The efficiency of lightning conductors

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On 15 June 2012, a Methodist Church at Sutton-on-Sea (Lincolnshire) was struck by lightning during a brief but heavy and squally thundery shower in a showery southwesterly airflow. The church was protected by a lightning conductor, the main rod of which ran from a point some five feet above the highest part of the church tower and then to ground at the nearby corner of the church. A particularly loud clap of thunder was heard by people nearby, and this seems to have been the only lightning discharge to ground in the area. The roof near the lightning conductor was quite badly damaged with many roof slates broken or dislodged. It is interesting, though, that similar but less serious roof damage was also done on the opposite side of the roof (the north side) where there was no lightning conductor. It seems probable that the main lightning discharge (possibly a powerful positive charge) hit the lightning conductor, perhaps partially melting it, with a less powerful branching discharge causing the damage on the opposite side of the church roof some 20 feet or so away. Tiles and some brickwork fell into the interior of the church and the church organ did not play again for some time after the event; heavy rain fell for some 15 minutes, so that much of the interior of the church was affected by rainwater.

This episode is similar to an event in an unstable southwesterly airstream on 12 June 1781 at the Heckingham House of Industry, near Norwich, which caused both science and the Royal Society a lot of trouble and even embarrassment (Schafer, 2011). Various reports by the inmates and others caused much controversy with regard to whether the lightning conductors were the actual cause of the lightning damage. There was considerable discussion involving opposing views of distinguished members of the Royal Society on this topic: the public at this time tended not to put too much trust in the ‘men-of-letters’ – perhaps much like today over climate change (Ward, 2013).

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