292 Roj/ul Society. 



Thenard. In discussing the theory of these remarkable effects, the 

 author advances some new views of the conditions of elasticity at the 

 exterior of a mass of gaseous matter confined by solid surfaces. The 

 elasticity of gases he considers as being dependent on the mutual ac- 

 tion of the particles, especially of those which are contiguous to each 

 other; but this reciprocity of condition is wanting on the sides of the 

 exterior particles which are next to the solid substance. Then, rea- 

 soning on the principle established by Dalton, that the particles of 

 different gases are indifferent to one another, so that those of one gas 

 may come within almost any distance of those of another gas, what- 

 ever mav be the respective degrees of tension in each gas among the 

 particles of its own kind, he concludes that the particles of a gas, or 

 of a mixture of gases, which are next to the platina, or other solid body 

 not of their own chemical nature, touch that surface by a contact as 

 close as that bv which the particles of a solid or liquid body touch 

 each other. This proximity, together with the absence of any mutual 

 relation of the gaseous particles to particles of their own kind, combined 

 also with the direct attractive force exerted by the platina, or other 

 solid body, on the particles of the gases, is sufficient, in the opinion 

 of the author, to supply what is wanting in order to render effective 

 the affinity between the particles of oxygen and hydrogen ; being, in 

 fact, equivalent to an increase of temperature, to solution, or to any 

 of the other circumstances which are known to be capable of adding 

 to the force of the affinities inherent in the substances themselves. 



Some very curious cases of interference with this action of platina 

 and other mttals are next described. Thus, small quantities of car- 

 bonic oxide, or olefiant gas, mixed with the oxygen and hydrogen 

 gases, totally prevent the effect in question ; while very large quan- 

 tities of carbonic acid, or nitrous oxide gas, do not prevent it: and 

 it is remarkable, that the former of these gases do not affect the me- 

 tallic plates permanently; for it the plates be removed from those 

 mixtures, and put into pure oxygen and hydrogen gases, the combi- 

 nation of these elements takes place. 



The author concludes by some general notice of numerous cases 

 of physical action, which show the influence of certain modifications 

 of the conditions of elasticity at the external surface of gaseous 

 bodies. 



The seventh series, which is a continuation of the subject of the fifth, 

 namely, electro-chemical decomposition*, commences with a prelimi- 

 nary exposition of the reasons which have induced the author to intro- 

 duce into this department of science several new terms, which appear 

 to be required in order to avoid errors and inaccuracies in the state- 

 ment both of facts and theories. As a substitute for the term pole, 

 and with a view to express also a part of the voltaic apparatus to 

 which that name has never been applied, although it be identical with 

 a pole in its relation to the current, the author proposes to employ 

 the term electrode. The surfaces of the decomposing body, at which 

 the positive current of electricity enters and passes out, are denomi- 

 nated respectively the e'mode and the exnde. Bodies which are de- 



* An abstract of Mr. Faraday's Fifth Series of Experimental Researches 

 in Electricity will be found in Loud, and Edinb. Phil. Mag. vol. hi. p. 4fi0 



