In 1731 he was instrumental in founding the first of those public libraries, which (along with a free press) have made American tradesmen and farmers as intelligent, in Franklin's judgment, as most gentlemen from other countries, and contributed to the spirit with which they defended their liberties. The diffusion of knowledge became so general in the colonies that in 1766 Franklin was able to tell the English legislators that the seeds of liberty were universally found there and that nothing could eradicate them. Franklin became clerk of the General Assembly and postmaster, improved the paving and lighting of the city streets, and established the first fire brigade and the first police force in America. Then in 1743 in the same spirit of public beneficence Franklin put forth his _Proposal for Promoting Useful Knowledge among the British Plantations in America_. It outlines his plan for the establishment of the American Philosophical Society. Correspondence had already been established with the Royal Society of London. It is not difficult to see in Franklin the same spirit that had animated Hartlib, Boyle, Petty,[2] Wilkins, and their friends one hundred years before. In fact, Franklin was the embodiment of that union of scientific ideas and practical skill in the industries that with them was merely a pious wish. In this same year of 1743 an eclipse of the moon, which could not be seen at Philadelphia on account of a northeast storm, was yet visible at Boston, where the storm came, as Franklin learned from his brother, about an hour after the time of observation. Franklin, who knew something of fireplaces, explained the matter thus: "When I have a fire in my chimney, there is a current of air constantly flowing from the door to the chimney, but the beginning of the motion was at the chimney." So in a mill-race, water stopped by a gate is like air in a calm. When the gate is raised, the water moves forward, but the motion, so to speak, runs backward. Thus the principle was established in meteorology that northeast storms arise to the southwest. No doubt Franklin was not oblivious of the practical value of this discovery, for, as Sir Humphry Davy remarked, he in no instance exhibited that false dignity, by which philosophy is kept aloof from common applications. In fact, Franklin was rather apologetic in reference to the magic squares and circles, with which he sometimes amused his leisure, as a sort of ingenious trifling. At the very time that the question of the propagation of storms arose in his mind he had contrived the Pennsylvania fireplace, which was to achieve cheap, adequate, and uniform heating for American homes. His aspiration was for a free people, well sheltered, well fed, well clad, well instructed.