68 



DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



ing in the solid, the liquid, and the gaseous state ; but when we speak of the gaseous 

 state as being due to the mutual repulsions of the particles or of their atmospheres, 

 although we may err in imagining each particle to be a little nucleus to an atmosphere 

 of heat, or electricity, or any other agent, we are still not likely to be in error in con- 

 sidering the elasticity as dependent on mutuality of action. Now this mutual relation 

 fails altogether on the side of the gaseous particles next to the platina, and we might 

 be led to expect a priori a deficiency of elastic force there to at least one half ; for if, 

 as Dalton has shown, the elastic force of the particles of one gas cannot act against 

 the elastic force of tlie particles of another, the two being as vacua to each other, so 

 is it far less likely that the particles of the platina can exert any influence on those of 

 the gas against it, such as would be exerted by gaseous particles of its own kind. 



627. But the diminution of power to one half on the side of the gaseous body 

 towards the metal is only a slight result of what seems to me to flow as a necessary 

 consequence of the known constitution of gases. An atmosphere of one gas or vapour, 

 however dense or compressed, is in effect as a vacuum to another : thus, if a little 

 water were put into a vessel containing a dry gas, as air, of the pressure of one hundred 

 atmospheres, as much vapour of the water would rise as if it were in a perfect vacuum. 

 Here the particles of watery vapour appear to have no difficulty in approaching within 

 any distance of the particles of air, being influenced solely by relation to particles of 

 their own kind ; and if it be so with respect to a body having the same elastic powers 

 as itself, how much more surely must it be so with particles, like those of the platina, 

 or other limiting body, which, at the same time that they have not these elastic 

 powers, are also unlike it in nature. Hence it would seem to result that the particles 

 of hydrogen or any other gas or vapour which are next to the platina, &c., must be in 

 such contact with it as if they were in the liquid state, and therefore almost infinitely 

 closer to it than they are to each other, even though the metal be supposed to exert 

 no attractive influence over them. 



628. A third and very important consideration in favour of the mutual action of 

 gases under these circumstances is their perfect miscibility. If fluid bodies capable of 

 combining together are also capable of mixture, they do combine when they are mingled, 

 not waiting for any other determining circumstance ; but if two such gases as oxygen 

 and hydrogen are put together, though they are elements having such powerful affinity 

 as to unite naturally under a thousand different cirpumstances, they do not combine 

 by mere mixture. Still it is evident that, from their perfect association, the particles 

 are in the most favourable state possible for combination, upon the supervention of 

 any determining cause, such either as the negative action of the platina in suppressing 

 or annihilating, as it were, their elasticity on its side ; or the positive action of the 

 metal in condensing them against its surface by an attractive force ; or the influence 

 of both together. 



629. Although there are not many distinct cases of combination under the influ- 

 ence of forces external to the combining particles, yet there are sufficient to remove 



