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CHAPTER VIII.

PRACTICE OF FIRE.

In the fire of any kind of arm, the probability of striking a mark is so much the greater as the calibre increases, as the trajectory is less inflected, and as the dimensions of the object fired at exceed the extent of the variations observed in several successive shots fired as nearly as possible under the same circumstances. When the difference between these variations exceeds the dimensions of the object, the probability of striking it becomes very slight.

Two kinds of variations occur-- one laterally, the other in the direction of the range. The last is of the most importance, for the object generally is to strike within limits extending horizontally snore than vertically. The limits in the last direction being 5 feet 5 inches, or 8 feet 4 inches, according as the fire is against foot troops or cavalry.

As the angle of fire increases, the variations in range decrease up to the angle of greatest range, at which the variations are the least possible, fur the kind of piece and charge used.  Therefore, the angle of greatest range is the most advantageous in practice, when the object is to plant the greatest number of balls within a given space.

The angle of greatest range would be in vacuo 45º. Practically, it is a little less when firing mortars, but with larger pieces it is between 28 º and 35º. The fire of the ordinary musket is uncertain beyond 200 yards, the variations in height, from one shot to another, at that distance, often exceed one or one and a half yards. But when troops are in compact masses, the fire is still very effective beyond that distance. At 650 yard's the musket bullet is still deadly, and instances have been known where men have been killed or wounded at greater distances. In general, the infantry soldier, in the excitement of battle, does not make full use of the accuracy of fire of his arm, which has led some to think there is no great advantage in perfecting the accuracy of fire of arms intended for the use of the mass of troops. But this is evidently a mistake, since out of a, number of shots fired frown any two pieces, that one which is the most accurate, will have the greatest number effective. So long as the fact remains of the great disparity between the number of balls expended and the number which proves effective, it is useless to give the men the means of firing a greater number of balls in a given time. It is, therefore, not advisable to arm our infantry with breech-loading arms, which, enabling them to expend the limited amount of ammunition carried on the person, in one-third or one-fourth the usual time, leaves them destitute perhaps at the most critical monument. The best position for such an ann is in the hands of superior marksmen, detached as light infantry, or in deliberate firing from behind obstacles of some kind.

The effective range of the rifled spherical bullet, is over 400 yards. The oblong rifle-bullet is effective at 1,000 yards; but these arms exhibit their marked superiority when used. By isolated marksmen.

Cavalry fire is generally of but little effect; though some examples of its efficiency have been exhibited, especially during the Peninsular war.

Solid Shot .-- Beyond the limit of distinct vision, all fires become inexact; and infantry should not be added at by fieldpieces beyond 1,000 yards, nor cavalry beyond 1,200, unless the ground is suitable for ricochet firing, and the enemy's troops are in dense masses

The precise effect of a, single ball cannot be accurately stated. Cases are cited where thirty or forty men have been disabled by a single shot; but it is laid down as a principle, that a 6 or 12 pound ball will go through six men at 800 yards distance.

As the distance decreases, the 12-pounder loses some of its advantage over the 6-pounder; but it is always superior in its five, and experiments show that the larger calibre may compensate, by its greater accuracy, for the less number of its shots.

On hard, dry ground, the rolling is better than the direct fire, at very great distances, as then the shot bounds along the ground, striking objects at a number of points on its trajectory. On favorable ground, solid shot from field-guns will range as high as 1,600 or 1,800 yds. The probability of striking an object is the greatest possible at 500 yards, at which distance two-thirds or one-half of the balls will hit. At 800 yards, the chance of striking an object is reduced to one-third or one-fourth.

If a ball, moving with great velocity, goes through an object which offers little resistance, it does not displace it, and will make but a small hole; but if the ball has but little velocity, it splits and scatters the object into splinters.

A ball, passing through any of the fir-woods, makes a clean round hole, while oak is splintered and broken to a more or less extent. In this respect the former is, then, preferable to oak in positions exposed to the fire of artillery.

