MIXED CASES* 



127 



t»f the relaxation or removal of that mechanical power, which 

 feeld (he gas in its fituation. Under all circumftances, there- 

 fore, when a gas efcapes from water, whether by placing the 

 aqueous mixture under an exhaufted receiver, or in an atraof- » 



phere of a different gas, the caufe operating its efcape, muft 

 be one and identical, viz. the diminution of mechanical pref- 

 fure. Before we account for any effed by comparifon of af- 

 finities, the affinities themfelves fliould be proved to exifl. 

 But with refpcd to the relation of gafe« to water, the proof 

 fails in every in (lance; for how can that efFed be fairly afcribed 

 to chemical affinity which is deftroyed, as is the connexion of 

 every gas with water, by an unmixed mechanical caufe; and 

 is it not abfurd to compare powers which have no exiftence in 

 nature? 



Admitting (hen the conne6lion between gafes and water to —and the pref- 

 be entirely dependent on phyfical prefTure, there naturally o"her'gas than 

 arifesout of this law an explanation of the curious fa6t, which that abtorbed. 

 I have afcertained, that each gas, when abforbed by water, is 

 retained in its place by an atmofphere of no other gas but of 

 its own kind. Under any other atmofphere, the abforbed gas 

 efcapes, even without agitation, though this certainly acce- 

 lerates the event. Now the fubaqueous gas can only accom- 

 plifh its change of place by virtue of fome a<5live principle or 

 power inherent in it, and caufing its movement; and this 

 power is its elafticity, which is not countera6ted by that of an 

 incumbent gas of a different fort. The fa6l affords, therefore, 

 fomething further than ** probability,'* that the particles of 

 gafes prefs only on thofe of their own kind ; for to fay that the 

 elafticity of the fubaqueous gas is not counteracted by any in- 

 cumbent one of a different fort, is to affert in other terms, that 

 the one is not preffed by the other, — the principle which I am 

 folicitoiis to eftabliHi. 



The above remarks are the only ones which I deem It within Jhe theory Is aa 

 my province to urge in reply to Mr. Gough. Before doling J-^^" . 'capable 

 this letter, however, I muft exculpate myfelf from the charge of mathematical 

 of attempting to uphold a mechanical theory, by probabilities J^^^fj^^^^"^^'^^_ 

 drawn from chemical fa6ls. This ftatement is notcorred; the fervatioji. 

 fa6ls which I have alledged are purely ftatical, and my obje6t 

 has been to prove that they were before erroneoufly included 

 winder the laws of chemical affinity, with which, in reality 

 they have no connexion, Thefe mechanical phenomena, I 



have 



