Theories of the Voltaic Battery. 479 
the zinc, the very substance, which, making the platinum as- 
sume that condition, ought of course to be able to sustain it? 
Or again, if the zinc tends to make the platinum particle po- 
sitive, why should not electricity go to the platinum from the 
sine, which is as much in contact with it as its neighbouring 
platinum particles are? Or if the zine particle in contact 
with the platinum tends to become positive, why does not 
electricity flow to it from the zine particles behind, as well as 
from the platinum*? There is no sufficient probable or phi- 
losophic cause assigned for the assumed action; or reason 
given why one or other of the consequent effects above men- 
tioned should not take place: and, as I have again and again 
said, I do not know of a single fact, or case of contact current, 
on which, in the absence of such probable cause, the theory 
can rest. 
2071. The contact theory assumes, in fact, that a force which 
is able to overcome powerful resistance, as for instance that of 
the conductors, good or bad, through which the current passes, 
and that again of the electrolytic action where bodies are de- 
composed by it, can arise out of nothing; that, without any 
change in the acting matter or the consumption of any gene- 
rating force, a current can be produced which shall go on for 
ever against a constant resistance, or only be stopped, as in 
the voltaic trough, by the ruins which its exertion has heaped 
up in its own course. ‘This would indeed be a@ creation of 
power, and is like no other force in nature. We have many 
processes by which the form of the power may be so changed 
that an apparent conversion of one into another takes place. 
So we can change chemical force into the electric current, or 
the current into chemical force. The beautiful experiments 
of Seebeck and Peltier show the convertibility of heat and 
electricity; and others by Cirsted and myself show the con- 
vertibility of electricity and magnetism. But in no cases, not 
even those of the Gymnotus and Torpedo (1790.), is there a 
pure creation of force; a production of power without a cor- 
responding exhaustion of something to supply it+. 
* T have spoken, for simplicity of expression, as if one metal were active 
and the other passive in bringing about these induced states, and not, as 
the theory implies, as if each were mutually subject to the other. But this 
makes no difference in the force of the argument ; whilst an endeavour to 
state fully the joint changes on both sides, would rather have obscured 
the objections which arise, and which yet are equally strong in either view. 
+ (Note, March 29, 1840).—I regret that I was not before aware of most 
important evidence for this philosophical argument, consisting of the opi- 
nion of Dr. Roget, given in his Treatise on Galvanism in the Library of 
Useful Knowledge, the date of which is January 1829. Dr. Roget is, upon 
the facts of the science, a supporter of the chemical theory of excitation ; 
