Tan′gent-scale.
(Ordnance.) A species of breech-sight for cannon. Its base has a curvature corresponding to the circumference of the breech of the gun, and its face is cut into steps corresponding to angles of elevation. The proper hight for each step is found by multiplying the natural tangent of the elevation in degrees by the distance between the base-ring and muzzle-sight. In using the scale, the required vertical line is brought to coincide with a longitudinal line at the upper part of the breech, and the top of the front-sight is viewed over the center of the step, the breech being raised or lowered until the face of the step and top of the front-sight are in the same horizontal plane.
Tangent-scale. |