of the Elements of Atmospheric Air, x 8T 



&ncy, as in an atmosphere of pure oxygen of common den- 

 sity. At any rate, it is notorious that, as the density of 

 common air is increased., combustion in it becomes more 

 vigorous. Though I have never attempted combustion in an 

 atmosphere of pure oxygen of £th the common density, I 

 can scarcely doubt that the appearances would be much Uig 

 same as in open air. It is probable, then, that the facts 

 under this head, if duly investigated, would turn out in 

 favour of the hypothesis of air being a mixture. 



4. (C A gas, no way distinguishable from common air, 

 frequently makes its appearance during the preparation of 

 nitric acid 3 and Mr. Davy decomposed nitrous oxide by 

 passing it through a red-hot tube, and converted it into nitric 

 acid and a gas which possessed the properties of common 

 air. Now, if air were a mere mixture, it is infinitely impro- 

 bable that its two constituent parts should be evolved du- 

 ring such processes exactly in the proportion that exists in 

 common air." Granted : but as the force of this argument 

 rests upon the exact proportion of oxygen and azpt in the 

 gases so evolved, that is, upon their being constituted al- 

 ways of 21 per cent, oxygen and 79 azot, the facts should 

 be made out accordingly. Dr. Priestley is the only one I 

 know of who has particularly examined the gas produced 

 in the preparation of nitric acid; and he found it to have 

 much more oxygen than common air. Mr. Davy, in his 

 analysis of nitrous oxide, found the gas analogous to atmo- 

 spheric air always to contain less oxygen, though it was 

 nearly of the atmospheric standard. 



The quick ascent of hydrogen, and the descent of carbonic 

 acid, have been objected to my hypothesis, as facts that 

 prove the operation of the laws of specific gravities on clas- 

 tic fluids. No doubt can exist that a portion of elastic fluid 

 completely insulated, as a balloon, or bubble of carbonic 

 acid or hydrogen surrounded by a film of water, is subject 

 to the laws of gravitation, and rises or falls in elastic fluids 

 on the same principle as it rises in water : the same must be 

 allowed whenever a vessel containing a considerable portion 

 of elastic, fluid is suddenly exposed at some surface to the 

 atmosphere : in this case the fluids must operate upon each 

 other for a few moments in a collected capacity, as in elastic 

 bodies; because' the diffusive or repulsive force, by which 

 they constantly tend to dispersion, is comparatively slow 

 in producing the ultimate effect, being in this respect ex- 

 actly similar to chemical affinity, the operation gradually di- 

 minishing as the effect draws towards a conclusion. No- 

 No. 73, June 1804, F thing 



