS. [ANNO 1/97. 



It is a fact well known, that on the discharge of fire-arms of all kinds, cannon 

 and mortars as well as muskets, there is always a considerable quantity of uncon- 

 sumed grains of gunpowder blown out of them; and, what is yery remarkable, 

 and, as it leads directly to a discovery of the cause of this effect, is highly de- 

 serving of consideration, these unconsumed grains are not merely blown out of the 

 muzzles of fire-arms; they come out also by their vents or touch-holes, where the 

 fire enters to inflame the charge; as many persons who have had the misfortune to 

 stand with their faces near the touch-hole of a musket, when it has been discharged, 

 have found to their cost. Now it appears to me to be extremely improbable, if 

 not absolutely impossible, that a grain of gunpowder actually in the chamber of 

 the piece, and completely surrounded by flame, should, by the action of that very 

 flame, be blown out of it, without being at the same time set on fire. But if these 

 grains of powder are actually on fire when they come out of the piece, and are af- 

 terwards found at a distance from it unconsumed, this is, in my opinion, a most 

 decisive proof, not only that the combustion of gunpowder is by no means so rapid 

 as has generally been thought to be, but also, what will doubtless appear quite in- 

 credible, that if a grain of gunpowder, actually on fire, and burning with the 

 utmost violence over the whole extent of its surface, be projected with a very great 

 velocity into a cold atmosphere, the fire will be extinguished, and the remains of 

 the grain will fall to the ground unchanged, and as inflammable as before. 



This extraordinary fact was ascertained beyond all possibility of doubt by the fol- 

 lowing experiments. Having procured from a powder-mill in the neighbourhood 

 of the city of Munich a quantity of gunpowder, all of the same mass, but formed 

 into grains of very different sizes, some as small as the grains of the finest Battel 

 powder, and the largest of them nearly the size of large pease, I placed a number 

 of vertical screens of very thin paper, one behind another, at the distance of 

 12 inches from each other; and loading a common musket repeatedly with this 

 powder, sometimes without, and sometimes with a wad, I fired it against the fore- 

 most screen, and observed the quantity and effects of the unconsumed grains of 

 powder which impinged against it. The screens were so contrived, by means of 

 double frames united by hinges, that the paper could be changed with very little 

 trouble, and it was actually changed after every experiment. The distance from 

 the muzzle of the gun to the first screen was not always the same; in some of the 

 experiments it was only 8 feet, in others it was 10, and in some 12 feet. The 

 charge of powder was varied in a great number of different ways, but the most in- 

 teresting experiments were made with one single large grain of powder, propelled 

 by smaller and larger charges of very fine-grained powder. 



These large grains never failed to reach the screen ; and though they sometimes 

 appeared to have been broken into several pieces, by the force of the explosion, yet 

 they frequently reached the first screen entire; and sometimes passed through all 

 the screens, 5 in number, without being broken. When they were propelled by 

 large charges, and consequently with great velocity, they were seldom on fire when 



