THE HAND-BOOK OF
ARTILLERY.

BY CAPT. JOSEPH ROBERTS,

Fourth Regt. Artillery U. S. Army.

RICHMOND:
PRINTED BY RITCHIE & DUNNAVANT.
1861.

PROCEEDINGS.

The following Report was made by the Committee appointed at a meeting of the staff of the Artillery School at Fort Monroe, Va., to whom the commanding officer of the School had referred this work:

Your Committee to which has been referred the consideration of the work of Captain Roberts, proposed as a text-book for the Artillery School, beg leave to submit the following Report, viz:

The work submitted by Captain Roberts, and entitled “Hand-book of Artillery,” embraces sections on the following subjects.

[For subjects see [Table of Contents, page 7].]

Under each of these heads, except the last, the work contains a number of questions and answers. Your Committee have carefully examined each of these questions and their corresponding answers, and find that the answers have been principally drawn from the following sources, viz: Gibbon’s Artillerist’s Manual, Light and Heavy Artillery Tactics, and the Ordnance Manual, all of which works have been authorized by the War Department. Wherever the prescribed authorities furnish the means of answering the questions, they appear to have been followed as closely as possible.

The idea of the arrangement, and a few of the questions and answers, appear to have been taken from “Burns’ Questions and Answers on Artillery;” but that work has been so far deviated from, as fairly to entitle the present work to be considered as an original compilation.

In the opinion of your Committee, the arrangement of the subjects and the selection of the several questions and answers have been judicious. The work is one which may be advantageously used for reference by the officers, and is admirably adapted to the instruction of non-commissioned officers and privates of Artillery.

Your Committee do therefore recommend that it be substituted as a text-book in place of “Burns’ Questions and Answers on Artillery.”

(Signed) I. VOGDES,
Capt. 1st Art’y.

(Signed) E. O. C. ORD,
Capt. 3d Art’y.

(Signed) J. A. HASKIN,
Bvt. Maj. and Capt. 1st Art’y.

The preceding Report was adopted, and the Staff recommended this work as a book of instruction at the Artillery School, in lieu of “Burns’ Questions and Answers on Artillery.”

PREFACE.

The following compilation originated in an attempt to adapt Lieut. Col. Burns’ “Questions and Answers on Artillery” to the United States service. The British Artillery being very different from ours, it was found necessary to omit many of Burns’ questions, and to introduce others.

The compiler is under great obligations to several of his brother officers at Fort Monroe (especially to Major Haskin, 1st Artillery), for their kindness in assisting him in the compilation of this little volume, and for important suggestions in the revision of many of the “answers.”

Fort Monroe, Va., 1860.

CONTENTS.

The pages refer to the sidenotes in the margin of the text.

THE HAND-BOOK OF
ARTILLERY.

PART I. SECTION I.
ARTILLERY IN GENERAL.

9]

1. What is understood by the term Artillery?

Heavy fire-arms of every description.

2. How many kinds of Artillery are employed in the land service of the United States?

Four, viz.: Guns, Howitzers, Columbiads, and Mortars.

3. How are these pieces distinguished?

According to their use as Sea-coast, Garrison, Siege, and Field Artillery.

4. What metals are used in the construction of Artillery?

All heavy artillery, such as that for sea-coast, siege, and garrison equipment, is made of iron; and that for field service, of bronze.

10]

5. What is bronze for cannon?

An ALLOY consisting of 90 parts of copper and 10 of tin, allowing a variation of one part of tin more or less. It is commonly called brass.

6. Why is bronze used in preference to iron, for field pieces?

This metal, having greater tenacity and strength than iron, the pieces can be made lighter.

7. In what respect does iron merit a preference?

Iron is less expensive than bronze, and is more capable of sustaining long-continued firing with larger charges; such pieces are, therefore, better calculated for the constant heavy firing of sieges.

