Chapter X: Part II: Section II

POINTING MORTARS.

1. What is the rule for pointing mortars?

First give the elevation, and then the direction.

2. How is the elevation given?

By applying the quadrant to the face of the piece, and adjusting the quoin until the required number of degrees is indicated.

3. Are the same means employed for giving mortars their direction as those which are used with guns and howitzers?

No; because mortars are usually masked from the object to be struck, by an epaulment or parapet.

4. To what are all the methods employed for giving the direction to mortars reduced?

To determining practically two fixed points, which shall be in line with the piece and the object, and sufficiently near to be readily distinguished by the eye. These points being covered by the plummet, determine a vertical plane, which, when including the line of metal, becomes the plane of fire.

5. What is the simplest manner of directing the mortar?

By means of _pointing-wires_.

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6. Describe this method.

The two fixed points required are determined by planting two wires upon the epaulment, one upon its crest, and the other about a yard in advance of it, both as nearly as possible in the vertical plane passing through the centre of the platform and the object. The points being thus established, the direction is given to the mortar, by causing a plummet held in rear of it, to cover the wires and the line of metal.

7. In what respects is this method defective?

Both in accuracy of aim, and the liability of the wires being deranged by the shots of the enemy or by other causes.

8. Give a better method.

By means of _pointing-stakes_, by which one of the fixed points is established upon the crest of the parapet, or at the toot of the interior slope, and another in rear of the piece. Then by a cord called the _pointing-cord_, stretched between these two points, with the plummet suspended from it, a vertical plane is determined with which the line of metal is made to coincide.

9. How are the stakes planted?

A stake, a foot or more in length, is driven into the crest of the epaulment, as nearly as practicable in the vertical plane of fire passing through the centre of the platform; sighting by this stake, another long one is planted, three or four feet in front of it, in line with the object. To this stake the cord is temporarily attached, and stretched by the first stake, just grazing it, to a point on the ground, one yard in rear of the platform. At this point a third stake is driven. The cord is removed from the second stake, which may now be taken away, and permanently attached to the first.

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10. How is the mortar directed?

The cord is stretched to the rear stake, and as near the muzzle-band as possible, with the left hand, while the plummet is suspended against it with the right; or the plummet may be attached to the cord, just in rear of the mortar.

11. How does it appear that the mortar is thus _properly_ directed?

Because the cord, the plummet, and the line of metal, are evidently in the vertical plane of fire.

12. What is done in case the shell should strike constantly to the right or left of the object?

The pointing-cord is shifted to some notch on the _pointing-board_, to the right or left, until the shell falls at the desired point.

13. Describe the pointing-board.

This is a piece of wood one foot long, two or three inches wide, and one inch thick, having a notch cut in the middle of one side, to fit on the stake and which is graduated into equal divisions from its middle. When not in use, the pointing-cord may be wound on it.

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14. Describe another mode of planting the _pointing-stakes_.

The mortar being placed upon the middle of the platform, the gunner mounts upon it, and suspends the plummet in front of the muzzle, covering the object. Where the plummet thus suspended cuts the crest of the epaulment, the first stake is driven. A second stake is then driven in the same line between the mortar and the epaulment. The pointing-cord being attached to the first stake and stretched to the rear, over the point where the plummet touches the top of the mortar, determines the point on the ground at which the rear stake is driven. The first stake is then removed, and the cord attached permanently to the second stake.

When the object cannot be seen from the mortar, owing to the interposition of some obstacle, as a parapet or a hill, two persons in sight of each other, one of whom can see the mortar, and the other the object, must by successive changes of position, place themselves in the vertical plane of fire, and at the points thus determined, stakes must be driven, one of which will serve as the object.

15. How may precision of fire be secured at night with mortars?

The _direction_ is preserved by nailing or screwing two boards to the platform outside of the cheeks; the _elevation_ is marked on the quoin, or the quoin may be nailed in the proper position.

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