Solid shot is of very little effect upon earthen parapets, unless it passes through, in which case it soon knocks them down. At 600 yards, shot from field-guns will penetrate from 5 to 6 ½ feet into newly thrown-up earth. Siege-guns will penetrate with their shot double this distance.

Shells, although less accurate than solid shot, produce a greater moral effect by their noise and force of explosion. They are, therefore, to be preferred in firing against cavalry, and are used also to reach troops backed by broken ground, or works, and to set fire to block-houses or villages, held by an enemy, and in general, against any wooden structure, which they break up and set fire to.

The large 8-in. and 10-in. howitzer-shells are very destructive either by destroying or setting fire to the shelters of an enemy, or by destroying the parapets and traverses of his batteries, the shells acting, in their explosion, like small mines.

When a shell is burst while stationary, the pieces are dispersed in almost every direction, with more or less force, according to the resistance offered by the sides. But if it is in motion, those parts of it in front will move forwards with an increased, and those in rear  with a decreased velocity; and in case the shell is moving at the time with very little velocity, this may be entirely overcome for the rear parts by the explosion, and they may drop at once to the ground, or even be thrown backwards.

Trajectory .-- Very little was known in early times of the form of the path described by a projectile moving through the air; it being supposed by some a compound curve, and by others a parabola with a vertical axis; and these errors continued until Sir Isaac Newton, towards 1723, demonstrated the modifications produced by the resistance of the air, which he estimated was proportional to the square of the velocity; and Benjamin Robins, the inventor of the ballistic pendulum, showed conclusively that the resistance of the air could not be neglected in computing the trajectory, by proving the range in vacuo many times greater than that in the air.

On horizontal ground the descending branch is always the shortest. The angle of fire is the angle TAC, which the axis makes with the horizontal. When the gun and point of fall are on the same level, this angle is less than the angle of fall, which is the angle BCA made by the tangent to the trajectory with the ground at the point of fall.

As the weight of a projectile increases, and its velocity decreases, the resistance of the air decreases, the curve described becomes more like a parabola, and the angle of fall becomes more nearly equal to the angle of fire.

Ricochets .- When the angle of fall is small enough, the projectile rises and continues to move on, forming a series of bounds or ricochets, increasing in number as the angle of incidence de creases, the velocity increases, and the ground is snore elastic and resisting.

The projectile will ricochet under a greater angle on a hard resisting soil, than it will on a soft one. A ricocheting ball makes a furrow in the ground, and each time the angle under which it leaves the ground is greater than that under which it enters it; for, having lost a portion of its velocity in passing over the first part of the curve, it has no longer the same power to overcome resistance, and must pass out by a shorter path than the one it followed in entering, and consequently the angle is increased, which causes the more or less rapid extinction of the ricochets.

An incompressible surface, like water, is still more favorable for ricochets than ground, and is attended, besides, with less loss of velocity. If the angle of incidence is too great, the ball buries itself in the ground, inclining to the side on which it meets with least resistance.

The kind of fire varies with the ground and the object to be attained.

A direct fire is one in which the projectile strikes the mark without touching the intermediate ground. This fire is generally used with guns.

A grazing fire is where the ball, rising but slightly from the ground, and striking it under a small angle, makes, at the end of its flight, a large number of ricochets. In such a fire, the ball should not strike the ground under a greater angle than 10º.

A plunging fire is where a ball, striking under a large angle, buries itself in the ground, losing its velocity entirely, or making only a few ricochets. The least angle under which this takes place is about 10 º.

A horizontal, parallel, or rolling fire, is one in which the axis of field-pieces is placed horizontal or parallel to the ground. In this case, the line of sight strikes the ground about 75 yards in front of the piece, and the ball meeting it under a very small angle, describes a number of low bounds or ricochets. This kind of fire is more efficient in striking a remote line than the direct fire, as the ball in the latter, rising higher, can strike an enemy in only a very small segment of its path. For the horizontal fire, however, a very hard, arm, and level ground is required, such as is very seldom met with on a field of battle.

