1-154-908 - Oxford Science Archive/Heritage Images

John Harrison, c1835. Portrait of the English inventor and horologist wearing a wig. Harrison became famous for resolving one of the most problematic issues of his day - how to determine longitude while at sea. This was to take him over forty years, during which time he devised many other ways to improve the accuracy of time-keeping. The celebrated horologist is shown seated next to the H4 marine chronometer which was to make him world-famous.