VOL. LXIX.] PHILOSOPHICAL TRANSACTIONS. 553 



whole mass, though always by succession. The quickness of this propagation 

 of fire depends in a great measure on the intervals or interstices which remain 

 among the grains of gunpowder, through which the particles of heated charcoal 

 are driven in every direction, together with the flame of the 2 airs. Hence gun- 

 powder reduced into impalpable powder, and rammed into a squib, does not in- 

 flame with an explosion, but burns slowly farther and farther, till the combustion 

 reaches the extremity of the squib, where it meets a mass of gunpowder in grains, 

 when immediately a loud explosion issues, by which the squib is shattered into 

 rags. Hence the size of the grains of gunpowder must be proportionate to the 

 size of the fire-arms to which it is destined, the greatest fire-arms requiring in 

 general grains of the largest size. 



If this wonderful and awful ingredient had not been discovered by accident^ 

 could the secret have escaped a long while the penetration of our modern philo- 

 sophers, who have found out the way of combining the air of the 2 constituents 

 after they had extricatecj^them, without any regard to the known properties of 

 gunpowder.' Nothing more was to be done than combinmg the 2 substances, 

 instead of combining the 2 airs first separated from them. 



Appendix. — In the foregoing paper I attempted to give a comparative view of 

 the explosive force of gunpowder and inflammable explosive air, which latter I 

 had found to be so far short of the explosive force of gunpowder, as not to con- 

 ceive any well grounded hope that it could ever become a substitute for this in- 

 gredient. At that time I had not yet tried the eflfect of very pure dephlogisti- 

 catedair, combined with that inflammable air into which I had found that vitriolic 

 aether is changed in an instant. I must acknowledge that I had but small expec- 

 tations from the force of these 2 airs combined ; for as I had always observed, 

 that aether air combined with common air is less brisk in taking fire, and less 

 powerful in exploding, than inflammable air extracted from the vitriolic or marine 

 acid, I thought that the same aether air combined with very pure dephlogisticated 

 air would also be less powerful than common inflammable air from metals. But 

 how far experience contradicted this theoretical analogy will be seen in the fol- 

 lowing lines. 



Abbe Fontana was so good as to assist me in this pursuit. Having produced 

 a good quantity of pure dephlogisticated air from red precipitate by heat, we first 

 filled a strong 2-ounce phial (the orifice of which was so wide that it could scarcely 

 be covered with the thumb, so that the bottle was almost cylindrical) with this air, 

 in the usual manner, by filling it first with water, inverting it, and letting the 

 air rise in it; which being done, we dropped one drop of aether (in which a small 

 quantity of camphire was dissolved) into it, and shut it immediately with the 

 thumb. After having given it some concussions, the orifice was applied to the 



VOL. XIV. 4 B 



