William Snow Harris - Lightning Conductor For Ships

Lightning Conductor For Ships

The lightning rod invented by Benjamin Franklin in 1752 suggested a way of avoiding the common problem of lightning causing damage to the wooden sailing ships of the period. In Britain, the Royal Navy chose a protection system with a chain draped into the sea from the top of the mast as a lightning conductor. This system proved unsatisfactory: the chain was only supposed to be raised up the mast when lightning was anticipated, and lightning often struck unexpectedly. When the chain was raised it was a nuisance to seamen aloft in the rigging to deal with the square rigged sails, and even when it was raised, lightning strokes would sometimes damage the chain or the ship. There were also fears that the conductors would attract lightning to the ship, and prejudices against their use. The French navy devised a modified system in which the chain was led down the permanent rigging to connect to the copper sheathing which was used to protect the hull below the waterline against damage from collisions and shipworms. In the early 19th century they replaced the chains by metal cables.

Harris invented a new system in 1820, with lightning conductor plates fixed along spars and down the aft side of the mast, right down through the hull to connect to the copper sheathing of the hull. All the principal metallic masses in the ship were to be bonded to the conductor to ensure that there were no side flashes. He proposed this system to the Admiralty in 1821 but found them unresponsive to his proposals, and he campaigned to persuade the Navy to test his system, and to publicise the extent of the problem. They agreed to test the system on eleven vessels, starting in 1830.