PRODUCTION OF SOUND IN VAPOUR. Jgn 



IT. 



Experiments on the Production of Sound in Vapour: by Mr, 



BlOT*. 



XA.N infinite number of experiments hfive been nriade on Production 

 the manner in which sound is produced and transmitted in ^"'^ transmis- 



j-rr ^ J- Til , 1 ■ • • 1 sion of sound 



ditterent mediums. Jt has been shown, that it is neither in vapour not 

 formed nor transmitted in a vacuum; and its transmission yetexammed. 

 through solids and liquids has been examined: but no one, 

 I believe, has yet thought of making these experiments in 

 vapour. Such an inquiry however is well calculated to ex- 

 cite our curiosity ; for, setting out with the results that ex- No sound 

 perience has made known with respect to the constitution should be pro- 



!• 1 1 /-ii • • fluced in va- 



oi the vapour that fills a given space, and applying to them pour, 

 the mathematical principles on which the laws of the minute 

 vibrations of elastic fluids are usually founded, it is evident, 

 that no sound should be produced in vapour. 



In fact it is shown, by the experiments of De Luc, Saus- Properties of 

 sure, and Dalton, that the quantity of vapour of water, or of ^*'^*'"'^' 

 any other liquid, that is formed in a vacuum, depends only 

 on the dimensions of that vacuum and the temperature : so 

 that, if this vapour have an elasticity capable of sustaining 

 the manometer at a certain height, and you compress it 

 slowly, so as to oblige it to occupy a smaller space, the elas- 

 ticity vvill not be increased l>y this compression, as that of a 

 permanent gas would be; but a portion of the vapour will 

 return to the liquid state, without any variation of the ma- 

 nometer; and only so much willremain, as isadapted to the 

 new limits, to which the vacuum is reduced. The reverse 

 will happen, if the space be enlarged instead of diminished : 

 a new quantity of vapour will be formed to fill it, but with- 

 out any change in the elasticity, or in the manometer. 

 These results have been completely established by the 

 learned gentlemen t have mentioned, and we may easily 

 convince ourselves of their accuracy. It is sufficient to in- 

 troduce into a bjjrometer a small quantity of any liquid; 

 and to measure the height at which the mercury stands, 



*M6m. de la Soc. d'Arcueil, vol. II, p. 94. Read to tha Institute, 

 Octoberlhe 12th, 1807. 



»fter 



