Chapter III: Part I: Section I

ARTILLERY IN GENERAL.

[Sidenote: 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.

[Sidenote: 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?

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 14]]

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.

[1] The new columbiad is made without a chamber.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 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.

[Sidenote: 24]]

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.

[Sidenote: 25]]

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.

[Sidenote: 26]]