Note.—In the sieges in Spain, bronze guns could never support a heavier fire than 120 rounds in twenty-four hours, and were never used to batter at distances exceeding 300 yards; whereas, with iron guns, three times that number of rounds were fired with effect, from three times the distance, for several consecutive days, without any other injury than the enlargement of their vents. The comparative power of conducting heat in iron and copper being respectively as 3.743 to 8.932, taking gold at 10.000, it is evident that in practicing with iron and bronze pieces of the same calibre, it would soon become necessary to reduce the charges in the bronze pieces, and, also to increase the time between the discharges, to prevent their softening and drooping; while with iron, full charges and rapid firing may be kept up.

8. What additional objection has been urged to bronze for cannon?

The difficulty of forming a perfect alloy, in consequence of the difference of fusibility of tin and copper.

9. What iron pieces are used in the land service?

11]

12, 13, and 24-pdr. siege and garrison guns, 32 and 42-pdr. sea-coast guns, 8-in. siege and 24-pdr. garrison howitzers, 8 and 10-in. sea-coast howitzers, 8 and 10-in. columbiads, 8 and 10-in. siege, and 10 and 13-in. sea-coast mortars.

Note.—The 24-pdr. eprouvette is also of iron, and used for the proof of powder.

10. What are the kinds of bronze pieces in use at present?

6 and 12-pdr. field guns; 12-pdr. mountain howitzer; 12, 24 and 32-pdr. field howitzers; stone and 24-pdr. Coehorn mortars.

11. What is a battery?

This term is applied to one or more pieces, or to the place where they are served.

12. What regulate the dimensions of cannon?

The tenacity and elasticity of the metals employed in their fabrication. Their thickness must be proportioned to the effect developed by the powder; and the length is determined by experiment, and should not exceed 24 calibres. The exterior surface of a cannon is composed of several surfaces, more or less inclined to the axis of the bore, the forms of which have been determined by experiment.

13. Why is a piece made stronger near the breech than towards the muzzle?

Because the elastic force of the inflamed gunpowder is there greatest, constantly diminishing in intensity as the space increases in which it acts.

14. What is the length of a piece?

The distance from the rear of the base-ring to the face of the piece.

12]

15. What is the extreme length?

From the rear of the cascable to the face.

16. What is the bore of a piece?

It includes the part bored out, viz: the cylinder, the chamber (if there is one), and the conical or spherical surface connecting them.

17. What is understood by the calibre of a piece?

The diameter of the bore.

18. How do you ascertain the number of calibres in a piece?

Divide the length of the cylinder, in inches, by the number of inches in the calibre.

19. The number of calibres being known, how do you find the length of the cylinder?

Multiply the number of calibres by the calibre in inches.

20. What is meant by the sights of a piece?

Artificial marks on the piece for determining the line of fire.

21. How are the sights determined?

Usually by means of the gunner’s level, when the trunnions are perfectly horizontal.

22. What is the line of metal or the natural line of sight?

It is a line drawn from the highest point of the base-ring to the highest point on the swell of the muzzle.

23. What is the axis of a piece?

An imaginary line passing through the centre of the bore.

24. What is the natural angle of sight?

It is the angle which the natural line of sight makes with the axis of the piece.

13]

25. What is the dispart of a piece?

It is the difference of the semi-diameter of the base-ring and the swell of the muzzle, or the muzzle-band. It is, therefore, the tangent of the natural angle of sight to a radius equal to the distance from the rear of the base-ring to the highest point of the swell of the muzzle, or the front of the muzzle-band, as the case may be, measured parallel to the axis.

26. Give the nomenclature of a piece?

The CASCABLE is the part of the gun in rear of the base-ring, and is composed generally of the knob, the neck, the fillet, and the base of the breech.

The BASE OF THE BREECH is a frustum of a cone, or a spherical segment in rear of the breech.

The BASE-RING is a projecting band of metal adjoining the base of the breech, and connected with the body of the gun by a concave moulding.

The BREECH is the mass of solid metal behind the bottom of the bore, extending to the rear of the base-ring.

