446 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



zELius, I believe, who considered the heat and light evolved in cases of combustion 

 as the consequences of this mode of exertion of the electric powers of the combining 

 particles. But it will require a much more exact and extensive knowledge of the 

 nature of electricity, and the manner in which it is associated with the atoms of 

 matter, before we can understand accurately the action of this power in thus causing 

 their union, or comprehend the nature of the great difference which it presents in the 

 two modes of action just distinguished. We may imagine, but such imaginations must 

 for the time be classed with the great mass of douhtful knowledge (876.) which we ought 

 rather to strive to diminish than to increase ; for the very extensive contradictions of 

 this knowledge of itself shows that but a small portion of it can ultimately prove true. 



960. Of the two modes of action in which chemical affinity is exerted, it is im- 

 portant to remark, that that which produces the electric current is as definite as that 

 which causes ordinaiy chemical combination ; so that in examining the production or 

 evolution of electricity in cases of combination or decomposition, it will be necessary, 

 not merely to observe certain effects dependent upon a current of electricity, but also 

 their quantity : and though it may often happen that the forces concerned in any par- 

 ticular case of chemical action may be partly exerted in one mode and partly in the 

 other, it is only those which are efficient in producing the current that have any rela- 

 tion to voltaic action. Thus, in the combination of oxygen and hydrogen to produce 

 water, electric powers to a most enormous amount are for the time active (861. 873.); 

 but any mode of examining the flame which they form during energetic combination, 

 which has as yet been devised, has given but the feeblest traces. These therefore may 

 not, cannot, be taken as evidences of the nature of the action ; but are merely inci- 

 dental results, incomparably small in relation to the forces concerned, and supplying 

 no information of the way in which the particles are active on each other, or in which 

 their forces are finally arranged. 



961. That such cases of chemical action produce no current of electricity, is per- 

 fectly consistent with what we know of the voltaic apparatus, in which it is essential 

 that one of the combining elements shall form part of, or be in direct relation with, 

 an electrolytic conductor (921. 923.). That such cases produce no fr^ee electricity of 

 tension, and that when they are converted into cases of voltaic action they produce a 

 current in which the opposite forces are so equal as to neutralize each other, prove 

 the equality of the forces in the opposed acting particles of matter, and therefore the 

 equality of electric power in those quantities of matter which are called electro- 

 chemical equivalents (824.). Hence another proof of the definite nature of electro- 

 chemical action (783. &c.), and that chemical affinity and electricity are forms of 

 the same power (917- &c.). 



962. The direct reference of the effects produced by the voltaic pile at the place of 

 experimental decomposition to the chemical affinities active at the place of excitation 

 (891. 917.), gives a very simple and natural view of the cause why the bodies or i(ms 

 evolved pass in certain directions ; for it is only when they pass in those directions 



