Trials on HMS Beagle
One of the first vessels outfitted for the test was HMS Beagle, which had returned from its first survey voyage to South America, and was extensively rebuilt and refitted for the second survey voyage. As part of this work, "lightning-conductors, invented by Mr. Harris, were fixed in all the masts, the bowsprit, and even in the flying jib-boom." 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. He told his sister that he had "breakfasted yesterday with a Mr. Harris whom I like more than anybody I have seen.— He has written a great deal on Electricity", 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". Darwin himself reported this effect, and his conviction that "but for the conductor, the results would have been serious." FitzRoy reported that the copper plates stayed firmly in place, even in small spars, and strengthened the spars rather than weakening them. FitzRoy gave the lightning protection high praise:
No objection which appears to me valid, has yet been raised against them; and were I allowed to choose between having masts so fitted and the contrary, I should not have the slightest hesitation in deciding on those with Mr. Harris's conductors.
Whether they might be farther improved, as to position and other details, is for their ingenious inventor to consider and determine. He has already devoted so many years of valuable time and attention to the very important subject of defending ships against the stroke of electricity; and has succeeded so well for the benefit of others—at great inconvenience and expense to himself—that it is earnestly to be hoped that the Government, on behalf of this great maritime country, will, at the least, indemnify him for time employed and private funds expended in a public service of so useful and necessary a character.
