(5 ON MIXED gases/ 



r ,^- ,.-nn «f Let the fiorure P M I N K V, Plate I, Fig. 2, represent 

 Examination ot o » ^ t> ' r 



Mr. Dalton's this space, in which xVI V N K is the given plane. — Now since 

 theory of mix- every point of this plane may be suppo-.ed to be at an equal 

 distance from the earth's centre, the density of every homoge- 

 neous gas supported by it, will be the same in all parts of it. 

 Let the constituent fluids be denominated A and B ; also let C 

 denote the compound ; moreover let the densities of A and B, 

 at P, bep and q ; let P X and X Y be two equal evanescent 

 parts of the line P V. Now seeing the pressure acting upon 

 an elastic fluid is as the density of it, the fluxionarie increments 

 of/) and q, are as these quantities; but the densities of A and 

 B, in the point X, are equal to the sums of p and q united to 

 their increments respectively ; let these sums be called e and 

 /; then e is to/ asp is to q, by composition of proportion : in 

 Jike manner we find the density of A at Y to be to that of B at 

 the same point as e is to/; i. e, as p is to q; thence it follows 

 that the fluxionary increments of the two densities have uni- 

 versally theglvin ratio of p to q ; consequently the contempo- 

 rary fluents, or the densities themselves have the same given 

 ratio : now what has been proved of the two gases A and B may 

 be extended to any othej number; viz. the ratios of their 

 densities, on the same horizontal plane W'iil be given, 

 , The ratio of A B> &c, being found to be constant, we can 

 proceed to investigate the proportions of the quantities of mat- 

 ter contained in these fluids. Let D and d be the densities of 

 A and B, in the plane MKN V ; also let W and w be the quan- 

 tities of matter of each kind, contained in the variable space 

 PMKNV; call PV x, and the area of the plane MKNVj/: 

 now the fluxion of the space PMKNV is exprssed hy y into, 

 the fluxion of x\ moreover, the quantities of matter in two 

 solids are in the complicate ratios of their magnitudes and den- 

 sities,' or in that of their densi.ties only, if their magnitudes be 

 equal; therefore the fluxion ofW is to that of tc as D is to d; 

 because, the fluxionary magnitude is common both to W and 

 w, but D is to cf as p to 9-, a constant ratio; con :!equently 

 fluxion of W is to fluxion of re as p is to ^; therefore W has to 

 n^ the same given ratio ; that is, the matter in A i^ to the mat- 

 ter in B as p. is to q. \n the next place, let R and r be the 

 distances of the centres of gravity of A and B, from the point 

 P, taken in the line PI : then R into the fluxion of W is. equal 

 to the product of D, Y, x, and the fluxion of ;ir, from a v/eli 



