Chapter VI: Part I: Section V

ON MORTARS.

1. What is a _Mortar_?

The shortest piece in service; the trunnions are placed in rear of the vent at the breech; the bore is very large in proportion to the length, and is provided with a chamber.

2. What are the principal advantages obtained by the employment of mortars?

Reaching objects by their vertical fire—such as a town, battery, or other place—whose destruction or injury cannot be effected by direct or ricochet fire; dismounting the enemy’s artillery; setting fire to and overthrowing works; blowing up magazines; breaking through the roofs of barracks, casemates, &c.; and producing havoc and disorder amongst troops.

3. What do you mean by vertical fire?

That produced by firing the mortar at a high elevation.

4. What are its advantages?

The shell having attained a great elevation, descends with great force on the object, in consequence of the constant action of the force of gravity on it.

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5. Why are mortars constructed stronger and shorter than other pieces?

Because greater resistance is required in consequence of the high elevation under which they are fired; and were they longer, the difficulty experienced in loading them would become too great.

6. Why is a mortar constructed with a chamber?

In consequence of employing various charges, some very small, it becomes necessary to use a chamber to concentrate the charge as much as possible, so that the shell may be acted on by the entire expansive force of the powder.

7. What form of chamber is given to mortars?

Usually that of a frustum of a cone. The bottom is hemispherical in the sea-coast, stone, and eprouvette mortars. In siege mortars it is a plane surface, the angles of intersection being rounded in profile by arcs of circles.

8. What is this form of chamber called?

Gomer Chamber.

9. What is the advantage of the conical over the cylindrical chamber?

Cylindrical chambers are objectionable, as the projectile is frequently broken in consequence of the small surface exposed to the action of the charge. This defect is obviated by large chambers, and particularly by those that are conical, in which the charge is expended upon nearly a hemisphere.

10. What form of chamber has the eprouvette?

That of a cylinder, it being the only mortar whose chamber is of this shape.

11. How are mortars mounted?

On beds of wood or iron.

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12. What is the object of mounting mortars on beds in preference to wheel carriages?

On account of the high elevation at which they are usually fired, when the recoil, instead of forcing the piece backwards, tends to force it downwards, and this tendency becomes so great at the higher angles that no wheel carriage could long sustain the shock.

13. What is the entire length of each mortar?

13-inch, 53 inches; 10-inch sea-coast, 46 inches; 10-inch siege, 28 inches; 8-inch, 32.5 inches; stone mortar, 31.55 inches; coehorn, 16.32 inches.

14. What are the weights of mortars?

13-in., 11,500 lbs.; 10-in. sea-coast, 5,775 lbs.; 10-in. siege, 1,852 lbs.; 8-in., 930 lbs.; stone mortar, 1,500 lbs.; coehorn, 164 lbs.; eprouvette, 220 lbs.

15. What are the weights of the different mortar beds?

8-in. siege, 920 lbs.; 10-in. siege, 1,830 lbs.; coehorn, 132 lbs.; eprouvette, 280 lbs.

16. What are the diameters of the bores of the stone, coehorn, and eprouvette mortars?

Stone mortar, 16 inches; coehorn, 5.82 inches; eprouvette, 5.655 inches.

17. What is the length of the bore, exclusive of the chamber, of the different mortars?

13-in., 26 inches; 10-in. sea-coast, 25 inches; 10-in. siege, 15 inches; 8-in., 12 inches; stone mortar, 19.8 inches; coehorn, 8.82 inches; eprouvette, 11.5 inches.

18. What is the length of the chamber of the different mortars?

13-in., 13 inches; 10-in. sea-coast, 10 inches; 10-in. siege, 5 inches; 8-in., 4 inches; stone mortar, 6.75 inches; coehorn, 4.25 inches; eprouvette, 1.35 inches.

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19. For what purpose is the eprouvette used?

For determining the relative strength of gunpowder.

20. To what purpose is a stone mortar applied?

To throw stones a short distance, from 150 to 250 yards; and also 6-pr. shells from 50 to 150 yards.

21. In what manner are the stones disposed in this mortar?

They are put into a basket fitted to the bore, and placed on a wooden bottom which covers the mouth of the chamber.

22. What use is made of coehorn mortars?

They are fired either from behind intrenchments like other mortars, or they may accompany troops in effecting lodgments in towns and fortified places.

23. What kind of projectiles are thrown from mortars?

Shells, fire-balls, carcasses, and stones.

24. How rapidly may siege mortars be fired?

At the rate of twelve rounds per hour continuously; and in case of need with greater rapidity.

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PART I. SECTION VI.

SEA-COAST ARTILLERY.

1. How are _Sea-Coast_ pieces mounted?

On barbette, casemate, flank-casemate, and columbiad carriages; and the carriage upon which the mortar is mounted—called its _bed_. These carriages do not subserve the purpose of transportation; the barbette carriage may, however, be used for moving its piece for short distances, as from one front of the work to another.

2. What number and kind of pieces are required for the armaments of forts on the sea-board?

In our service they are prescribed by the War Department, according to the character and extent of the work.

3. What disposition should be made of heavy and light pieces in a fortification?

Heavy pieces should be employed on the salients of the work, or for enfilading channels where a long range is required; light pieces, where the range is shorter.

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