John Dee was best known as a mathematician to his contemporaries, and it is in this capacity that Dee is most frequently mentioned for fifty years after his death. From mathematics he branched out into the study of astrology and, more profitably for his compatriots, into instruction in navigation, so that his influence is apparent in the early voyages of the Muscovy Company and is believed to have contributed to Sir Francis Drake's world voyage of 1577-1580. There can be no doubt of the extent of his learning and of his influence in many areas, including the British expansion into the New World. Dee's learning was based on the possession of one of the three largest English libraries of the sixteenth century. Unlike his rivals in collecting,John, Lord Lumley, and Andrew Perne, Dee played a major part in saving and encouraging others to save manuscripts from the...