434 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



of electrodes consisting- of matter, having more or less affinity for the elements evolved 

 from the decomposing electrolyte, various intermediate degrees may be obtained. 



915. Returning to the consideration of the source of electricity (878, &c.), there 

 is another proof of the most perfect kind that metallic contact has nothing to do 

 with the production of electricity in the voltaic circuit, and further, that electricity is 

 only another mode of the exertion of chemical forces. It is, the production of the 

 electric spark before any contact of metals is made, and by the exertion oi pure and 

 unmixed chemical forces. The experiment, which will be described further on (956.), 

 consists in obtaining the spark upon making contact between a plate of zinc and a 

 plate of copper plunged into dilute sulphuric acid. In order to make the arrange- 

 ment as elementary as possible, mercurial surfaces were dismissed, and the con- 

 tact made by a copper wire connected with Xh^ copper plate, and then brought to 

 touch a clean part of the zinc plate. The electric spark appeared, and it must of 

 necessity have existed and passed before the zinc and the copper were in contact, 



916. In order to render more distinct the principles which I have been endeavouring 

 to establish, I will restate them in their simplest form, according to my present belief. 

 The electricity of the voltaic pile (856. note) is not dependent either in its origin or 

 its continuance to the contact of the metals with each other (880. 915.). It is entirely 

 due to chemical action (882.), and is proportionate in its intensity to the intensity of 

 the affinities concerned in its production (908.) ; and in its quantity to the quantity of 

 matter which has been chemically active during its evolution (869.). This definite pro- 

 duction is again one of the strongest proofs that the electricity is of chemical origin. 



917. As volta-electro-generation is a case of mere chemical action, so volta-electro- 

 decomposition is simply a case of the preponderance of one set of chemical affinities 

 more powerful in their nature, over another set which are less powerful ; and if the 

 instance of two opposing sets of such forces (89 1 .) be considered, and their mutual re- 

 lation and dependence borne in mind, there appears no necessity for using, in respect 

 to such cases, any other term than chemical affinity, (though that of electricity may 

 be very convenient,) or supposing any new agent to be concerned in producing the 

 results; for we may consider that the powers at the two places of action are in direct 

 communion and balanced against each other through the medium of the metals (891.), 

 fig. 4, in a manner analogous to that in which mechanical forces are balanced against 

 each other by the intervention of the lever (1031.). 



918. All the facts show us that that power commonly called chemical affinity, can 

 be communicated to a distance through the metals and certain forms of carbon ; that 

 the electric current is only another form of the forces of chemical affinity ; that its 

 power is in proportion to the chemical affinities producing it ; that when it is deficient 

 in force it may be helped by calling in chemical aid, the want in the former being 

 made up by an equivalent of the latter ; that, in other words, the forces termed che- 

 mical affinity and electricity are one and the same. 



