Franklin always had a deep interest in the public welfare. He started a subscription library in Philadelphia and established an academy, which finally grew into the University of Pennsylvania. Having a decidedly practical turn of mind, he had great influence in organizing a better police force and a better fire department. He invented the Franklin stove, which soon became popular because it was so much better than the open fireplace. But the most wonderful thing he ever did was proving that lightning was the same thing as electricity. Before he made this discovery, men of science had learned how to store up electricity in what is called a Leyden jar. But Franklin wished to find out something about the lightning which flashed across the clouds during a thunder-storm. Therefore, making a kite out of silk and fastening to it a small iron rod, he attached to the kite and to the iron rod a string made of hemp. One day when a thunder-cloud was coming up he went out with his little son and took his stand under a shelter in the open field. At one end of the hempen string was fastened an iron key, and to this was tied a silken string, which Franklin held in his hand. As electricity will not run through silk, by using this silken string he protected himself against the electric current. [Illustration: Franklin Experimenting with Electricity.] When the kite rose high into the air, Franklin watched intently to see what might follow. After a while the fibres of the hempen string began to move, and then, putting his knuckles near the key, Franklin drew forth sparks of electricity. He was delighted, for he had proved that the lightning in the clouds was the same thing as the electricity that men of science could make with machines. It was a great discovery and made Benjamin Franklin famous. From some of the leading universities of Europe he received the title of _Doctor_, and he was now recognized as one of the great men of the world. Franklin rendered his country distinguished public services, only a few of which we can here mention. More than twenty years before the outbreak of the Revolution, he perceived that the principal source of weakness among the colonies was their lack of union. With this great weakness in mind, Franklin proposed, in 1754, at a time when the French were threatening to cut off the English from the Ohio Valley, his famous "Plan of Union." Although it failed, it prepared the colonies for union in the struggle against King George and the English Parliament. Ten years after proposing the "Plan of Union" Franklin was sent to England, at the time of the agitation over the Stamp Act, to make a strenuous effort to prevent its passage. He was unsuccessful in accomplishing his mission, but later did much toward securing the repeal of the Stamp Act.