Unit 2: Those Inventive Americans!
Era 3: Revolution and the New Nation
- Benjamin Franklin's keen interest in improving
the world around him and his natural curiosity for the
way things worked are evident in his inventions. Franklin
is credited with inventing bifocals, the Franklin stove,
the glass harmonica, the lightning rod, and the odometer.
Choose two of these inventions and write a brief report
addressing the following: Why did Franklin invent it?
How did it work? Is it still in use today? Illustrations
of these inventions can be seen at the Franklin Institute
Science Museum Web site (http://www.fi.edu/franklin/inventor/inventor.html).
[Standard 4historical research capabilities]
Bifocals: Franklin was both nearsighted and
farsighted, and had to alternate between two pairs of
glasses depending on what he was trying to see. As a
solution to his frustrating problem, Franklin had the
lenses from his two pairs of glasses cut in half and
reassembled in one frame with the lenses for distance
on top and the lenses for reading on the bottom. Franklin's
idea for bifocals is still the basic model used today.
Franklin stove: Most homes in colonial America
were heated by fires in open fireplaces. Fireplaces
were inefficient heat sources because of the large amount
of wood needed and were dangerous because sparks could
easily ignite a fire elsewhere in the house. Franklin
invented an iron furnace stove that used less wood,
radiated more warmth through the heated iron, and was
safer because the fire was better contained. Franklin
stoves are still in use in some homes today.
Glass harmonica: While Franklin was traveling
in Europe, he witnessed an amateur musician play on
a set of "singing glasses," producing clear,
ringing sounds by rubbing a moistened finger on the
rims of wine glasses filled with varying levels of water.
Intrigued, Franklin worked to create an instrument that
incorporated the elements of the singing glasses. He
selected different-sized wine glasses, removed the stems,
drilled holes in the bottoms of the glasses, and corked
the holes. The glasses were arranged in order of increasing
size on a horizontal spindle, which could be rotated
by a foot treadle. Musicians played the glass harmonica
by touching moistened fingers to the edges of the glasses
while rotating them with the pedal. The glass harmonica
fell out of favor in the mid-nineteenth century, but
is currently making a comeback because of the efforts
of a German glassblower.
Lightning rod: Franklin's investigations into
the nature of electricity led him to this simple invention
with a powerful purpose. By mounting a pointed iron
rod on the highest point of a building, Franklin discovered
that it would attract lightning flashes and channel
the electrical current to the ground, thereby preventing
other parts of the building from catching on fire. Lightning
rods can be found on buildings today, although they
are usually made of copper.
Odometer: While serving as postmaster for
the northern colonies, Franklin had to establish mail
routes. In order to measure distances, he invented an
odometer, which could be attached to the axle of his
carriage wheels to count the rotations. Odometers are
standard instruments in modern vehicles.
Benjamin Franklin (17061790)
Joseph Siffred Duplessis (17251802)
Oil on canvas, 1785
Gift of the Morris and Gwendolyn Cafritz Foundation
- Electricity was a topic of much fascination for
Franklin, and he set about to study electrical phenomena
in earnest in the mid-1740s. Most people have heard
about Franklin's experiment with the kite and the key.
Explain what he was trying to prove with this demonstration.
Was it successful?
[Standard 4historical research capabilities]
Through earlier experiments and observations made
by himself and others, Franklin had concluded that electricity
was attracted to metal. In order to determine the nature
of lightning, which Franklin suspected was an electrical
current, he had to see if lightning would pass through
metal. Franklin constructed a kite with a sharp metal
wire at the top (to attract the lightning) and a metal
key tied to the bottom. While flying the kite in a thunderstorm,
lightning struck the metal wire and traveled down the
kite string to the key held by Franklin. Fortunately,
Franklin was not injured by the electrical shock he
received during this dangerous experiment, and the experiment
was a success.
Classroom activities demonstrating the properties
of electricity can be found at the Franklin Institute
Science Museum Web site (http://www.fi.edu/franklin/activity.
- Benjamin Franklin wrote a letter to an acquaintance
in France in which he said that he would like to be
embalmed and come back to see America in a hundred years.
How do you think Franklin would have reacted to seeing
America today, more than two hundred years after his
death? Imagine you are Franklin and have been granted
your wish to return to life for one day. Write an essay
in Franklin's voice, commenting upon American life in
the early twenty-first century.
[Standard 3historical analysis and interpretation]