6N MIXED GASES. p 



law of their Specific gravities, as soon as their centres of gra- Examination of 

 vity are separated by introducing: into the space occupied by Mr. Dalton's 

 r. r u .-^ r A r. c .w u theory ef mix. 



C, a fresh quantity or A or B : m consequence or this altera- ^^ gases. 



^ion the centre of gravity of the heavier fluid will begin to de- 

 scend while that of the lighter moves upwards. When once 

 the centres of two gases are placed apart, their separation will 

 become permanent ; because, when at a distance, they are 

 urged in opposite directions by a force resulting from the dif- 

 ference of the specific weights of the two fluids; and this con- 

 trariety of efforts must continue so long as the two centres are 

 disjoined, consequently this opposition of force must be last- 

 ing ; seeing nothing can put an end to it but an union^ which 

 it will always prevent. Nor can the! mutual repulsion of the 

 constituent particles of each gas, considered apart, in any man- 

 ner promote the junction of the centres of gravity of the two 

 fluids ; because the action and reaction of a number of bodies 

 amongst themselves do not alter the state of their common 

 centre of gravity, whether it be at rest or in motion: so that 

 A and B are under the necessity of observing the law of their 

 specific gravities, just as if the kindred particles of each fluid 

 were actuated by no reciprocal repulsion nor any other cause 

 of reaction. The doctrine of gases, which are mutually ine- 

 lastic, is rendered indefensible by the preceding arguments ; 

 for the hypothesis is thereby exposed to a difficulty which the 

 author of the theory justly remarks, makes a mixture of mu- 

 tually repulsive gases of different specific gravities an impro- 

 bable conjecture; so that his own objection ultimately dis- 

 countenances the leading opinions of that theory vvhioh it in- 

 duced him to adopt in particular. At the same time, philoso- 

 phers are convinced that the atmosphere is a compound of 

 gases, possessing various degrees of specific weight ; they 

 moreover know, that different chemical agents perpetually dis- 

 turb the equilibrium of the compound, as some of them con- 

 stantly absorb while others unfold the gases of which it is com- 

 posed. The preceding facts are certain ; consequently the 

 heterogeneous elements of the atmosphere must be united by » 

 common tie, which may be denominated a species of afTinity, 

 at least while our knowledge of the subject remains in its pre- 

 sent imperfect state. The transparency of the great body of 

 air surrounding the earth, also aflfords a strong argument for 

 the chemical union of its componeat fluids; and, at the, same 



