Franklin began to make experiments in electricity when he was about forty years old.

He was the first person to discover that lightning is caused by electricity.  He had long thought that this was true, but he had no means of proving it.

He thought that if he could stand on some high tower during a thunder-storm, he might be able to draw some of the electricity from the clouds through a pointed iron rod.  But there was no high tower in Philadelphia.  There was not even a tall church spire.

At last he thought of making a kite and sending it up to the clouds.  A paper kite, however, would be ruined by the rain and would not fly to any great height.

So instead of paper he used a light silk handkerchief which he fastened to two slender but strong cross pieces.  At the top of the kite he placed a pointed iron rod.  The string was of hemp, except a short piece at the lower end, which was of silk.  At the end of the hemp string an iron key was tied.

“I think that is a queer kind of kite,” said Franklin’s little boy.  “What are you going to do with it?”

“Wait until the next thunder-storm, and you will see,” said Franklin.  “You may go with me and we will send it up to the clouds.”

He told no one else about it, for if the experiment should fail, he did not care to have everybody laugh at him.

At last, one day, a thunder-storm came up, and Franklin, with his son, went out into a field to fly his kite.  There was a steady breeze, and it was easy to send the kite far up towards the clouds.

Then, holding the silken end of the string, Franklin stood under a little shed in the field, and watched to see what would happen.

The lightnings flashed, the thunder rolled, but there was no sign of electricity in the kite.  At last, when he was about to give up the experiment, Franklin saw the loose fibres of his hempen string begin to move.

He put his knuckles close to the key, and sparks of fire came flying to his hand.  He was wild with delight.  The sparks of fire were electricity; he had drawn them from the clouds.

That experiment, if Franklin had only known it, was a very dangerous one.  It was fortunate for him, and for the world, that he suffered no harm.  More than one person who has since tried to draw electricity from the clouds has been killed by the lightning that has flashed down the hempen kite string.

When Franklin’s discovery was made known it caused great excitement among the learned men of Europe.  They could not believe it was true until some of them had proved it by similar experiments.

They could hardly believe that a man in the far-away city of Philadelphia could make a discovery which they had never thought of as possible.  Indeed, how could an American do anything that was worth doing?

Franklin soon became famous in foreign countries as a philosopher and man of science.  The universities of Oxford and Edinburgh honored him by conferring upon him their highest degrees.  He was now Doctor Benjamin Franklin.  But in America people still thought of him only as a man of affairs, as a great printer, and as the editor of Poor Richard’s Almanac.