FRANKLIN
1706-1790
In
1776 Benjamin Franklin helped draft the Declaration of Independence
and soon after set sail for Paris, sent by the Continental Congress to
negotiate a treaty with the French. He was welcomed with great enthusiasm,
for his fame had preceded him—fame not as a statesman but as a scientist.
He was already one of the eight foreign associates of the French Academy
of Sciences (a century would pass before another American got this rare
honor). As the "Newton of electricity" whose theories, experiments
and lightning rods were known the length of Europe, Franklin was given
a respectful hearing. Deliberately simple in dress and manner, sparkling
with wit and homely wisdom, Franklin quickly convinced his audience that
he—and by extension the newborn United States of America—embodied
unspoiled virtue. He became perhaps the chief factor in winning the support
of the French government and its fleet, support which proved decisive
in the War for Independence. If Franklin the diplomat could achieve so
much, it was largely because first he was Franklin the scientist.
He was forty years old before he took up scientific research; until then
he had been chiefly concerned with earning a living. His brief formal
education ended at the age of ten when he was removed from school to help
his father, a Boston chandler
and soapmaker. But he had acquired an interest in books and was soon apprenticed
to his elder brother, a printer. Before the end of his apprenticeship
he ran away to seek his fortune, and after a short time in Philadelphia,
sailed for England. In London he perfected his knowledge of the art of
printing and made friends with some gentlemen scientists. He just missed
being introduced to the aging Isaac Newton. Returning to Philadelphia
in 1726, Franklin set up a printing business. His Poor Richard's Almanack
and other publications were popular, and he also succeeded in colonial
society, throwing himself enthusiastically into every variety of civic
affairs.
In 1743 an itinerant lecturer from England demonstrated the latest electrical
experiments to the wondering colonials. Franklin saw these demonstrations
and later bought the lecturer's entire apparatus. In 1745 he began to
experiment on his own, and soon after turned the management of his printing
business over to a partner. "When I disengaged myself . . . from
private business," he wrote, "I flatter'd myself that, by the
sufficient tho' modest fortune I had acquired, I had secured leisure during
the rest of my life for philosophical studies and amusements."
Experimental "philosophy" and parlor "amusements"
were not far apart in the 1740's. The phenomena of electricity in particular
seemed of minor importance; often they were studied out of simple fascination
with the curious toys and perplexing contradictions that made up the bulk
of the subject. Franklin, too, invented such tricks: see the queer game
of "treason" and the electrical barbecue in Letter IV, below.
But he also sought the principles behind the games. Aided by Philadelphia
friends, but using chiefly his own skilled hands and ingenious brain,
he devised simple—sometimes overly simple—explanations for the
bewildering variety of electrical phenomena. (During the same period he
also served on the Philadelphia city council and the Pennsylvania assembly,
and was much occupied with the problem of defending the colony from hostile
Indians and privateers.)
Electricity, said Franklin, is a substance which is conserved, and which
may be either "positive" (in excess) or "negative"
(deficient) in a body. The electrical fluid or "fire" repels
itself and is attracted to the substratum of "common matter."
Franklin also held that the common matter attracts itself; it was left
to one of his admirers, Franz AEpinus, to show that Franklin's principles
required that common matter repels itself. Despite its flaws, the "Franklinist"
theory explained electrical phenomena far better than any previous one,
and after improvement by AEpinus and others it drove its rivals from the
field throughout Europe.
Franklin meanwhile proposed an experiment which would prove at the same
time two exciting conjectures: that electricity is a powerful and universal
force of nature, and that this force can be controlled. He suggested that
a sharp point might "draw" electricity from a thundercloud,
just as a grounded point will discharge a nearby charged object in the
laboratory. This "Philadelphia experiment" was first tried in
France with a tall pointed rod; it worked, making Franklin famous as the
man who showed how to steal sparks from the lightning. A little later
and independently he tried the experiment himself, using a kite instead
of a tall rod (a dangerous activity, which later killed another experimenter).
While his electrical work was his greatest scientific achievement, Franklin
also contributed to knowledge of heat conduction, storms, the Gulf Stream,
etc., and invented bifocal glasses, the rocking chair, daylight saving
time, and more. He might have done more still, but after he had been working
for only a few years on electricity, his country called him to other tasks.
He put aside his researches reluctantly and even into his old age kept
hoping to return to them.
Franklin's discoveries were reported in his letters to his English friend
Peter Collinson and were published in London in a book, from which the
selections below are drawn. The results in Letter IV may seem commonplace
to a modern physicist where they are not simply confused, but in fact
most of this communication was new, startling and highly significant.
A few words of explanation may help. The letter deals with a Leyden jar
or phial filled with water connected to a terminal or hook
and coated with conducting foil connected to a wire or tail. Also
used are electrics, which we would now call dielectrics, such as
glass or wax; a non-electric is a conductor. The letter contains
the first statement of the Law of Conservation of Charge, the first useful
theory of the action of a condenser, and much else. We also give an excerpt
reporting the kite experiment.
More about Franklin in his 2006
Tercentenary site
