On the 'llieonj vf mixed Gascj. lOg 



the necessity of observing the law of their specific gravities, 

 just as if the kindred particles of each fluid were actuaied by 

 no reciprocal repulsion nor any other cause of re-action. 

 The doctrine of gases, which are mutually inelastic, is ren- 

 dered indefensible by the preceding arguments ; for the hy- 

 pothesis is thereby exposed to a diiriculty which, the author 

 of the theory justly remarks, makes a mixture of mutuallv 

 repulsive gases of difierent specific gravities an improbable 

 conjecture; so that his own objection ultimately discounte- 

 nances the leading opinions of that theory which it induced 

 him to adopt in particular. At the same time philosophers 

 are convinced that the atmosphere is a compound of gases 

 possessing various degrees of specific weight ; they moreover 

 know that different chemical agents perpetually disturb the 

 equilibrium of the compound, as some of them constantly 

 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 a common tic, which may be denominated a species of 

 affinity, at least while our knowledge of the subject remains 

 in its present imperfect state. The transparency of the great 

 body of air surrounding the earth, also affords a strong argu-. 

 ment for the chemical union of its component fluids, and 

 at the same time discountenances the idea of the compound 

 being a mechanical mixture of any description whatever ; 

 for when a number of diaphanous bodies of different specific 

 gravities are mixed together, they form an aggregate which 

 is opaque; but the union of the substances by fusion renders 

 the mass transparent in many instances. Now, as the at- 

 mosphere is diaphanous, we are obliged, bv the principles 

 of sound argument, to consider it in the light of a com- 

 pound, the ingredients of which are united by a chemical 

 tie. Whatever may he the condition of the elastic fluids 

 which enter into the composition of common air, one thing 

 is certain, from a preceding paragraph of this essay, namelv, 

 no one of them can ujaintaln a separate equilibrium as long 

 as it makes an individual of the aggregate ; consequentlv 

 eich particle of the compound must be urged by a force rc- 



SuitlHi' 



