Tangent Scale

In gunnery, a bra plate, the lower edge of which is cut to fit the base-ring or base-line of the piece, and the upper edge cut into notches for each one-fourth degree elevation. It is used in pointing, by placing the lower edge on the base-ring, or base-line, with the radius of the notch corresponding with the highest point of the base-ring or line; and sighting over the centre of the notch; and the highest point of the muzzle, or top of the muzzle-sight.