The REINFORCE is the thickest part of the body of the gun, in front of the breech; if there be more than one reinforce, that which is next the breech is called the first reinforce; the other the second reinforce.

The REINFORCE BAND is at the junction of the first and second reinforces in the heavy howitzers and columbiads.

The CHASE is the conical part of the gun in front of the reinforce.

The ASTRAGAL AND FILLETS in field guns, and the chase ring in other pieces, are the mouldings at the front end of the chase.

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The NECK is the smallest part of the piece in front of the astragal or the chase ring.

The SWELL OF THE MUZZLE is the largest part of gun in front of the neck. It is terminated by the muzzle mouldings, which in field and siege guns, consist of the lip and fillet. In sea-coast guns and heavy howitzers and columbiads, there is no fillet. In field and siege howitzers, and in mortars, a muzzle-band takes the place of the swell of the muzzle.

The FACE of the piece is the terminating plane perpendicular to the axis of the bore.

The TRUNNIONS are cylinders, the axes of which are in a line perpendicular to the axis of the bore, and in the same plane with that axis.

The RIMBASES are short cylinders uniting the trunnions with the body of the gun. The ends of the rimbases, or the shoulders of the trunnions, are planes perpendicular to the axis of the trunnions.

The BORE of the piece includes all the part bored out, viz.: the cylinder, the chamber (if there is one), and the conical or spherical surface connecting them.

The CHAMBER in howitzers, columbiads, and mortars, is the smallest part of the bore, and contains the charge of powder. In the howitzers and columbiads,[1] the chamber is cylindrical; and is united with the large cylinder of the bore by a conical surface; the angles of intersection of this conical surface with the cylinders of the bore and chamber, are rounded (in profile) by arcs of circles. In the 8-inch siege howitzer, the chamber is united with the cylinder of the bore by a Spherical surface, in order that the shell may when necessary, be inserted without a sabot.

15]

The BOTTOM OF THE BORE (to facilitate sponging) is a plane perpendicular to the axis, united with the sides (in profile) by an arc of a circle the radius of which is one-fourth of the diameter of the bore at the bottom. In the columbiads, the heavy sea-coast mortars, stone mortar, and eprouvette, the bottom of the bore is hemispherical.

The MUZZLE, or mouth of the bore, is chamfered to a depth of 0.15 inch to 0.5 inch (varying with the size of the bore), in order to prevent abrasion, and to facilitate loading.

The TRUE WINDAGE is the difference between the true diameters of the bore and of the ball.

27. What is the vent?

The aperture through which fire is communicated to the charge.

28. What is to be observed in reference to the diameter of the vent?

It should be as small as the use of the priming wire and tube will allow.

29. Why?

As the velocity of the gases arising from the combustion of the powder is extremely great, a large amount escapes through the vent, which contributes nothing to the velocity of the projectile. It therefore follows, that the effect produced by a given charge will diminish as the diameter of the vent increases. Besides, on account of the increase of power in the current that escapes from them, large vents are more rapidly injured than small ones.

16]

30. What is the diameter of the vent?

0.2 of an inch in all pieces except the eprouvette, in which it is 0.1.

31. What is the position of the axis of the vent?

The axis of the vent, is in a plane passing through the axis of the bore, perpendicular to the axis of the trunnions. In guns, and in howitzers having cylindrical chambers, the vent is placed at an angle of 80° with the axis of the bore, and it enters the bore at a distance from the bottom equal to one-fourth the diameter of the bore. As this inclination renders it easy to pull the friction tube out of the vent, that of the new 12-pdr. field gun, and the new columbiads has been placed perpendicular to the axis.

32. What are the quarter-sights of a piece?

Divisions marked on the upper quarters of the base ring, commencing where it would be intersected by a plane parallel to the axis of the piece, and tangent to the upper surface of the trunnions.

Note.—Not used in our service.

33. To what use are the quarter-sights applied?

For giving elevations up to three degrees but especially for pointing a piece at a less elevation than the natural angle of sight.

34. What is a breech-sight?

An instrument having a graduated scale of tangents, by means of which any elevation may be given to a piece.

