Perhaps even this step in advance might not have favoured much the cause pleaded by Mr. Snow Harris, had he not had the good fortune of finding a powerful patron in Sir George Cockburn, one of the Lords of the Admiralty. Sir George, born in London, of Scottish parents, in 1772, had all his life long taken a great interest in scientific pursuits; and the application of conductors especially had interested him much, as he had himself been a witness to frequent damage done to ships under his command by lightning. The ‘Minerva,’ of which he was captain at the blockade of Leghorn, in 1796, had been so struck, and likewise two ships of the flotilla, reducing the French island of Martinique, in 1809, under his direction. Having taken a prominent part in the American War of 1813–14, especially the capture of Washington, Sir George Cockburn retired from active service, and in 1818 was made one of the Lords Commissioners of the Admiralty, immediately after being returned a Member of Parliament for Portsmouth. He henceforth devoted himself more than ever to scientific studies; and, having been elected a Fellow of the Royal Society, got into acquaintance with many of its members, among them with Mr. Snow Harris, whom he came to like on account of his fervid enthusiasm in the cause he was advocating. The acquaintance proved of the highest advantage to the young Plymouth electrician. Before even the naval commission, nominated to give counsel upon the subject of lightning conductors, had given in its report, he was allowed to make trial, on board of several men-of-war, with a system designed by himself, and for which he had taken out a patent. It was not long afterwards that it was officially adopted for all the vessels of the Royal Navy, with, it is needless to say, the greatest pecuniary advantages to the designer.
The system of Mr. Snow Harris for protecting ships against lightning was similar to that suggested by Mr. Henly in 1774. Instead of hanging dangling chains from the top of the rigging into the water, he nailed on to the masts and down to the keel, slightly inlaid in the wood, a double set of copper plates, overlying each other in such a manner that the ends of one set were touched by the middle of the other. The plates were four feet in length, two to five inches wide, and one-eighth of an inch thick; they had holes drilled in them at distances of six inches apart, and were secured to the masts and further down by short copper nails. In order to prevent any break in the conductor at the junction of the successive masts, a copper plate was led over the cap, and the continuity preserved at all times by means of a copper hinge or tumbler which fell against the conductor. It was an altogether unobjectionable plan for securing protection against lightning, except that it was liable to fail under imperfect execution. Bad workmanship necessarily was fatal to it. The numerous copper plates had to be very neatly and carefully fastened together to ensure metallic continuity, in the absence of which the electric force might leave the path traced for it, diverging into neighbouring metallic masses, numerous on board ships, such as chains and anchors. It was a most costly system from beginning to end; but as it was, and, for the short time it remained in use, it accomplished all that was desired. Not one of the ships fitted with the conductors designed by Mr. Snow Harris was damaged by lightning, although many were struck, the electric spark in several cases being so powerful as to melt the too fine metal points on the top of the masts. However, the new lightning conductors had not to stand the ordeal of practice for any length of time. One by one the great wooden ships of war, once the pride and glory of England, went into peaceful retirement, to be replaced by iron machines, propelled by steam, metalled from the top of the masts to the water’s edge. It had been one of the recommendations of Mr. Snow Harris to the Admiralty that his copper plates, though expensive at first, would always be worth their money as old metal; and the irony of fate would have it that the conversion of copper into silver was not to be long in waiting. Before the death of the inventor, which occurred in January 1867, his lightning conductors were fast disappearing from the ships on which they were placed. From the windows of his villa at Plymouth, Sir William Snow Harris could see a fleet of ironclads, dispensing with conductors, floating on the sea.