1 72 MEMOIR OF DR. DALTON, AND 



to suspect that the proportions of the principles are not the 

 same in every specimen ot the elastic fluid which we consider 

 as fixable air. When the dense inflammable air first expelled 

 from charcoal was used, the result was nearly the same. And 

 from the whole, I conclude, that when as much inflammable 

 air of this kind is employed, as can be converted in the 

 explosion, by the empyreal air, the fixable air consists of one 

 part by weight of the acid matter of acetous acid or charcoal, 

 and nearly, or accurately, two pSrts of empyreal air; and 

 almost one-fifth of this kind of inflammable air is phlogiston, 

 and the remainder mere acid basis of fixable air, and of acetous 

 acid, charcoal, oils, spirits, and of all substances that yield 

 acetous acid or dense inflammable air abundantly."* ♦ 



The same remarks apply to this. The " nearly" two parts 

 are just as probable, in his mind, as the "accurately" two 

 parts, which would not have been the case had he found any 

 defining law to express on the subject. 



Then he says, further on,t " It seems, therefore, that the 

 proportions in which the acid and phlogistic matter are com- 

 bined, in different specimens of inflammable air expelled from 

 vegetable substances, do vary considerably," &c. This refers 

 to his tables of results. 



He believes that the particles of the different gases unite to 

 form molecules of compound gases, page 317: "I consider 

 the specific gravity as a safe guide in our investigation of 

 these affinities and of their order, in regard only to the elastic 

 fluids which seem to consist of no more than one kind of 

 gravitating matter engaged in the repellent atmospheres ; and 

 of fixed air, dense inflammable air, acid air, the phlogistic 

 alkaline air, and others, I would observe, that the atmospheres 

 include molecules, instead of solitary ultimate parts; for, 

 without this chemical union of heterogeneal parts, and the 

 formation of molecules, an elastic fluid of the kind that I now 

 speak of could not differ, as it does, from either kind of matter 



•Page 291. j Page 394. 



