This altazimuth quadrant is called a Cassini quadrant (after Giovanni Domenico Cassini). A frame is placed upright on a graduated brass arc. A small telescope slides along the graduated arc of a second quadrant attached to the frame. A second finder telescope pivots on a small pillar. The instrument served to measure vertical and horizontal angles and perform astronomical and topographic observations (such as determining the time and latitude). This specimen was built by a French maker named Dubois, about whom we have no information. Provenance: Lorraine collections.