Autograph Letter Signed ‘William Snow Harris’, to Davies Gilbert, about the dispatch of his paper to the Royal Society, and thanking Gilbert “for the kind interest you have shewn on this occasion respecting my paper”. 1 page 7½ x 4¾ inches, some marginal staining, integral blank leaf (stained on verso where formerly mounted). Plymouth, 23 May 1830. Uncommon. Sir William Snow Harris (1791–1867) was an English physician and electrical researcher, nicknamed Thunder-and-Lightning Harris, and noted for his invention of a successful system of lightning conductors for ships. It took many years of campaigning, research and successful testing before the British Royal Navy changed to Harris’s conductors from their previous less effective system. One of the successful test vessels was HMS Beagle which survived lightning strikes unharmed on her famous voyage with Charles Darwin.