A. Where the gun is above the target, sight elevation equals quadrant elevation plus the angular depression of the target. Where the gun is below the target, sight elevation equals quadrant elevation minus the angular elevation of the target.
Q. How is the gunner's quadrant used?
A. It is used principally in giving elevation to mortars by first setting the movable arm such that the knife-edged tooth engages in an even-degree mark on the rack, and by moving the sliding level to read the exact number of minutes. Then it is placed on its seat at the breech, being careful to see that the arrow points in the direction of the line of fire, and by elevating or depressing the piece until the bubble comes in the middle the mortar or piece will be set at the elevation set on the quadrant. (See Fig. 67.)
THE GUNNER'S QUADRANT.
Fig. 67.
Q. Point out the following parts of the telescopic sight: Telescope, objective, eyepiece, erecting-prisms, trunnions, leveling-lug, leveling-screw, cross-level, elevation-arc, elevating-screw, vernier, focusing-collar, deflection-screw, deflection-scale, micrometer, disc, and telescope-level. (See Fig. 68.)