Europe in the sixteenth century experienced a period of unprecedented vitality and innovation in the spheres of science and commerce. The Americans had been discovered and the colonizing nations had au urgent need for mathematical instruments for navigation and surveying. The Elizabethan age saw the establishment of the precision instrument-making trade in London, from 1540, a trade that would become world-famous in the succeeding two centuries. The mathematical instruments and charts needed by astronomers, navigators, and surveyors owe much of their development to the work of the Flemish mathematician and astronomer, Gemma Frisius, and to the map and globe maker, Gerard Mercator, both of whom studied at Louvain. It was an immigrant from Flanders, Thomas Gemini, who is credited with starting the London trade in 1540 : his reputation came from making the plates for his own printing of the Anatomy of Vesalius, and the astrolabes he made and presented to Edward VI and Elizabeth I have survived. He was followed by Humphrey Cole, and other makers whose instruments have survived, including Ryther, Knyvyn, and Whitwell. This book first describes the context in which the Elizabethan trade began, and the influence of the instruments taken to Florence by Sir Robert Dudley in 1606.The second part catalogues in detail every surviving instrument from this period, signed and unsigned, that has been traced. The catalogue is accompanied by fine photographs which illustrate both the instruments and the techniques used to identify unsigned instruments.