124 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVII.) 
metals are not far apart in the thermo series : nor should it be nearly alike to pla- 
tinum and gold voltaically, since they are far apart in the thermo series. 
2062. Finally, in the thermo circuit there is that relation to heat which shows that 
for every portion of electric force evolved, there is a corresponding change in another 
force, or form of force, namely heat, able to account for it ; this the united experi- 
ments of Seebeck and Peltier have shown. But contact force is a force which has 
to produce something from nothing, a result of the contact theory which can be better 
stated a little further on (2069. 2071. 20/3.). 
2063. What evidence then for mere contact excitement, derivable from the facts of 
thermo electricity, remains, since the power must thus be referred to the acid or other 
electrolyte used (2060.) and made, not only to vary uncertainly for each metal, but 
to vary also in direct conformity with the variation of chemical action (1874. 1956. 
1992. 2006. 2014.). 
2064. The contact theorist seems to consider that the advocate of the chemical 
theory is called upon to account for the phenomena of thermo-electricity. I cannot 
perceive that Seebeck’s circle has any relation to the voltaic pile, and think that the 
researches of Becquerel* are quite sufficient to authorize that conclusion. 
% x. Improbable nature of the assumed contact force. 
2065. I have thus given a certain body of experimental evidence and consequent 
conclusions, which seem to me fitted to assist in the elucidation of the disputed point, 
in addition to the statements and arguments of the great men who have already 
advanced their results and opinions in favour of the chemical theory of excitement in 
the voltaic pile, and against that of contact. I will conclude by adducing a further 
argument founded upon the, to me, unphilosophical nature of the force to which 
the phenomena are, by the contact theory, referred. 
2066. It is assumed by the theory (1802.) that where two dissimilar metals (or 
rather bodies) touch, the dissimilar particles act on each other, and induce opposite 
states. I do not deny this, but on the contrary think, that in many cases such an 
effect takes place between contiguous particles ; as for instance, preparatory to action 
in common chemical phenomena, and also preparatory to that act of chemical com- 
bination which, in the voltaic circuit, causes the current (1738. 1743.). 
2067- But the contact theory assumes that these particles, which have thus by their 
mutual action acquired opposite electrical states, can discharge these states one to 
the other, and yet remain in the state they were first in, being in every point entirely 
unchanged by what has previously taken place. It assumes also that the particles, 
being by their mutual action rendered plus and minus, can, whilst under this induc- 
tive action, discharge to particles of like matter with themselves and so produce a 
current. 
2068. This is in no respect consistent with known actions. If in relation to chemical 
* Annales de Chimie, 1829, xli. 355. xlvi. 275. 