17]

35. How are the divisions of the tangent scale found?

By taking the length of the piece, from the rear of the base-ring to the swell of the muzzle, measured on a line parallel to the axis, and multiplying it by the natural tangent of as many degrees as may be required; and then deduct the dispart. Thus, for 5° elevation, and the gun supposed to be 5 feet, or 60 inches long, multiply .08748, which is the natural tangent of 5°, by 60; the product gives 5.2488 inches; supposing the dispart to be 1 inch, the graduating of the tangent scale will be 4.2488 inches.

36. With what pieces are breech-sights used?

Guns and howitzers.

37. What is a pendulum hausse?

It is a tangent scale, the graduations of which are the tangents of each quarter of a degree of elevation, to a radius equal to the distance between the muzzle-sight of the piece, and the axis of vibration of the hausse, which is one inch in rear of the base-ring. At the lower end of the scale is a brass bulb filled with lead. The slider which marks the divisions on the scale is of thin brass, and is clamped at any desired division on the scale by means of a screw. The scale passes through a slit in a piece of steel, with which it is connected by a screw, forming a pivot on which the scale can vibrate laterally. This piece of steel terminates in pivots, by means of which the pendulum is supported on the seat attached to the gun, and is at liberty to vibrate in the direction of the axis of the piece. The seat is of metal, and is fastened to the base of the breech by screws, so that the centres of the steel pivots of vibration shall be at a distance from the axis of the piece equal to the radius of the base-ring.

18]

A MUZZLE-SIGHT of iron is screwed into the swell of the muzzle of guns, or into the middle of the muzzle-ring of howitzers. The height of this sight is equal to the dispart of the piece, so that a line joining the muzzle-sight and the pivot of the tangent scale is parallel to the axis of the piece.

38. What is a gunner’s level, or gunner’s perpendicular?

An instrument made of sheet-brass; the lower part is cut in the form of a crescent, the points of which are made of steel; a small spirit-level is fastened to one side of the plate, parallel to the line joining the points of the crescent, and a slider is fastened to the same side of the plate, perpendicular to the axis of the level.

39. What is it used for?

To mark the points of sight on pieces.

40. What is a plummet?

A simple line and bob for pointing mortars.

41. What is a gunner’s quadrant?

It is a graduated quarter of a circle of sheet-brass, attached to a brass rule 18 inches long. It has a vernier turning on a pivot, to which is attached a spirit-level. To get a required elevation, the vernier is fixed at the indicated degree, the brass rule is then inserted in the bore parallel to the axis of the piece; the gun is then elevated or depressed until the level is horizontal.

There is another graduated quadrant of wood, of 6 inches radius, attached to a rule 23.5 inches long. It has a plumb-line and bob, which are carried, when not in use, in a hole in the end of the rule, covered by a brass plate.

19]

42. What is an elevating arc, and its use?

It is an arc attached to the rear part of the cheek of a gun-carriage, having its centre in the axis of the trunnions; the arc is graduated into degrees and parts of a degree. By placing the axis of the piece horizontal, and marking the breech at any one of the divisions on the arc, any elevation or depression required will be noted by the number of degrees below or above this mark. It turns on a pivot which admits of the arc, when not in use, being placed inside the cheek to which it is attached.

43. What is the use of the knob of the cascable?

To facilitate the handling of the piece in mounting and dismounting it, and moving it when off its carriage.

44. Of what use are the trunnions of a piece?

By means of them the piece is attached to its carriage; and by being placed near the centre of gravity, it is easily elevated or depressed.

45. What are the dolphins of a piece?

Two handles placed upon the piece with their centres over the centre of gravity, by which it is mounted or dismounted.

46. Are all pieces provided with dolphins?

Only the 12-pdr. brass guns, and the 24 and 32-pdr. brass howitzers.

47. What is understood by the preponderance of a piece?

It is the excess of weight of the part in rear of the trunnions over that in front; it is measured by the weight which it is necessary to apply in the plane of the muzzle to balance the gun when suspended freely on the axis of the trunnions.

