On June 10th, 1752, Benjamin Franklin did a very dangerous thing. He flew a kite on a stormy day, trying to find out if lightening was electricity.

Today, we would say, “Mr. Franklin, of course lightning is electricity. Everyone knows that.”

But in 1752, no one knew that. Electricity was something many people were interested in, but nobody knew much about it. And there were not any practical uses for it yet: no light bulbs, no electric cookers, no electric clocks, nothing useful.

However, this force seemed magical, and people were experimenting with it as best they could.

In the 1700s, electricity was not new. People had known about it for thousands of years, mostly from certain animals, such as electric eels, that can store electricity in their bodies and give a painful shock if you touch them.

In Egypt as early as 3100 BC, there were catfish in the Nile River that could produce 350 volts. Ancient Egyptians called them “angry catfish” and believed they were protectors of other fish. Some people there would use shocks from the catfish to treat certain diseases.

Ancient Greeks figured out that if you rubbed a piece of amber with a piece of fur, a spark would result. In 1600, an English scientist named William Gilbert used an old Greek word for amber (elec) to form a new word, electricus, from which we get the words electric and electricity.

Benjamin Franklin was fascinated by electricity and in the 1750s did many experiments, trying to learn more about it. A few years earlier, a device called a Leyden Jar had been invented in Germany. It stored static electricity. It was Ben Franklin who came up with the word battery to describe such things.

One time while experimenting with Leyden Jars, Franklin almost electrocuted himself. The jolt knocked him out for a minute and took several days to recover from. This, however, did not dim his curiosity or desire to learn more.

In a letter, Franklin described an idea for an experiment that would tell if lightning was electric or not. He called the experiment the Sentry Box. Guards or sentries often had a small shelter, called a guard box or sentry box, to protect them from rain.

Franklin’s idea was to put up a metal rod with a wire leading from it. The wire would have a kink in it that would spark if electricity traveled down the wire. An observer would stand in the box, safe and dry, and watch the kinked wire.

Franklin didn’t actually do the sentry box experiment because he thought the metal rod needed to be much higher, so he came up with a new idea: fly a kite in a storm. The kite would have a metal rod on it that would be attached to the kite string. If lightening was electric, then electricity would travel down the wet kite string and make a key tied to the string spark.

Having learned his lesson from the Leyden Jar mishap, Franklin took no chances. He stood in a dry place and held a dry length of silk rope that was tied to the key. That way, if electricity traveled down the wet string to the key, it would not travel from the key to him. Sure enough, electricity came down the wet string and made the key spark. Franklin reached out a knuckle, and the spark jumped from the key to his knuckle. This confirmed to Franklin that lightning is indeed electricity.

Some people say that Franklin didn’t really do the kite experiment because he didn’t describe it in any letters. However, Franklin said that he did the experiment, and he was a very truthful person who wouldn’t have said he did it if he hadn’t.

People also say he couldn’t have done the kite experiment because if lightning struck the kite, it would have killed him. Clouds in a storm are electrically charged and even without an actual lightning strike they could send a charge down the string powerful enough to make the key spark, but not be deadly.

Do not try the kite experiment yourself. It’s way too dangerous.

Fun Facts.

•  In the movie, Jurassic Park, there is a good explanation of how amber is formed, showing in a cartoon presentation how ancient tree sap, over millions of years, hardens into a clear, lovely, stone-like substance.

•  Electric catfish exist today and are mostly found in Africa and in the Nile River.

•  People mistakenly say that Franklin discovered electricity with his kite experiment. He didn’t discover electricity, he discovered that lightning and electricity are the same thing.

•  Franklin’s kite and sentry box experiments led to his invention of the lightning rod. Lightning rods are used, even today, to protect buildings from being damaged by lightening strikes.