Thunder and lightning had mystified humanity since the beginning of recorded history. The Greeks had held that thunderbolts were launched by the god Jupiter. (One Greek philosopher, Empedocles, thought that lightning was caused by the rays of the sun striking the clouds.) Hunters of primitive tribes prayed to the god of lightning, who was a killer, as they wished to be. Certain medicine men were said to be endowed with the gift of summoning lightning at will.
Since biblical days, lightning was assumed to be an act of heavenly vengeance, but no one could explain the paradox that it struck church steeples more frequently than other buildings. In medieval times, people believed that ringing church bells would keep lightning away, a belief that survived the death of countless unfortunate bell ringers.
About 1718, an English scientist, Jonathan Edwards, suggested that thunder and lightning might be produced by a “mighty fermentation, that is some way promoted by the cool moisture, and perhaps attraction of the clouds.” There had been very few other attempts to give a scientific explanation of the phenomenon, and even in Franklin’s time many preachers considered lightning a manifestation of the Divine Will.
“Electrical fluid” and lightning had in common, Franklin wrote in his notes on November 7, 1749, that they both gave light, had a crooked direction and swift motion, and were conducted by metals. Both melted metals and could destroy animals. Since they were similar in so many respects, would it not follow that lightning, like “electrical fluid” would be attracted by pointed rods? “Let the experiment be made.”
By May 1750, he was sure enough of his hypothesis that he elaborated to Peter Collinson the advantages to humanity of what later were called lightning rods:
I am of the opinion that houses, ships, and even towers and churches may be effectually secured from the strokes of lightning ... if, instead of the round balls of wood or metal which are commonly placed on tops of weathercocks, vanes, or masts, there should be a rod of iron eight or ten feet in length, sharpened gradually to a point like a needle ... the electric fire would, I think, be drawn out of a cloud silently, before it could come near enough to strike....
Did he guess that he was on the verge of the most momentous discovery of the century—one which would assure his name a place among the immortals? It is fairly certain he was more interested in solving a perplexing problem than in immortality. Possibly he took it for granted that European scientists were already three steps ahead of him.
By July he had prepared a manuscript describing all his exciting experiments of the past two years, and including specific instructions for setting up a lightning rod on a tower or steeple, even to the necessary feature of a grounding wire. “Let the experiment be made,” he had said. He did not make it himself, not then. For one thing, he was waiting for a spire to be erected on the top of Christ Church, from which he wished to make his first try of drawing lightning from the skies. Also, in spite of his alleged retirement, his days were becoming increasingly filled with public duties.
He still had the Gazette and Poor Richard’s Almanack to publish and edit. Beginning in 1748, he served on the City Council. Since 1749 he was Grand Master of the Masons. In 1751 he was made an alderman and a member of the Pennsylvania Assembly, where previously he had served as clerk.
In 1750, an American Philosophical Society member, Dr. Thomas Bond, came to him for help in starting a hospital for the sick and the insane. Hitherto those who could not pay for medical care had no choice but the prison or the almshouse. The need was urgent but Dr. Bond had failed to arouse interest in his project.