48. Why is this preponderance given?

To prevent the sudden dipping of the muzzle, in firing, and violent concussion on the carriage at the breech.

20]

49. What is bushing a piece of artillery?

Inserting a piece of metal about an inch in diameter (near the bottom of the bore), through the centre of which the vent has been previously drilled. It is screwed in.

50. What kind of metal is used for bushing bronze pieces?

Pure copper always, which is not so liable to run from heat as gun metal.

51. What is the object of bushing a piece?

To prevent deterioration of the vent, or provide a new one when this has already occurred.

52. Is all new artillery bushed?

No, only bronze pieces, and iron pieces, only when repeated firing has rendered it absolutely necessary.

53. How is artillery rendered unserviceable?

I. Drive into the vent a jagged and hardened steel spike with a soft point, or a nail without a head; break it off flush with the outer surface, and clinch the point inside by means of the rammer.

II. Wedge a shot in the bottom of the bore by wrapping it with felt, or by means of iron wedges, using the rammer or a bar of iron to drive them in.

III. Cause shells to burst in the bore of bronze guns.

IV. Fire broken shot from them with large charges.

V. Fill the piece with sand over the charge, to burst it.

VI. Fire a piece against another, muzzle to muzzle, or the muzzle of one to the chase of the other.

VII. Light a fire under the chase of a bronze gun, and strike on it with a sledge, to bend it.

VIII. Break off the trunnions of iron guns; or burst them by firing them at a high elevation, with heavy charges and full of shot.

21]

54. State how to unspike a piece.

If the spike is not screwed in or clinched, and the bore is not impeded, put in a charge of powder ⅓ of the weight of the shot, and ram junk wads over it; laying on the bottom of the bore a slip of wood, with a groove on the under side containing a strand of quick-match, by which fire is communicated to the charge. In a brass gun, take out some of the metal at the upper orifice of the vent, and pour sulphuric acid into the groove, and let it stand some hours before firing. If this method, several times repeated, is not successful, unscrew the vent piece if it be a brass gun; and if an iron one, drill out the spike, or drill a new vent.

55. Explain how to drive out a shot wedged in the bore.

Unscrew the vent piece, if there be one, and drive in wedges so as to start the shot forward; then ram it back again in order to seize the wedge with a hook; or pour in powder, and fire it after replacing the vent piece. In the last resort, bore a hole in the bottom of the breech, drive out the shot, and stop the hole with a screw.

56. What is scaling a piece of artillery?

Flashing off a small quantity of powder to clean out the bore; about 1-12 of the shot’s weight. The practice is discontinued.

22]

57. How are cannon in our service marked?

As follows, viz: The number of the gun and the initials of the inspector’s name on the face of the muzzle,—the numbers in a separate series for each kind and calibre at each foundry; the initial letters of the name of the founder, and of the foundry, on the end of the right trunnion; the year of the fabrication on the end of the left trunnion; the foundry number on the end of the right rimbase, above the trunnion; the weight of the piece in pounds on the base of the breech; the letters U. S. on the upper surface of the piece, near the end of the reinforce.

58. What marks are used to designate condemned pieces?

Pieces rejected on inspection are marked X C on the face of the muzzle; if condemned for erroneous dimensions which cannot be remedied, add X D; if by powder proof, X P; if by water proof, X W.

59. What are the kinds of proof which artillery must undergo, before being received into the service?

1st. They are gauged as to their several dimensions, internal and external; as to justness and position of the bore, the chamber, vent, trunnions, &c.

2d. They are fired with a regulated charge of powder and shot, being afterwards searched to discover irregularities or holes produced by the firing.

3d. By means of engines, an endeavor is made to force water through them.

4th. They are examined internally, by means of light reflected from a mirror.

23]

60. Are brass cannon liable to external injury, caused by service?

They are little subject to such injury, except from the bending of the trunnions sometimes, after long service or heavy charges.

