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 captain,
Robert FitzRoy, had been given command in the middle of the first expedition after the previous captain committed suicide. Before being given that command, FitzRoy had been a lieutenant on board
HMS Thetis in
Rio harbour when her foremast was struck by lightning. The "fore-topmast was shivered into a mere collection of splinters" and the foremast irreparably damaged, delaying the ship for almost two months while "the foremast was taken out afterwards, and replaced by another, purchased from the Brazilian government at a great expense." Near the end of 1831, while the
Beagle was still being fitted out at
Devonport in preparation for sailing, the recently graduated
Charles Darwin arrived in Plymouth to take up the opportunity of sailing on the ship as a self-funded gentleman naturalist who would be a companion to the captain while the ship was at sea, and who would make his own expeditions inland while the ship's crew was surveying the coasts. and wrote to tell his university tutor
John Stevens Henslow about his progress, noting that he had met "one or two pleasant people, foremost of whom is Mr. Thunder & Lightning Harris, whom I daresay you have heard of." In his diary he noted that on the evening of 21 November he attended a "popular lecture from Mr Harris on his lightning conductors" at the Athenaeum. Harris used an "Electric machine" for a thunder cloud and a tub of water for the sea, then with "a toy for a line of battle ship he showed the whole process of it being struck by lightning & most satisfactorily proved how completely his plan protects the vessel from any bad consequences. This plan consists in having plates of Copper folding over each other, let in the masts & yards & so connected to the water beneath. — The principle, from which these advantages are derived, owes its utility, to the fact that the Electric fluid is weakened by being transmitted over a large surface to such an extent that no effects are perceived, even when the mast is struck by the lightning. — The Beagle is fitted with conductors on this plan; it is very probable, we shall be the means of trying & I hope proving the utility of its effects." The voyage took almost five years, and although the
Beagle was frequently exposed to lightning and was thought to have been struck by lightning on at least two occasions, "when—at the instant of a vivid flash of lightning, accompanied by a crashing peal of thunder—a hissing sound was heard on the masts; and a strange, though very slightly tremulous, motion in the ship indicated that something unusual had happened", there was never the "slightest damage".
Naval adoption of the Harris conductors Harris continued his extensive campaign to publicise the extent of the problem of lightning damage. He presented a report listing the damage caused to British naval vessels during the period from 1793 to 1838, including lightning causing 62 deaths and 114 injuries. Two study committees gave favourable recommendations for his system, but full implementation continued to be blocked by the opposition of the
First Sea Lord until a change of government led to him being replaced by a new First Sea Lord late in 1841. In June 1842 the Royal Navy at last adopted the Harris conductors. ==Selected books==