The main outlines of Franklin's life and career are so familiar to everyone, that I may as well pass at once to the story of his work as an inventor. We all know, or ought to know, that Benjamin, the fifteenth child of Josiah Franklin, the Boston soap-boiler, was born in that town on the 17th of January, 1706, and established himself as a printer in Philadelphia in 1728. That he prospered and founded the _Gazette_ a few years later, and became Postmaster of Philadelphia in 1737; that after valuable services to the Colonies as their agent in England, he was appointed United States Minister at the Court of France upon the Declaration of Independence; and that in 1782 he had the supreme satisfaction of signing at Paris the treaty of peace with England by which the independence of the Colonies was assured. That he died full of honors at Philadelphia in April, 1790, and that Congress, as a testimony of the gratitude of the Thirteen States and of their sorrow for his loss, appointed a general mourning throughout the States for a period of two months. [Illustration: Franklin's Birthplace, Boston.] The great invention or discovery which entitles Benjamin Franklin to rank at the head of American inventors was, of course, the identification of lightning with electricity, and his suggestion of metallic conductors so arranged as to render the discharge from the clouds a harmless one. In order to appreciate the originality and value of this discovery, it is necessary to review briefly what the world knew of the subject at that day. For a hundred years before Franklin's time, electricity had been studied in Europe without much distinct progress resulting. A thousand experiments had been performed and described. Gunpowder had been exploded by the spark from a lady's finger, and children had been insulated by hanging them from the ceiling by silk cords. A tolerable machine had been devised for exciting electricity, though most experimenters still used a glass tube. Several volumes of electrical observations and experiments had appeared, and yet what had been done was little more than a repetition on a larger scale, and with better means, of the original experiment of rubbing a piece of amber on the sleeve of the philosopher's coat. Experimenters in 1745 could produce a more powerful spark and play a greater variety of tricks with it than Dr. Gilbert, the English experimenter of 1600, but that was about all the advantage they had over him.