The essays in this volume reflect the wide-ranging interests of John D. North, distinguished historian of science and philosophy. Section One has papers on horoscopes, astrolabes and time-reckoning, and it includes an edition of a twelfth-century treatise on the astrolabe and surveys of astrolabes. Section Two is devoted to the study of the medieval cosmos. These contributions discuss Calcidian astronomy, astronomy in the Spanish Jewish community, the role of God in scholastic natural philosophy, and other themes. New information is presented about previously unknown scholars such as Abd...