But a new career was opened to Franklin with the attainment of leisure and independence,--the career of a scientific investigator. The subject which most interested him was electricity, just then exciting great interest in Europe. In 1746 he attended in Boston a lecture on electricity by Dr. Spence, of Scotland, which induced him to make experiments himself, the result of which was to demonstrate to his mind the identity of the electrical current with lightning. What the new, mysterious power was, of course he could not tell, nor could any one else. All he knew was that sparks, under certain conditions, were emitted from clothing, furs, amber, jet, glass, sealing-wax, and other substances when excited by friction, and that the power thus producing the electric sparks would repel and attract. That amber, when rubbed, possesses the property of attracting and repelling light bodies was known to Thales and Pliny, and subsequent philosophers discovered that other substances also were capable of electrical excitation. In process of time Otto Guericke added to these simple discoveries that of electric light, still further established by Isaac Newton, with his glass globe. A Dutch philosopher at Leyden, having observed that excited electrics soon lost their electricity in the open air, especially when the air was full of moisture, conceived the idea that the electricity of bodies might be retained by surrounding them with bodies which did not conduct it; and in 1745 the Leyden jar was invented, which led to the knowledge that the force of electricity could be extended through an indefinite circuit. The French savants conveyed the electric current through a circuit of twelve thousand feet.
It belonged to Franklin, however, to raise the knowledge of electricity to the dignity of a science. By a series of experiments, extending from 1747 to 1760, he established the fact that electricity is not created by friction, but merely collected from its state of diffusion through other matter to which it has been attracted. He showed further that all the phenomena produced by electricity had their counterparts in lightning. As it was obvious that thunder clouds contained an immense quantity of the electrical element, he devised a means to draw it from the clouds by rods erected on elevated buildings. As this was not sufficiently demonstrative he succeeded at length in drawing the lightning from the clouds by means of a kite and silken string, so as to ignite spirits and other combustible substances by an electric spark similar to those from a Leyden jar. To utilize his discovery of the identity of lightning with electricity he erected lightning-rods to protect buildings, that is, to convey the lightning from the overhanging clouds through conductors to the ground. The importance of these lightning-rods was doubtless exaggerated. It is now thought by high scientific authorities that tall trees around a house are safer conductors in a thunder storm than metallic rods; but his invention was universally prized most highly for more than one hundred years, and his various further experiments and researches raised his fame as a philosopher throughout Europe. His house was a museum of electrical apparatus, and he became the foremost electrician in the world. His essays on the subject were collected and printed abroad, and translated into several languages, and among the scientists and philosophers of Europe he was the best known American of his time; while at home both Harvard and Yale Colleges conferred on this self-educated printers-apprentice the degree of Master of Arts.
The inquiring mind of Franklin did not rest with experiments in the heavens. As a wealthy and independent citizen of Philadelphia he interested himself in all matters of public improvement. He founded a philosophical society to spread useful knowledge of all kinds. He laid the foundation of what is now the University of Pennsylvania, and secured a charter from George II.; but he had little sympathy with the teaching of dead languages, attaching much more importance to the knowledge of French and Spanish than of Latin and Greek. We see in all his public improvements the utilitarian spirit which has marked the genius of this country, but a spirit directed into philanthropic channels. Hence he secured funds to build a hospital, which has grown into one of the largest in the United States. He established the first fire company in Philadelphia, as well as the first fire insurance company; he induced the citizens of Philadelphia to pave and sweep their streets, which were almost impassable in rainy weather; he reorganized the night-watch of the town; he improved the street-lighting; he was the trustee of a society to aid German immigrants; he started a volunteer military organization for defence of the State against the Indians; he made a new fertilizer for the use of farmers; he invented the open "Franklin stove" to save heat and remedy the intolerable smoky chimneys which the large flues of the time made very common; he introduced into Pennsylvania the culture of the vine; in short, he was always on the alert to improve the material condition of the people. Nor did he neglect their intellectual improvement, inciting them to the formation of debating societies, and founding libraries. His intent, however, was avowedly utilitarian, to "supply the vulgar wants of mankind," which he placed above any form of spiritual philosophy,--inculcating always the worldly expediency of good character and the poor economy of vice. Herein he agreed with Macaulay's idea of progress as brought out in his essay on Lord Bacon. He never soared beyond this theory in his views of life and duty. The Puritanic idea of spiritual loftiness he never reached and never appreciated.
But it was not as a public-spirited citizen, nor as a successful man of business, nor even as a scientific investigator, that Franklin earned his permanent fame. In each of these respects he has been surpassed by men of whom little is known. These activities might have elevated him into notice and distinction, but would not have made him an immortal benefactor to his country. It was his services as a diplomatist and a political oracle, united with his patriotism and wisdom, that gave to him his extraordinary prominence in American history.
