The attic of an early 1900s church tower, with plaster-on-expanded-metal-lath partitions around the structural frame:
Nice column built up of four angles and web plate. See that bare cable next to the flange on the left? That’s part of a lightning-arrestor system. Church towers badly needed those when they were built of wood or masonry, to carry the massive change from a lightning hit down to ground. Without the system, a hit would either blow the tower up or set fire to it.
But here’s the thing: you don’t actually need the cables when you’ve got a steel frame, as the frame will conduct the charge just fine, and it’s already anchored to ground. And the resistance of that cable – 3/4 inch diameter or whatever it is – is greater than the resistance of the much larger column, so the charge is going to go in the frame whether you want it to or not.
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