Ligne magistrale, Fr. See [Capital line] in [Fortification].
Line of circumvallation. (Ligne de circonvallation, Fr.) See [Fortification].
Line of direction in gunnery, is a line formerly marked upon guns, by a short point upon the muzzle, and a cavity on the base ring, to direct the eye in pointing the gun.
Line of distance, the interval between two things, either in regard to time, place, or quantity.
Line of gravitation, of any heavy body, is a line drawn through its centre of gravity, and according to which it tends downwards.
Line of swiftest descent, of a heavy body, is the cycloid. See [Cycloid].
Line of projectile. See [Projectiles].
Line of the least resistance, (ligne de moindre resistance, Fr.) that line, which being drawn from the centre of the furnace or the chamber of a mine, takes a perpendicular direction towards the nearest superficial exterior.
Line of fire, (ligne de feu, Fr.) in fortification. This term admits of two distinct acceptations; first, when it is found necessary to give an idea of the manner in which a rampart, or an entrenchment overwhelms and crosses any space of ground by the discharge of ordnance or musquetry, lines must be drawn to express the distances which have been traversed by the shot, &c. These lines are called lines of fire, being an abbreviation of those lines of direction which have been given to the shot.
In order to convey a more just and accurate conception of this species of line of fire, it is recommended to give a profile, which shall not only shew the curves of the trajectories, but likewise point out the intersections and impressions which have been made by such fire upon a rampart, entrenchment, ground, or fortification of any description.