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Benjamin Franklin: Science Years
(Ages 40 - 49)
by Ron Kurtus (revised 17 December 2005)
From the age of 12 to 39, Benjamin Franklin worked in the publisher business in Philadelphia. He then retired from publishing and turned to scientific studies. His inventions and experiments in science soon brought him world-wide fame. His most notible experiments were with electricity.
Questions you may have include:
- What were his inventions and discoveries?
- What did he do concerning electricity?
- How did he come up with his ideas?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
Ages 40 to 46 (1746 - 1752)
http://www.ideafinder.com/history/inventions/lightningrod.htm
Benjamin Franklin was fascinated by storms; he loved to study them. If he were alive today, we could probably add "storm-chaser" to his long list of titles.
It was in Boston, Massachusetts, in 1746 that Franklin first stumbled upon other scientists' electrical experiments. He quickly turned his home into a little laboratory, using machines made out of items he found around the house. During one experiment, Ben accidentally shocked himself. Franklin spent the summer of 1747 conducting a series of groundbreaking experiments with electricity. He wrote down all of his results and ideas for future experiments in letters to Peter Collinson, a fellow scientist and friend in London who was interested in publishing his work. By July, Ben used the terms positive and negative (plus and minus) to describe electricity, instead of the previously used words "vitreous" and "resinous." Franklin described the concept of an electrical battery in a letter to Collinson in the spring of 1749, but he wasn't sure how it could be useful.
Later the same year, he explained what he believed were similarities between electricity and lightning, such as the color of the light, its crooked direction, crackling noise, and other things. There were other scientists who believed that lightning was electricity, but Franklin was determined to find a method of proving it.By 1750, in addition to wanting to prove that lightning was electricity, Franklin began to think about protecting people, buildings, and other structures from lightning. This grew into his idea for the lightning rod. Franklin described an iron rod about 8 or 10 feet long that was sharpened to a point at the end. He wrote, "the electrical fire would, I think, be drawn out of a cloud silently, before it could come near enough to strike..." Two years later, Franklin decided to try his own lightning experiment. Surprisingly, he never wrote letters about the legendary kite experiment; someone else wrote the only account 15 years after it took place.
In June of 1752, Franklin was in Philadelphia, waiting for the steeple on top of Christ Church to be completed for his experiment (the steeple would act as the "lightning rod"). He grew impatient, and decided that a kite would be able to get close to the storm clouds just as well. Ben needed to figure out what he would use to attract an electrical charge; he decided on a metal key, and attached it to the kite. Then he tied the kite string to an insulating silk ribbon for the knuckles of his hand. Even though this was a very dangerous experiment, (you can see what our lightning rod at the top of the page looks like after getting struck), some people believe that Ben wasn't injured because he didn't conduct his test during the worst part of the storm. At the first sign of the key receiving an electrical charge from the air, Franklin knew that lightning was a form of electricity. His 21-year-old son William was the only witness to the event.
Two years before the kite and key experiment, Ben had observed that a sharp iron needle would conduct electricity away from a charged metal sphere. He first theorized that lightning might be preventable by using an elevated iron rod connected to earth to empty static from a cloud.
Franklin began to advocate lightning rods that had sharp points. His English colleagues favored blunt-tipped lightning rods, reasoning that sharp ones attracted lightning and increased the risk of strikes; they thought blunt rods were less likely to be struck. King George III had his palace equipped with a blunt lightning rod. When it came time to equip the colonies' buildings with lightning rods, the decision became a political statement. The favored pointed lightning rod expressed support for Franklin's theories of protecting public buildings and the rejection of theories supported by the King. The English thought this was just another way for the flourishing colonies to be disobedient to them.
Franklin's lightning rods could soon be found protecting many buildings and homes. The lightning rod constructed on the dome of the State House in Maryland was the largest "Franklin" lightning rod ever attached to a public or private building in Ben's lifetime. It was built in accord with his recommendations and has had only one recorded instance of lightning damage. The pointed lightning rod placed on the State House and other buildings became a symbol of the ingenuity and independence of a young, thriving nation, as well as the intellect and inventiveness of Benjamin Franklin.
At age 42, Franklin retired from the printing profession. He then devoted his time to other studies, especially science. These were very productive years in his life, bringing him world-wide fame as a scientific thinker.
Interested in electricity
Franklin was ever curious and inquisitive. He became interested in electricity after seeing demonstrations about static charges and the Leyden Jar. Afterwards, he used a method of rubbing glass tubes with silk to generate the static electric charges that could be used in many of his experiments.
