Circumferentor, 1676.

Made by the architect Johannes Macarius of Modena, Italy, with the inscription 'Ioannes/Macarius/Mirandolanus/Fecit Anno 1676' engraved on the alidade. Circumferentors (with a complete circle scale) and graphometers (with a half circle scale) were widely used throughout the 17th and 18th centuries to compare angles, so that the user could work out how far away a distant object was. A joint on the support allowed for both vertical and horizontal use.