IMPROBABLE NATURE OF THE CONTACT FORCE. 
125 
phenomena we take two substances, as oxygen and hydrogen, we may conceive that 
two particles, one of each, being placed together and heat applied, they induce con- 
trary states in their opposed surfaces, according, perhaps, to the view of Berzelius 
(1739.), and that these states becoming more and more exalted end at last in a 
mutual discharge of the forces, the particles being ultimately found combined, and 
unable to repeat the effect. Whilst they are under induction and before the final 
action comes on, they cannot spontaneously lose that state ; but by removing the 
cause of the increased inductive effect, namely the heat, the effect itself can be 
lowered to its first condition. If the acting particles are involved in the constitution 
of an electrolyte, then they can produce current force ( 921 . 924 .) proportionate to 
the amount of chemical force consumed (868.). 
2069 . But the contact theory, which is obliged, according to the facts, to admit 
that the acting particles are not changed ( 1802 . 2067 .) (for otherwise it would be the 
chemical theory), is constrained to admit also, that the force which is able to make 
two particles assume a certain state in respect to each other, is unable to make them 
retain that state ; and so it virtually denies the great principle in natural philosophy, 
that cause and effect are equal ( 2071 .)- If a particle of platinum by contact with 
a particle of zinc willingly gives of its own electricity to the zinc, because this by its 
presence tends to make the platinum assume a negative state, why should the particle 
of platinum take electricity from any other particle of platinum behind it, since that 
would only tend to destroy the very state which the zinc has just forced it into ? 
Such is not the case in common induction ; (and Marianini admits that the effect 
of contact may take place through air and measurable distances* ;) for there a ball 
rendered negative by induction, will not take electricity from surrounding bodies, 
however thoroughly we may uninsulate it ; and if we force electricity into it, it will, as 
it were, be spurned back again with a power equivalent to that of the inducing body. 
2070 . Or if it be supposed rather, that the zinc particle, by its inductive action, 
tends to make the platinum particle positive, and the latter, being in connection with 
the earth by other platinum particles, calls upon them for electricity, and so acquires 
a positive state; why should it discharge that state to the zinc, the very substance, 
which, making the platinum assume that condition, ought of course to be able to 
sustain it? Or again, if the zinc tends to make the platinum particle positive, why 
should not electricity go to the platinum from the zinc, which is as much in contact 
with it as its neighbouring platinum particles are? Or if the zinc particle in contact 
with the platinum tends to become positive, why does not electricity flow to it from 
the zinc particles behind, as well as from the platinum'|~? There is no sufficient pro- 
* Memorie della Societa Italiana in Modena, 1837, xxi. 232, 233, &c. 
t I 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. 