A ricochet fire is used to strike an enemy concealed behind an obstacle, and to break up the ground he occupies, by the successive ricochets of the shot. It is used, especially in sieges, in flank and reverse fires, to destroy the defenses of the besieged, and dismount his guns. The ball having grazed the interior crest of the parapet adjoining the face to be destroyed, falls upon the terreplein and ricochets along it.

The angle of arrival is the angle which the tangent to the trajectory makes with the horizontal at the interior crest; while the angle of fall is the angle which the tangent makes at the point of fall with the terreplein.

The size of this angle will determine the kind of ricochet. It will be grazing if the angle is 4ºor less, and plunging when it is comprised between 6º and 10º.

Small projectiles seldom ricochet under angles so large as from 7º to 8º. Large shells ricochet under greater angles than large shot.

At great distances, either can be employed, but the grazing is generally used as more efficacious; though the trajectory must have a certain degree of curvature, otherwise many of the shot are lost by passing over the work.

As the projectile should strike the terreplein as near as possible to the interior crest, it should pass over this on the descending branch of its trajectory; otherwise, continuing to rise, it would pass over the work entirely, or partly, and strike objects only on a small segment of its path, so that at very short distances a more erected curve is necessary.

Upon terrepleins the limit of ricochets seldom exceeds 10º unless the ground is very dry and hard. A ball will ricochet better in dry summer weather than in wet.

In grazing ricochets, the ball is given a great velocity, and the curves described are long and flat. In plunging ricochets the contrary is the case.

Solid shot, acting by their force of percussion alone, are not very effective when they have but little velocity. Guns, therefore, should not be employed under 200 yards, as it would be necessary to decrease the charges too much for ricochet firing. Howitzers can be used advantageously at the shortest distances; the size of the shells and their force of explosion supplying their want of velocity.

The ricochet firing with field-pieces differs but little from a rolling fire; when this fire is used against works, it resembles that used in the attack of fortifications.

The fire of the greatest range, is that obtained by giving the piece the greatest elevation it can take on its carriage, and employing the largest charge used for that calibre; but as this kind of fire is very injurious to the carriage, and often breaks it, it is employed only in testing.

Horizontal fires, are those in which the axis of the piece has small angles of elevation.

Vertical fires, are those where the angle is very great, as in mortars.

The rules of fire for ordnance which fires horizontally, result from the knowledge of the

mean trajectory, which, like the mean trajectory of the musket, comprises all the causes of error which can modify the fire; but the trajectory of artillery projectiles being more constant in its form, the results are more accurate, a consequence of the fact that as the calibre of the arm increases, each particular trajectory approaches more nearly the mean trajectory.

When canister is fired, the balls, having broken the case, escape in the form of a cone,  and striking against each other, and against the sides of the piece, diverge more or less according to the distance; but the greater part of the balls are found to be near the centre, and the rules of fire are still based upon. the knowledge of the mean trajectory.

For vertical fires, the rules are based upon the knowledge of the mean range, and the relation which can be established between charges and the corresponding ranges.

The ranges of pieces of the same calibre, fired under the same angle and with the same charge, will be different from various causes, among which are--

The different diameters of the bore and vent, from the widening of these parts.

The difference in the diameter and weight of the projectiles. The difference in the quality of the powder, and especially in its hygrometric state, and the manner in which it inflames and communicates motion to the projectile.

The thermometric, barometric, and hygrometric state of the air; a variation in the temperature and pressure, increasing or diminishing sensibly the range.

The vibrations of the piece and the projectiles, especially when the latter are hollow, are not without their influence, particularly when the piece is formed of a thin and elastic tube; and it is from this last reason that pieces whose recoil has been almost entirely prevented, fire less accurately than those which are allowed to recoil freely. The vibrations are so much the more violent as the charge and length of piece are increased; and experiment proves that a musket fires less accurately when solidly fixed, than when fired from the shoulder.

