This gunner's quadrant is composed of two flat legs of uneven length, joined at a right angle. A graduated arc enabled made it possible—presumably with the use of a plumb bob tied in the corner—to measure scarp-wall gradients and gun elevations. The model from which this example derives is described by Niccolò Tartaglia in Nova scientia (Venice, 1537). Provenance: Vincenzo Viviani bequest.