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Lightning rod

The lightning rod, also called a lightning conductor, is a metal strip or rod, usually of copper, used to protect tall and isolated structures from lightning damage. A sharp pointed rod at the peak conducts the current to the ground through a low-resistance cable where it is dissipated.

In Europe the lightning rod was invented contemporaneously with but independently of Benjamin Franklin by the Czech theologian and natural scientist Vaclav Prokop Divis (1698-1765).

In America the lightning rod was invented by Benjamin Franklin as part of his groundbreaking explorations of electricity. Franklin speculated that with an iron rod sharpened to a point at the end "the electrical fire would, I think, be drawn out of a cloud silently, before it could come near enough to strike..."

Franklin had speculated about lightning rods for several years before his kite experiment. In fact, Franklin's kite experiment took place because he was tired of waiting for Christ Church in Philadelphia to be completed so he could place a lighting rod on top of it.

There was some resistance from churches who felt that it was defying divine will to install these rods. Franklin countered that there is no religious objection to roofs on buildings to resist precipitation, so lightning, which he proved is simply a giant electrical spark, should be no different. The Roman Catholic Church dropped its objection to the device in 1769 when the Church of San Nazaro, near Venice, was struck by lightning. The resulting fire ignited the 200,000 pounds of gunpowder that were being stored there at that time, creating a massive explosion which destroyed one sixth of the city of Brescia and killed 3,000 people.

The lightning rod not only protects buildings. In the 19th century it also became a symbol of American ingenuity and a decorative motif. Lightning rods were often embellished with non-functional glass balls (now prized by collectors) and incorporated into weather vanes.


  • "That I travel in thunder-storms, I grant; but not without particular precautions, such as only a lightning-rod man may know. Hark! Quick -- look at my specimen rod. Only one dollar a foot." Herman Melville, "The Lightning Rod Man", read it here (http://www.melville.org/lrman.htm)

External Link

  • The Lightning Rod (http://www.sln.org/pieces/hongell/), places Franklin's experiments in context.

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