Galileo's military compass. Page from a 17th-century work by Italian mathematician,engineer,physicist and astronomer Galileo Galilei (1564-1642),describing the use of his design of military compass. Also known as a proportional compass or a sector,this instrument is used for trigonometry,surveying,navigation and aiming artillery such as cannon. The diagram shows trigonometry being used to indirectly measure the height of a tower on a cliff. The text is in Latin,and the page is from the work 'Le operazioni del compasso geometrico,et militare di Galileo Galilei' (Padua,1606). For the instrument itself,see image C026/8917 |