The first major improvement to the mariner's compass came in the mid-18th century with the work of Dr Gowin Knight. In 1745 he invented a method of making strongly magnetic steel bars, and then developed a steel compass needle which retained its magnetism for much longer than the old soft iron kind. George Adams, the London instrument maker, was employed as agent for Knight's compasses and this example has the signature 'Gowin Knight 1180' on the back of the card.