126 On the Liquefaction of Gases. [1S24. 



In another place it is said, " What was very remarkable in 

 all these 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 upon raising the weight by means 

 of its lever, and suffering this vapour to escape, instead of 

 escaping with a loud report it rushed out with a hissing noise, 

 hardly so loud or so sharp as the report of a common air-gun, 

 and its effects against the leather stopper, by which it assisted 

 in raising the weight, were so very feeble as not to be sensible." 

 This the Count attributes to the formation of a hard mass, like 

 a stone, within the cylinder, occasioned by the condensation of 

 what was, at the moment of ignition, an elastic fluid. Such a 

 substance was always found in these cases ; but when the ex- 

 plosion raised the weight and blew out the stopper, nothing 

 of this kind remained. 



The effects here described, both of elastic force and its cessa- 

 tion on cooling, may evidently be referred as much to carbonic 

 acid and perhaps other gases as to water. The strong sudden 

 hissing observed as occurring when only a little of the products 

 escaped, may have been due to the passage of the gases into the 

 air, with comparatively but little water, the circumstances being 

 such as were not sufficient to confine the former, though they 

 might the latter ; for it cannot be doubted but that in similar 

 circumstances the elastic force of carbonic acid would far sur- 

 pass that of water. Count Rumford says, that the gunpowder 

 made use of, when well shaken together, occupied rather less 

 space than an equal weight of water. The quantity of residuum 

 before referred to, left by a given weight of gunpowder, is not 

 mentioned, so that the actual space occupied by the vapour of 

 water, carbonic acid, &c., at the moment of ignition, cannot be 

 inferred ; there can, however, be but little doubt that when 

 perfectly confined they were in the state of the substances in 

 M. Cagniard de la Tour's experiments*. 



When allowed to remain a few minutes, or even seconds, the 



expansive force at first observed diminished exceedingly, so as 



scarcely to surpass that of the air in a charged air-gun. Of 



course all that was due to the vaporization of water and some 



* See Quarterly Journal of Science, vol. xv. p. 145. 



