In the eighteenth century, wealthy and influential men often interested themselves in more than one branch of learning. The American Benjamin Franklin was a statesman, printer, author and scientist. He left school at twelve, being the fifteenth child of seventeen, but soon made up for his lack of formal education. As well as his political work, he conducted many experiments concerning electricity. In 1752, he flew a kite in a thunder-storm, attaching a metal key to the damp string. An electrical charge ran down the string and Franklin was able to feel it jump to his finger when he approached the key. From this he concluded that lightning was an electrical spark and in 1753 launched his invention of the lightning conductor.
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, 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 articulated these thoughts as he pondered the usefulness of a lightning rod.
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