Dr. Franklin experimenting with his kite.
Silk, I have told you, is one of the non-conductors. Dr. Franklin made use of silk in the experiment by which he discovered that lightning and electricity are the same thing. He managed in this way: He made his kite of a large silk handkerchief instead of paper. He had on it a pointed iron wire, and the string of the kite was fastened to this wire. This kite he sent up in a thunder-storm, when there was a plenty of electricity in the clouds. The iron wire would of course receive some of the electricity, and it would not go from the wire to the kite, because that was made of silk, which, you know, is a non-conductor. It would go down the string, this being tied to the wire. Passing down the string, it would go to Dr. Franklin’s hand, and down his body into the earth. It would do this silently, because it would keep going a little at a time all the while. But he managed to prevent the electricity from coming to his hand. He stopped it on the way. He did this by tying a silk ribbon to the hemp string, and holding the kite by this ribbon, as you see in the picture. The electricity could not go through this silk, and so it staid in the hemp string.
How Dr. Franklin drew the lightning down from the clouds.
Dr. Franklin now fastened a key to the end of the hemp string. A great deal of the electricity now passed to the key, because the metal of which the key was made was so good a conductor. It was a much better conductor than the string, and so the electricity, as we may say, spread all over it. It was a real receiver of the electricity, like the brass receiver of the electrical machine. Accordingly, when Franklin put his knuckle near the key, he received a shock from it, just as one does from the knob of the brass receiver. After a little time it began to rain, and then the shocks were harder. The reason was, that the string, when wet, was a better conductor than when dry, and so the electricity came on it faster to the key.
In this way Dr. Franklin drew the lightning down from the clouds in so small a quantity that he could find out what it was. He found that it was just the same as the electricity that we make by the electrical machine, and he could bottle it up in the same way that we do the electricity from the brass receiver. This he could do by holding the Leyden jar with its brass knob to the key. The electricity would go into it just as it does from the receiver when we are working the machine.
What Franklin proved.
Before Franklin tried this experiment with his kite it was supposed that the lightning was electricity, but it was only supposition. No one knew that it was so. It was never proved till Franklin sent up his silk kite to find out about it. It was supposed that lightning was electricity simply because the effects of lightning were similar to the effects of the electricity of the machine when a great deal of this electricity was made. Experiments were tried which showed that the machine electricity, when there was enough of it, tore things to pieces, and killed animals, just as lightning does; but the difficulty was that no one had ever seen what a little of the lightning would do. This Franklin found out by bringing some of it down out of the clouds by the string of his kite, and bottling it up for use in the Leyden jar. Before his experiments nothing was known about lightning except as it was seen in large quantities going from cloud to cloud, or coming down to the earth and shivering a tree, or plowing up the ground, or perhaps killing some animal or some man. Nothing was known of it in a small way until Franklin showed us so much about it by his experiments.
Suggested the use of lightning-rods.
Lightning-rods protect in two ways.