1 |t Illustration of the Theory of 



the doctrine was opposed by almost every member interested 

 in such subjects, and by no one more strenuously than 

 myself. Subsequent attention, however, to the evidences 

 of the theory, and, still more, the results of experiments, 

 which were made under impressions very unfavourable to the 

 hypothesis, have satisfied me that the opposition to it arose 

 chiefly from an imperfect comprehension of the argument; 

 and that your theory is far better adapted than any former 

 one for explaining the relation of mixed gases to each 

 other, and especially the connection between gases and 

 water. 



The distinguishing principle of your doctrine, I appre- 

 hend to be, that mixed gases neither attract nor repel each 

 other, and that every gas is as a vacuum to every other gas. 

 It is not my intention to recapitulate your proofs of this po- 

 sition, but merely to add to them the evidence of a few facts 

 which have occurred to me, and which strongly tend to 

 establish the same conclusion. 



From a series of experiments, which I communicated to 

 the Royal Society, and which appeared in their Transactions 

 for 1803, it may, I think, be safely inferred, that the rela- 

 tion of gases to water is altogether a mechanical one ; for 

 the quantity absorbed follows exactly the ratio of the pres- 

 sure. If then it can be shown that a gas, absorbed by 

 water, is not retained in its place by an atmosphere of any 

 other gas, we shall be furnished with a strong presump- 

 tion, that different gases do not gravitate on each other. 



It is well known that water may be charged with its own 

 bulk, or rather more, of carbonic acid gas under a pressure 

 of 30 inches of mercury. The gas, thus absorbed, is re- 

 tained so long as the water is preserved from contact with 

 any other gas ; but, when exposed to the atmosphere, the car- 

 bonic acid gas rapidly escapes. Now this effect can be only 

 ascribed to one of two causes : 1st, The affinity of carbonic 

 acid for atmospheric, air may surpass that of its affinity for 

 water ; or, 2dly, The air of the atmosphere does not press 

 on the gas in the water, which is therefore placed under 

 similar circumstances, as if exposed under the exhausted 

 receiver of an air pump. 



Were the first explanation the true one, it might be ex- 

 pected, that equal quantities of various gases w(Tuld detach 

 different quantities of carbonic acid from like volumes of 

 impregnated water ; because the affinities of these gases, as 

 in all other cases of chemical affinity, differing in force, 

 would occasion their combining with different quantities of 

 carbonic acid, and in a certain order. But in making the 



experiment, 



