270 O^ MIXED GASES, 



Obfervations on The fum is fo near 100, that Mr. G. will not venture to pre- 

 Mr. Cough's fume any thing on the difference, further than that the data 

 gjfg5^ are ftill in a fmall degree incorrc6t, which I believe no body 



will difpute with him. 



Mr. G. by this time is ready to query, How do you know 

 your data to be more correct than mine? I will now inform 

 him. 



Dr. Prieftley was perhaps ihe firft to inveftigate the fpecific 

 gravities of the two gafes in queftion. His method was very 

 exceptionable; but fuch is generally the cafe in the infancy 

 of any fcience. (Sec Vol, IL Page 452, abridg. Ed. of his 

 JS'cit. Philof.) He found azotic gas as much lighter than 

 common air as oxigenous was heavier, Mr. Kirwan foon 

 after gave a much nearer approximation; namely, the one 

 which Mr. G. has adopted. Lavoifier alfo found the fpecific 

 gravity of feveral gafes. (See Elements of Cheviijiry, Append, 

 Table 7). His refults nearly agree with Kirwan*s in regard 

 to oxigen, but differ confiderably in regard to azote. Laftly, 

 Mr. Davy, when invefHgating the compounds of azote and 

 oxigen, found it expedient to afcertain with precifion the 

 fpecific gravity of the two gafes. Having every means of 

 his predeceffors, and their refults before him, he ought at 

 leaft to have decided in regard to the difference between 

 them. Accordingly he finds his refults to agree with Lavoi- 

 lier's in refpe6l to azote; but he finds the fpecific gravity of 

 oxigen fomewhat greater than either of them. (See Re- 

 fearches, pag. 565). 



The following table exhibits the refults of all thefe together, 

 reduced to the ftandard of atmofpheric air. 



Specific Gravities of 



Azotic Gas. Atmof. Air. Oxigenous Gas. 



According to Prieftley, .989 — 1. 000 — 1.01 1 



Kirwan, .985 ■— 1. 000 — 1.103 



Lavoifier, .966 — 1.000 — 1.102 



Davy, .966 — 1.000 — 1.127 



As for Mr. G.'s third datum, I think it fcarcely pardonable in 

 the prefent day, for any one to pretend to difcufs a queftion 

 concerning the conftitution of the atmofphere, under the un- 

 certainty whether it contains 22 or 28 per cent, of oxigen. 

 He ought to be acquainted with the hiitory of eudiometry, 



and 



