From chimneys to stoves is an easy step, and the invention of the so-called Pennsylvania stove is one of his best known achievements. All his life he was an observer of the weather, and a student of the winds and tides. His first discovery in natural history was an observation of the fact that storms move against the wind, that is, for instance, that a northeast storm along the coast is felt at Philadelphia earlier than at Boston. He made a careful study of the temperature of the gulf stream in the Atlantic; and in a letter written when he was seventy-nine years old he gives a long account of his inventions and observations in nautical matters. But his discoveries in electricity quite overshadow all his other work of the sort, and on them must rest his real claim to scientific renown. For many years the world had been amusing itself with various machines for making sparks and giving shocks, and after the discovery of the Leyden jar, in 1745, the manipulation of electrical toys and machines became the rage among scientists and even among the people of society. Just about this time a friend in England sent Franklin specimens of the glass tubes used to create electricity by friction, and immediately Franklin's inquisitive mind was fired to take up the new study. So fully indeed was his attention engrossed by the series of experiments he now undertook, alone and with several investigating friends in the city, that business became irksome to him and he retired from active management of the printing house. Besides making many ingenious toys and showy experiments, Franklin added three contributions of real importance to science. 1. He anticipated Faraday in the discovery that the electricity in a charged Leyden jar resides on the glass and not on the metal coatings. He, however, made no generalizations from this discovery. 2. He advanced the fluid theory of electricity, recognizing clearly the dual nature of the varieties commonly called positive and negative from the mathematical symbols used to express them. 3. He established the identity of lightning and electricity. To understand the importance of this last discovery we must remember with what terror the world had hitherto regarded this bewildering apparition of the sky. It was not so much the dread of feeling above one an irresponsible power subject to a law that knows no sympathy with human life, as the more debasing fear of superstition, that sees in the red thunderbolt a deadly instrument of vengeance hurled by the hand of an angry deity, and that loosens the inmost sinews of a man's moral courage. With the knowledge that lightning is only a magnified electrical spark, fell one of the last strongholds of false religion. And there is something eminently fit in the fact that this lurking mystery of the heavens was finally exploded by Dr. Franklin, the exponent of common sense.