Lightning Rod

Benjamin Franklin's proposal — that buildings could stop burning down in thunderstorms — turned out to be surprisingly controversial. The lightning rod, which Franklin introduced in the mid-18th century, is a simple thing: a pointed metal spike on the roof, wired down to the ground, that catches a strike and shunts the current safely into the earth. Some clergymen denounced it as impious interference with God's thunderbolts.

On 18 November 1755 a serious earthquake shook New England (the Cape Ann quake). Shortly after, Thomas Prince, the minister of Boston's Old South Church, reissued a 1727 sermon, Earthquakes the Works of God, with a new appendix. Prince speculated that "the more Points of Iron are erected round the Earth, to draw the Electrical Substance out of the Air; the more the Earth must needs be charged with it." In other words, all those Franklin rods had been quietly loading Boston with electricity, which was why the city, with more iron rods than anywhere else in New England, had been "more dreadfully shaken."

Franklin had already swatted down this kind of reasoning in a 1753 letter to his friend Cadwallader Colden: "Surely the Thunder of Heaven is no more supernatural than the Rain, Hail or Sunshine of Heaven, against the Inconveniences of which we guard by Roofs and Shades without Scruple." Harvard's John Winthrop, a natural philosopher and astronomer, gave a public lecture (November 1755) defending the rods on scientific grounds. The famous phrase about an "impious attempt to rob the Almighty of his thunder" is often pinned on Prince. It was actually John Adams, decades later, summing up the clerical mood.

Practical success gradually overcame the moral panic. What was really at stake was the authority of providence itself. Franklin's iron points proposed that human understanding could safely sit alongside it, a wager that has underwritten every scientific intervention since.