Eripuit Coelo fulen, sceptrumque tyrannis, declared the former comptroller general of France, Robert Turgot, when he heard that Benjamin Franklin had died: "He snatched lightning from the sky, and the sceptre from the hands of tyrants".
The sceptre-snatching refers to Franklin's role in the American Declaration of Independence, of which he was a sign atory on July 4th, 1776. The reference to lightning recalls the kite experiment, which is believed to have taken place on this date, June 15th, in the year 1752, near Philadelphia.
During the 1740s, Franklin had become interested in the phenomenon of electricity, a subject very much in vogue, and was convinced that the lightning flashes associated with a thunderstorm were electrical in origin. We have no first-hand account of the experiment, but Franklin told his friend, the English chemist Joseph Priestly, about it and the latter recorded the story for posterity:
"The doctor, having published his method of verifying his hypothesis concerning the sameness of electricity with the matter of lightning, was waiting for the erection of a spire on Christ Church in Philadelphia to carry his views to execution. Then it occurred to him that by means of a common kite he could have better access to the regions of thunder than by any spire whatever.
"Preparing, therefore, a large silk handkerchief and two cross-sticks of a proper length on which to extend it, he took the opportunity of the first approaching thunderstorm to take a walk in the fields. But dreading the ridicule which too commonly attends unsuccessful attempts in science, he communicated his intended experiment to nobody but his son, who assisted him in raising the kite."
The kite was secured by a silken thread, near the end of which Franklin had attached a metal key.
"One very promising cloud passed over without any effect. At length, just as he was beginning to despair of his contrivance, he observed some lose threads of the hempen string to stand erect, and to avoid one another, just as if they had been suspended on a common conductor. He immediately presented his knuckle to the key, and the discovery was complete: he perceived a very evident electric spark."
Franklin was lucky to survive this dangerous experiment, but survive he did, and was immediately aware of all its implications. Now that the nature of lightning was understood, the use of "Franklin rods", or lightning conductors, became widespread in the American colonies.
Their first successful performance was reputedly in 1760 when the house of a Mr West of Philadelphia survived unscathed a direct hit by a stroke of lightning.