Pointing-wires

Are wires which are used in directing mortars. The two fixed points required in directing a mortar are determined by planting two wires upon the epaulement, one upon its crest, and the other about a yard in advance of it, both as nearly as po ible in the vertical plane pa ing through the centre of the platform and the object. The points being thus established, the direction is thus given to the mortar, by causing a plummet held in rear of it to cover the wires and the line of metal. This method is defective both in accuracy of aim and the liability of the wires being deranged by the shots of the enemy or by other causes.