Note.—Recent experiments at Fort Monroe show that brass guns, when rifled, and fired with large charges and heavy shot, expand so much that the projectile does not take the grooves.

61. What are the causes of internal injury?

Internal injuries are caused by the action of the elastic fluids developed in the combustion of the powder, or by the action of the shot in passing out of the bore.

62. Name the injuries of the first kind.

Enlargement of the bore by the compression of the metal; corrosion of the metal at the inner orifice of the vent, or at the mouth of the cylindrical chamber; cracks, from the yielding of the cohesion of the metal; cavities, cracks enlarged by the action of the gas, and by the melting of the metal, observable especially in the upper surface of the bore.

63. Name those of the second kind.

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The lodgment of the shot,—a compression of the metal on the lower side of the bore, at the seat of the shot, which is caused by the pressure of the gas in escaping over the top of the shot. There is a corresponding burr in front of the lodgment; and the motion thereby given to the shot causes it to strike alternately on the top and bottom of the bore, producing other enlargements, generally three in number: the first, on the upper side a little in advance of the trunnions; the second, on the lower side about the astragal; the third, in the upper part of the muzzle; it is chiefly from this cause that brass guns become unserviceable. Scratches, caused by the fragments of a broken shot, or the roughness of an imperfect one; enlargement of the muzzle by the striking of the shot in leaving the bore; external cracks, or longitudinal slits, caused by too great a compression of the metal on the inside.

64. When is a piece said to be honeycombed?

When the surface of the bore is full of small holes or cavities.

65. To what is this due?

To the melting and volatilization of a portion of the tin in the alloy; tin being much more fusible than copper.

66. Do lodgments cause an inaccuracy of fire?

They do.

67. How may this in a measure be remedied?

By using a wad over the cartridge, in order to change the place of the shot; or by wrapping the shot in woollen cloth or paper, so as to diminish the windage. In field guns, the paper cap which is taken off the cartridge should always be put over the shot.

68. To what injuries are iron cannon subject?

To the above defects in a less degree than brass, except the corrosion of the metal, by which the vent is rendered unserviceable from enlargement. The principal cause of injury to iron cannon is the rusting of the metal, producing a roughness and enlargement of the bore, and an increase of any cavities or honeycombs which may exist in the metal.

69. How may you judge of the service of an iron gun?

Generally by the appearance of the vent.

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70. What rules are laid down for the preservation of artillery?

Cannon should be placed together, according to kind and calibre, on skids of stone, iron, or wood, laid on hard ground well rammed and covered with a layer of cinders or of some other material to prevent vegetation. In case of guns and long howitzers, the pieces should rest on the skids in front of the base ring and in rear of the astragal, the axis inclined at an angle of 4° or 5° with the horizon, the muzzle lowest, the trunnions touching each other; or the trunnion of one piece may rest on the adjoining piece, so that the axis of the trunnions may be inclined about 45° to the horizon; the vent down, stopped with a greased wooden plug, or with putty or tallow. The pieces may be piled in two tiers, with skids placed between them exactly over those which rest on the ground; the muzzles of both tiers in the same direction and their axes preserving the same inclination. In case of short howitzers and mortars, the pieces should stand on their muzzles, resting on thick planks, the trunnions touching, the vents stopped.

71. What additional precautions should be observed in case of iron pieces?

They should be covered on the exterior with a lacker impervious to water; the bore and the vent should be greased with a mixture of oil and tallow, or of tallow and beeswax melted together and boiled to expel the water. The lacker should be renewed as often as necessary, and the grease at least once a year. The lacker and grease should be applied in hot weather. The cannon should be frequently inspected, to see that moisture does not collect in the bore.

26]

PART I. SECTION II.
ON GUNS.

1. What are Guns?

Long cannon without chambers.

2. How are guns denominated?

By the weight of their respective shot.

3. What are the principal parts of a gun?

The cascable, breech, reinforce, chase, and muzzle.

4. What proportion usually exists between the length and calibre of a gun?

It varies from 15 to 23 calibres.