Loading.-- The manner of loading the different kinds of pieces being given in the tactics, it will be necessary here simply to lay down some general principles.

In long pieces, the vent should always be kept carefully closed, while the sponging is going on, to prevent the current of air from passing out and collecting there pieces of thread, paper, &c., from the cartridge-bag, which would retain fire in the gun, and cause premature explosion the next time the gun was loaded. This precaution is the more necessary, when the sponge fits the bore tight, and acts as a piston. The sponge should be well pressed down against the bottom of the bore, and turned, so as to leave no remnant of the cartridge-bag. In mortars, where a sponge is seldom used, or when it does not fit tightly, the stopping of the vent is not necessary; but it should always be cleared out with the priming-wire before the powder is placed in. Mortar-shells should be let down gently so as not to be forced into the chamber, or crush suddenly any powder they may meet.

The use of sabots is avoided when firing over the heads of oar own men.

Sometimes, instead of using a sabot, the shell is prevented from turning in the bore by having attached to it a ring or grommet wad. Shells should not be rammed, but pushed gently home with the rammer.

The 8-in. siege-howitzer, being loaded by hand, the fuze can be placed in- its proper position without the assistance of a sabot, which, when the piece was fired in the trenches over the heads of the working parties, would be dangerous to them.

In loading this piece, as well as with the mortars, care should be taken that no powder remains along the bore; and in firing under small angles, or at a depression, the shell should be wedged up, to prevent its rolling out.

In the stone-mortar, the month of the chamber is covered with a thick oak plank having a, number of holes bored through it, to allow the passage of the flame; and when shells are fired, they are laid in beds with their fuzes placed outwards, and cut to burn 15 seconds. The mortar is primed with a piece of quick-match long enough to allow the cannoneers to get out of the way of any fragments which might fall in the battery. The same precaution is not necessary when stories or balls are fired, though the mortar is then given an elevation of 60ºinstead of 30º. If the charge is too great, the projectiles are disseminated over too great a space. It should not exceed 1 ½ lb. with a weight of projectile of 100 lbs. It may sometimes become necessary to fire a shell from a mortar too large for it; in which case it is wedged in on different sizes with pieces of soft wood and the space between it and the bore filled in with earth.

Large shells may be fired from guns or howitzers by placing the breech in n, hole 2 or 3 feet, deep, and resting the piece length ways on two pieces of timber, inclined about 45º, the elevation being regulated by a quoin under the chase. The shell is then placed upon the month of the piece, and held there by a, cord, which passes around it and is fastened to one around the neck. In this way the shell closes the mouth of the piece. The loading is as easily and as quickly performed as in mortars, and the firing is tolerably accurate. To insure the fuze taking fire, it is primed with a piece of quick-match.

Care should be taken in loading to put the seam of the cartridge to the sides, so that it will not come under the vent. In loading the 32 and 24-pdr. howitzer, the cartridge is first  pushed carefully into the chamber without ramming, and the shell is than set home, also without ramming.

In loading the mountain-howitzer, it is best to keep the sponge moistene d, especially when the piece is fired rapidly.

For want of shells to set fire to works in the field, hot shot may be used, the forge serving as a furnace to heat them in. Canister shot may be replaced by filling pasteboard cylinders, having heads of elm, 1 ½ inch thick-, with musket-bullets placed in beds, and sealed with good plaster; the weight of the whole not to exceed that of the shot, and to be fired with the charge of one-fifth of that weight, and not at a greater range than 300 or 400 yards.

Charges- The charges to be used depend upon the kind of fire, the purpose of it, the nature of the ground, object fired at, &c.

In mortars, the usual angle of elevation is 45º, generally a little less; and the charges vary according to the distances. The charges are rectified by knowing the increased range corresponding to a given increase in charge.

