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Fascinating facts about the invention
of the
Lightning Rod by Benjamin Franklin in 1752.
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.


Benjamin Franklin Biography   from The Great Idea Finder
Invention of Bifocal Glasses   from The Great Idea Finder
Energy History    from The Great Idea Finder


Brainstorm!: The Stories of Twenty American Kid Inventors
by Tom Tucker, Richard Loehle / Paperback - 144 pages  / Sunburst (1998)
The stories of twenty ingenious young Americans who have filed patents with the United States Patent Office, including Chester Greenwood who invented ear muffs, Ralph Samuelson, originator of water-skiing, and Vanessa Hess who created colored car wax.

Flash, Crash, Rumble, and Roll
by Franklyn Mansfield Branley, True Kelley / Paperback - 32 pages / (1999) / Harpercollins Juvenile
Did you know that lightning bolts can be over a mile long? Or that they may come from clouds that are ten miles high? Storms can be scary, but not if you know what causes them.
All About Lightning
by Martin A. Uman / Paperback - 167 pages (December 1986) / Dover Pubns
The physics of lightning (voltage, current, charge, speed, event sequence, frequency of occurrence, length/width of channel, temperature, etc).
Autobiography of Benjamin Franklin
by Benjamin Franklin / Buccaneer Books / 1996
The Ben Franklin Book of Easy and Incredible Experiments
by Lisa Jo Rudy / John Wiley & Sons / 1995
What's The Big Idea, Ben Franklin?
Jean Fritz / Putnam Publications / 1976

The Franklin Institute Science Museum
A wealth of information on Franklin and Science.
Check out the online version of this Philadelphia, Pennsylvania museum.
Ben Franklin's Inventions
A list of Benjamin Franklin's inventions reveals a man of many talents and interests. It was the scientist in Ben that brought out the inventor. His natural curiosity about things and the way they work made him try to find ways to make them work better.
Franklin, Benjamin
From the Microsoft Encarta Online Encyclopedia.
Benjamin Franklin: A Documentary History
The beginnings of a biography on Benjamin Franklin. Lots of links to sources for this chronological work.

Benjamin Franklin's Autobiography
Known today as "The Autobiography of Benjamin Franklin," this classic piece of Americana was originally written for Franklin's son William, then the Governor of New Jersey. This reprint is from the original electronic text distributed by Project Gutenberg.


Reference Sources in BOLD Type This page revised January, 2005.

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