Lightning rod

Franklin coined the terms "positive" and "negative" charge, rejecting du Fay's notion of two kinds of electrical fluids. He imagined that during a lightning strike, the earth and sky form a gigantic Leyden jar and flew a kite in a thunderstorm and found that the silk thread showed signs of electrical charge. He was also able to charge a real Leyden jar using this energy, proving that the two electricities were identical. Franklin generalized this idea and built tall metal spires on top of buildings, which averted lightning-induced fires, the first mitigation of natural disaster through science.
 Benjamin Franklin America 1752 Lightning rod

Franklin coined the terms "positive" and "negative" charge, rejecting du Fay's notion of two kinds of electrical fluids. He imagined that during a lightning strike, the earth and sky form a gigantic Leyden jar and flew a kite in a thunderstorm and found that the silk thread showed signs of electrical charge. He was also able to charge a real Leyden jar using this energy, proving that the two electricities were identical. Franklin generalized this idea and built tall metal spires on top of buildings, which averted lightning-induced fires, the first mitigation of natural disaster through science.