VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 151 



What was very remarkable in all those experiments in which the generated elastic 

 vapour was completely confined, was the small degree of expansive force which this 

 vapour appeared to possess after it had been suffered to remain a few minutes, or 

 even only a few seconds, confined in the barrel : for, on raising the weight by 

 means of its lever, and suffering this vapour to escape, instead of escaping with a 

 loud report, it rushed put with a hissing noise hardly so loud or so sharp as the re- 

 port of a common air-gun ; and its efforts against the leathern stopper, by which it 

 assisted in raising the weight, were so very feeble as not to be sensible. On exa- 

 mining the barrel however, this diminution of the force of the generated elastic 

 fluid was easily explained ; for what was undoubtedly in the moment of the ex- 

 plosion in the form of an elastic fluid, was now found transformed into a solid body 

 as hard as a stone ! It may easily be imagined how much this unexpected appear- 

 ance excited my curiosity ; but, intent on the prosecution of the main design of 

 these experiments, the ascertaining the force of fired gunpowder, I was determined 

 not to permit myself to be enticed away from it by any extraordinary or unexpected 

 appearances, or accidental discoveries, however alluring they might be ; and, faith- 

 ful to this resolution, I postponed the examination of this curious phenomenon to a 

 future period ; and since that time I have not found leisure to engage in it. I think 

 it right however, to mention in this place such cursory observations as I was able, 

 in the midst of my other pursuits, to make on this subject ; and it will afford me 

 sincere pleasure, if what I have to offer should so far excite the curiosity of philo- 

 sophers, as to induce some one who has leisure, and the means of pursuing such 

 inquiries with effect, to precede me in the investigation of this interesting pheno- 

 menon ; and as the subject is certainly not only extremely curious in itself, but bids 

 fair to lead to other and very important discoveries, I cannot help flattering myself 

 that some attention will be paid to it. I have said^ that the solid substance, into 

 which the elastic vapour generated in the combustion of gunpowder was trans- 

 formed, was as hard as a stone. This I am sensible is but a vague expression ; but 

 the fact is, that it was very hard, and so firmly attached to the inside of the barrel, 

 and particularly to the inside of the upper part of the vent tube, that it was always 

 necessary, in order to remove it, to make use of a drill, and frequently to apply a 

 considerable degree of force. This substance, which was of a black colour, or 

 rather of a dirty grey, that changed to black on being exposed to the air, had a 

 pungent, acrid, alkaline taste, and smelt like liver of sulphur. It attracted moisture 

 from the air with great avidity. Being moistened with water, and spirit of nitre 

 being poured on it, a strong effervescence ensued, attended by a very offensive and 

 penetrating smell. Nearly the whole quantity of matter of which the powder was 

 composed, seemed to have been transformed into this substance ; for the quantity 

 of elastic fluid which escaped on removing the weight, was very inconsiderable : but 

 this substance was no longer gunpowder ; it was not even inflammable. What change 

 had it undergone ? what could it have lost ? It is very certain that the barrel was 



