The rope is given five feet slack for recoil.
Fig. 54.
The Pointing-scale.—This is made of hard wood, graduated on one side, the unit of the scale being one thousandth of the range, and each division one five hundredth of the range. A brass index-slide moves with friction along the scale and is clamped by a screw when regulated. For reference-marks a brass screw is placed at the end of each cheek of the carriage, and the scale is so arranged that it can be applied to either cheek. The carriage admits of a motion around its pintle of about 15° on either side of the axis of the platform.
THE GUNNER'S QUADRANT.
Fig. 55.
Used in giving elevation. The arc is 45°, but by applying different sides an elevation of 90° can be given. The least reading is one minute, which is given by the setting of a sliding level on a slightly curved arm.
The setting to any given degree is made by moving the arm by hand, which is done by pressing back the head of the arm to release it from engagement with the notches on the interior of the arc, then moving the arm to the required position and allowing the spring to react.