844 ' •W'*' Theory of the ConfUutlort of mixed Aenfofm Fluids, 



fulphuret of pot-afli, the oxigenous gas in a fliort time is almoft wholly abforbed: now it Is 

 not eafy to conceive how any chemical affinity fliould operate upon a body at the diftance 

 perhaps of 12 inches or more. The fa6l is, the fulphur abforbs the oxigen in conta£l with 

 it ;. and as the remainder of the gas expands to fill up the vacuity, ic is fucceflively abforbed 

 in the fame way. A fimilar abforption takes place, when a quantity of any gas containing 

 aqueous vapour is confined along with fulphuric acid, or dry, deliquefcent falts ; the va- 

 pour is abforbed, and the mafs is dlminiflied in elafticity, notwithftanding the fuppofed 

 chemical affinity of thegafes for water. 



Lavoifier's defcription of the atmofphcre therefore appears to be too limited, when he 

 fays, *' Our atmofphere is a compound of all the fluids which are fufceptible of the vaporous 

 or .permanently elaftic ftate, in the ufual temperature, and under the common preffure :" 

 this laft limitation fliould be omitted. The general atmofphere feems to be a compound of 

 four fluids principally, or four particular atmofpheres ; a7.otic gas, which at a medium 

 prefles the earth's furface with a force equal to 21.2 inches of mercury ; oxigenous, gas, which 

 is ufually equal to 7.8 inches; aqueous vapour, which varies from 1 inch to .1, or lefs, ac- 

 cording to climate and feafon ; and carbonic acid gas, the prefliire of which may perhaps be 

 equal to i inch. Tliofe gafes and vapour prels feparatcly on the furface of the earth ; and 

 any one of them may be withdrawn, or another added to the number, without materially 

 difturbing the reft, or any way afFe£l:ing their denfity. 



The above do£trine neceflarily requires the force of vapours from any fluid to depend 

 folely upon temperature, and confequently to be the- fame in any gas as in an exhaufted re- 

 ceiver. This I had proved to be the fa£t with feveral fluids, before this theory occurred 

 to explain the. reafon. I intend to give, fome account of the experiments relating to this 

 fubjeft, and to evaporation in general, in a volume of Memoirs of the Manchefter's 

 Literary and Philofophical Society, now in the prefs ; together with fome experiments oq 

 the expansion of gafes by heat, controverting certain refults of Guyton and Du Vernois, 

 in the Jnnales de Chimie, Vol. I. 



The very important changes in our views of fa£ls in chcmiftry, meteorology, &c. which 

 the principles here advanced will make if adopted ; and the ftriking manner in which they 

 appear to mc to refolve what have juftly been conCdcrcd as fome of the greateft difficulties, 

 muft be my apology for defiring thefe obfervations to be communicated as foon as coa- 

 veuient. 



I am, 

 Withrefpeft, &c. 



JOHN D ALTON. 

 Manchepr, Sept. 14, 180 1. 



On 



