A MUZZLE-SIGHT of iron is screwed into the swell of the muzzle of guns, or into the middle of the muzzle-ring of howitzers. The height of this sight is equal to the dispart of the piece, so that a line joining the muzzle-sight and the pivot of the tangent scale is parallel to the axis of the piece.
38. What is a gunner’s level, or gunner’s perpendicular?
An instrument made of sheet-brass; the lower part is cut in the form of a crescent, the points of which are made of steel; a small spirit-level is fastened to one side of the plate, parallel to the line joining the points of the crescent, and a slider is fastened to the same side of the plate, perpendicular to the axis of the level.
39. What is it used for?
To mark the points of sight on pieces.
40. What is a plummet?
A simple line and bob for pointing mortars.
41. What is a gunner’s quadrant?
It is a graduated quarter of a circle of sheet-brass, attached to a brass rule 18 inches long. It has a vernier turning on a pivot, to which is attached a spirit-level. To get a required elevation, the vernier is fixed at the indicated degree, the brass rule is then inserted in the bore parallel to the axis of the piece; the gun is then elevated or depressed until the level is horizontal.
There is another graduated quadrant of wood, of 6 inches radius, attached to a rule 23.5 inches long. It has a plumb-line and bob, which are carried, when not in use, in a hole in the end of the rule, covered by a brass plate.