272 ON MIXED GASES* 



Obfervations on precifion with Mr. G. ; but it would have been more intelli* 

 letter orTmixcd ^'^^^ ^^ "^® '^ ^^ ^^^^ flated the objefts of his reply thus: 

 gafes, fj?, A refutation of Mr. D.'s arguments in favour of his 



fydcm. 



2d, An anfvver to his objecStions brought againfl mine. 



3d, New objedions to his fyftem. 



The firft thing worthy of notice is the objedlion to my ar- 

 gument for the mutual penetrability of gafes, I have afTumed 

 one poftulate and taken tzvoj and the latter of them is erro- 

 neous, namely, that all gafes are porous. It is true, I have 

 taken two poflulates into the argument, without exprefsly 

 requiring both ; the former being peculiar to my theory, was 

 necelTarlly demanded in a formal way ; the latter being the 

 refult of all experience, and never in any one inftance having 

 been found to fail, 1 thought it might tacitly be aflumed., 

 However, the judgment of philofopliers muft be fufpended on- 

 this head, as Mr. G. it feems, is about to prove that Jio gas 

 is porous, and that a cubic foot of one gas cannot be put into a. 

 "jejjel that is previoiijly occupied by another gas. Mr. G. furely 

 cannot be ferious in this objedlion ; but merely ufes it to gain 

 time, and means to turn it off with a laugh, that he has at 

 leaft produced one folid argument againft my airy hypo- 

 thefis. 



Mr. G. finds it extremely convenient for his purpofe, that 

 I fliould grant him the following poftulate : " If a particle of 

 vapour can pafs freely through the air, a fecond can alfo fuc- 

 ceed it at any given diftance." I certainly cannot concede 

 fo indefinite a demand ; but it will perhaps be of equal ufe to 

 him to have the following: If d be the diftance of two par* 

 tides of vapour of the temperature of 212°, and prefiure 30 

 ' inches ; then, at the temperature oF 60° or upwards, if one 



particle of vapour can pafs freely through the air, a fecond 

 may fucceed it at any diftance greater than 4 d. 

 i As for the important argument which I confider equivalent 



to a demonftration of the nature of vapour, and of its relaiion 

 \ to gafes, and entirely inimical to the notion of chemical affi- 



nity, Mr. G. has not ventured to revive it : Probably he has 

 fomething in referve on this head. I mean the argument de- 

 rived from the fad, that a vacuum, or any kind of air of 

 any denfity whatever, takes up juft the fame quantity of any 

 \ vapour. 



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