5. What proportion does the dispart of a gun bear generally to its length?

About a sixtieth part in field guns, about a thirtieth part in sea-coast, and about a thirty-eighth part in siege and garrison guns.

6. What is the natural angle of sight in siege and garrison guns?

One degree and thirty minutes.

7. What is it in field guns?

One degree.

8. Why have sea-coast guns no natural line of sight?

Because the swell of the muzzle is not visible when the eye is on a level with the base ring.

9. Upon what are guns mounted?

On field, siege, barbette or casemate carriages.

27]

10. What projectiles are used with guns?

Solid shot, spherical case, grape, and canister.

11. About what are the weights of the different guns?

6-pdr., 884 lbs.; brass 12-pdr., 1,757 lbs.; iron 12-pdr., 3,590 lbs.; 18-pdr., 4,913 lbs.; 24-pdr., 5,790 lbs.; 32-pdr., 7,200 lbs.; 42-pdr., 8,465 lbs.

12. Give the entire length of the several guns?

6-pdr. field-gun, 65.6 inches; 12-pdr. field-gun, 85 inches; 12-pdr. iron gun, 116 inches; 18-pdr., 123.25 inches; 24-pdr., 124 inches; 32-pdr., 125.2 inches; 42-pdr., 129 inches.

28]

PART I. SECTION III.
ON HOWITZERS.

1. What is a Howitzer?

A chambered piece, of larger calibre than a gun of like weight, and mounted in a similar manner.

2. What form of chamber is given to howitzers?

That of a cylinder.

3. How is it united with the large cylinder of the bore?

By a conical surface, except in the 8-inch siege howitzer, where it is united with the cylinder of the bore by a spherical surface, in order that the shell may—when necessary—be inserted without a sabot.

4. What advantages are gained by the employment of howitzers?

They project larger shells than the guns with which they are associated, are well adapted for ricochet fire, the destruction of field works, breaking down palisades, and setting fire to buildings.

5. What projectiles are used with howitzers?

Shells usually, spherical case, canister, grape and carcasses.

29]

6. Give the entire length of the several howitzers.

Iron 10-inch, 124.25 inches; 8-inch sea-coast, 109 inches; 8-inch siege and garrison, 61.5 inches; 24-pdr. garrison, 69 inches; 32-pdr. field, 82 inches; 24-pdr. field, 71.2 inches; 12-pdr. field, 58.6 inches; mountain, 12-pdr., 37.21 inches.

7. What is the weight of a howitzer of each kind?

10-inch, 9,500 lbs.; 8-inch sea-coast, 5,740 lbs.; 8-inch siege and garrison, 2,614 lbs.; 24-pdr. garrison, 1,476 lbs.; 32-pdr. field, 1,920 lbs.; 24-pdr. field, 1,318 lbs.; 12-pdr. field, 788 lbs.; 12 pdr. mountain, 220 lbs.

8. What is the natural angle of sight in siege and garrison and field howitzers?

One degree.

9. What in mountain howitzers?

Thirty-seven minutes.

10. Why have sea-coast howitzers no natural line of sight?

Because the swell of the muzzle is not visible when the eye is on a level with the base ring.

30]

PART I. SECTION IV.
ON COLUMBIADS.

1. What is a Columbiad?

A gun of much larger calibre than the ordinary gun, used for throwing solid shot or shells.

2. What are some of the peculiarities of this gun, when mounted in barbette?

Its carriage gives a vertical field of fire from 5° depression to 39° elevation; and a horizontal field of fire of 360°.

3. Are these pieces chambered?

Those of the old pattern have chambers; but they are now cast without any.

4. Give the weight of this piece?

10-inch, 15,400 lbs.; 8-inch, 9,240 lbs.

5. What is the entire length of this gun?

10-inch, 126 inches; 8-inch, 124 inches.

6. What is the natural angle of sight in this piece?

8-inch, 1° 23´; 10-inch, 1° 21´.

31]

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?