affinity, and consequently the affinity for oxygen, must be an
electrical attraction. If zinc has an affinity for oxygen, it
must be because the zinc is either electropositive or
electronegative to oxygen. If it has a greater affinity for
oxygen than copper has, then the zinc must be either
electropositive or electronegative to copper. This being the
case, and both being conductors, it is not surprising that some
electricity will flow from one to the other when the two metals
are brought into contact.

Those writers who attribute the oxidation theory of contact
electrification to Fabroni apparently overlook the fact that
not oxidation, but the weakening of the cohesion of at least
one of the metals due to their contact, was the primary
phenomenon in Fabroni's theory. When this is remembered, it is
seen that the observations of Bennett and Fabroni, instead of
furnishing arguments for two conflicting theories, actually
serve, as all true scientific observations must, to supplement
each other.

Thus we now know that cohesion or affinity is an electrical
attraction between the atoms or molecules of a body. The only
known methods of changing the electrical attraction between two
bodies whose distances and directions from other bodies remain
constant is by varying the magnitude of their charges or by
changing the specific inductive capacity of the medium between
them. Bennett observed that when two pieces of different metal
in their normal electrical condition are placed in contact,
there is a redistribution of the charges of their surface
atoms. Fabroni observed under the same conditions a change in