William Gilbert (1544-1603) was the most distinguished man of science in England during the reign of Queen Elizabeth I. The first person to use the terms electric attraction, electrical force and magnetic pole, he is considered to be the father of electrical studies. Gilbert's world was that of Elizabeth's royal court, a hive of elite mariners and navigators. Through them, he came to hear of a new discovery made by a retired sailor turned compass-maker, the magnetic 'dip'. Using some of the first examples of experimental method ever recorded, Gilbert came to consider the Earth as one vast spherical magnet, with the accompanying ability to determine much more accurately a ship's latitude at sea. This was the golden age of circumnavigation, of discovering new lands and new trade routes, and of the settling of new colonies. Unfolding the drama of Gilbert's discoveries, this book climaxes with an exploration of geomagnetism, via the story of longitude schemes so crucial to today's seafarers.