Invented lightning rod
Franklin felt that lightning was electricity that came from the clouds. To prove this theory, he set up tall, pointed metal rods to provided a path for the electricity of lightning to follow. His experiments in attracting lightning to the rods resulted in the invention of the lightning rod, designed to protect people's dwellings.
Because of the invention, Franklin received accolades. But he remained modest and even refused to patent the lightning rod or attempt to profit from it.
Performed kite experiment
To continue his study of the relationship of lightning and electricity, the 46 year old Franklin devised his famous kite experiment with the aid of his 21 year old son, William.
One day, during a thunderstorm, he flew a kite in the storm. Little did he know that this was a very dangerous thing to do.
Franklin flying kite with his son
(Note: Either 21 year old William was very small for his age, or the artist goofed)
He had attached a metal key to the end of the kite string. As the rain fell and the wind blew, he noticed the hairs on the kite string stand on end, just as they would do if you combed your hair and put the comb near the string. He was able to make a spark jump from the key to his finger.
Luckily, he ended his experiment then, because he easily could have been electrocuted from his experiment. Franklin seemed only dimly aware of the experiment's potential danger.
Invented lightning bells
Also at age 46, Franklin developed another device to help him understand electricity, called lightning bells. These bells would jingle when lightning was in the air.
Did another risky experiment
To make these lightning bells work, Franklin used the lightning rod he had erected on his roof and ran a wire from it into his house. He divided the wire into two wires, which were attached to two small bells separated by 6 inches.
Between the bells was a little brass ball, suspended by a silk thread. When storm clouds passed with electricity in them, the ball would go back and forth, ringing the bells.
Franklin was fortunate to disconnect his experiment before a lightning bolt struck the rod and set his house on fire.
Lucky not killed
Although his scientific curiosity moved him toward inventive experiments, he was lucky he was never killed with these dangerous experiments. Once he received such a severe electrical shock that his body actually went into seizures. He was more careful after that.
Became famous
Franklin's electrical experiments brought him instant fame, and crowds began to gather around his home, hoping to catch a glimpse of the "wizard of electricity."
Started fire insurance
In his 46th year, he also was responsible for setting up America's first fire insurance company.
The year 1752 certainly was an active time in his life.
Ages 47 to 49 (1753 - 1755)
The next several years Franklin continued his scientific studies, as well as creating useful inventions.
Coined electrical terms
Franklin coined many of the electrical terms we use today, such as battery, conductor, condenser, positive and negative charge, electric shock and electrician.
Had several inventions
Franklin studied other scientific areas than electricity. He invented the catheter, bifocals, and the Franklin stove, among other things.
Catheter
Ben examined medicine and invented the medical instrument known as a catheter in order to treat his ill brother. He also formulated theories about the circulation of blood in humans.
Bifocals
Franklin wore glasses, and after the age of 40 he needed another pair for reading. To solve that problem, he split the lenses of each pair of glasses, such that the top half was for distances and the bottom half was for reading. In this way, he would not have to constantly change his glasses. This was the invention of the bifocal glasses.
Franklin Stove
Franklin was always noticing problems or irritations and trying to solve them. For example, when he noticed the problem of heating houses, Franklin invented a type of stove that would do the job more effectively. This was called the Franklin Stove.
Background of his genius
What made his achievements during these years even more remarkable was the fact that Franklin had no formal education in the sciences. He relied purely on his powers of observation, his personal intellect and curiosity.
Since he was an amicable person with a good sense of humor, he had many friends—including those who specialized in science. From letters and conversations with these scientists, Franklin gained insight and ideas for his experiments.
Also, part of Franklin's genius was that he sought to master every endeavor that he put his mind to, from printing to science to politics.
Summary
During the years in his 40s, Benjamin Franklin gained fame through his experiments in electricity. He also came up with a number of inventions during this time of scientific study. He was inquisitive and observant, leading to his discoveries. In the later years of his life, he spent more time on statesmanship, representing his country in Europe.
Learn by experimenting
Resources
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Mini-quiz to check your understanding
If you got all three correct, you are on your way to becoming a Champion in understanding the Biographies of famous people. If you had problems, you had better look over the material again.
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Where can you go from here?
Benjamin Franklin:
Publishing Years (Birth to Age 39) >
Science Years (Ages 40 - 49) >
Statesman Years (Ages 50 - 84) >
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