Benjamin Franklin's travels and correspondence brought him into contact with some of the best scientific minds in Europe, and his own imagination was caught by the popular studies of electricity that had become fashionable in the 1740's. Although Franklin had never had any scientific training at all, he started experiments to investigate electrical phenomena with such skill and insight that he was soon recognized and respected as a scientist.
Franklin proposed that electricity was an
"element diffused among and attracted by other
matter." He identified two kinds of electricity --
one that was possessed by a body "undercharged with
electrical fire" and another by a body
"overcharged." Replacing the words
"electrical fire" with the word
"electrons" gives us the modern description of
positive and negative charge.
Franklin went on to propose that when an "overcharged" body approached an "undercharged" one, an electrical spark leaped between them, equalizing the amount of "electrical fire" in the two bodies. This would prove to be the first accurate description of the mechanism by which electrons pass between bodies of differing electrical potential.
Franklin's best-known discovery, however, was
that lightning is caused by discharges of static
electricity in the atmosphere. He made this discovery by
fixing a metal key to a kite by a conducting thread of
silk and flying it in a lightning storm. In effect,
Franklin was diverting some of the electrical energy of
the lightning through the key and into the earth. In the
months following publication of his findings, several
scientists in Europe were electrocuted trying to repeat
the experiment. (Despite all the popular depictions of
Franklin's experiments, there is absolutely no evidence
that he was actually foolish enough to either hold onto
the string or to touch the key during his experiment; the
discharge of electricity would have been just as visible
if the key was tied to the string as close to the ground
as possible. Unfortunately, not every scientist who
attempted to replicate Franklin's experiment was as
practical as Franklin.)
The immediate practical result of Franklin's experiment was a design for the first lightning conductor. He suggested that pointed metal rods be placed on the roofs of houses and connected to the earth to divert lightning away from the structure of the houses, dissipating the energy harmlessly in the ground.
Questions or comments about this page?
Feldman, Anthony and Peter Ford. Scientists and
Inventors, The People Who Made Technology from Earliest
Times to Present Day. New York:Facts on File, 1979
(pp. 52-53).
The Robinson Library
Science.--Physics.--Electricity and Magnetism.--History.
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