In early times two men were required in firing a mortar, one to fire the piece, the other to light the fuze, which could not take fire from the blast, earth being packed in to destroy the windage, and with an idea that it prevented the shell from being broken. This method of firing gave rise to many accidents. Should the piece, miss fire, the shell burst in it, and if the fuze failed to take fire before the charge, it did not burst at all. As soon as it became known that the fuze could be lit by the blast of the charge, the packing of earth. was discontinued, and the present method of firing was adopted.

Long pieces were at first loaded with loose powder, carried to its place at the bottom of the bore by means of a long-handled ladle; and although cartridge bags were sometimes used, it was not until Gribeauval substituted the use of them entirely that they were permanently adopted. To this celebrated Frenchman are we also indebted for the use of the hausse, or breech-sight, previously almost entirely unknown. Before its adoption, pieces were fired with but little accuracy, except at point-blank range; and it is singular that so many objections should have been urged against the use of an instrument now so indispensable to the proper sighting of artillery.

In field-guns, when firing solid shot, the charge is usually about one-fifth the weight of the shot.* For spherical ease and canister, the charge is less. These projectiles are always fixed to a block of wood, called a sabot (fig. 165) to which the cartridge is also attached; forming what is called a round of fixed ammunition. Fig. 166.

* In the new 12-pdr. gun the charges for all kinds of projectiles are the same, 2 ½ lbs.

In the 12-pdr. field-howitzer, also, the ammunition used is fixed, A, Fig. 164; but with the other howitzers the projectile and charge are separate, the latter being attached to a block of wood called a, cartridge-block, Fig. 166, the object of which is to give a finish to the cartridge and fill the chamber, the dimensions of the block being so calculated for each different charge as to reach to the mouth of the chamber. The sabots used with these heavy howitzers are conical in shape to fit the connecting surface between the chamber and bore.

For the siege and garrison-guns, the charge is one-fourth the weight of the shot, which is increased in breeching to one-third, and sometimes to one-half. The French, whose guns of this size are made of bronze, use hay-wads between the charge and shot, varying the length of wad so as to prevent the formation of lodgments in the bore. Wads are not usually employed in our service. For firing hot shot, cartridge-bags are made double, by placing one within the other, care being taken to prevent the powder sifting out; and wads of wet hay or  clay are used.

To load with hot shot .-- The piece should be sponged with great care, and the worm frequently passed into the bore. As a precaution, it is well to insert a wet sponge just before putting in the ball.

The muzzle being sufficiently elevated to allow the ball to roll down the bore, the cartridge is inserted, the mouth of the outer bag foremost, the fold down, and carefully pushed home without breaking it; a dry hay wad is placed upon it and rammed once; then a clay or wet hay wad and rammed twice; and finally, if firing at angles of depression, a wad of clay a half-calibre in length, or a wet hay wad, is put on the ball.

The charges for hot shot are from one-fourth to one-sixth the weight of the shot. With small velocities, the shot splits and splinters the wood, so as to render it favorable for burning. With great velocity, the ball sinks deep into the wood, is deprived of air by the closing of the hole, and chars instead of burning the surrounding wood. It should not penetrate deeper than 10 or 12 inches. Red-hot balls do not set fire to the wood until some time after their penetration. They retain sufficient heat to ignite wood after having made several ricochets upon water.

The wads are made of clay or hay. Clay wads should consist of pure clay, or fuller's earth, free from sand or gravel, well kneaded with just enough moisture to work well. They are cylindrical, and one calibre in length.

Hay walls should remain in the tub to soak at least ten or fifteen minutes. Before being used, the water is pressed out of them.

When hay wads are used, vapor may be seen escaping from the vent on the insertion of the ball; but as this is only the effect of the heat of the ball on the water contained in the wad, no danger need be apprehended from it.

With proper precautions in loading, the ball may be permitted to cool in the gun without igniting the charge. The piece, however, should be fired with as little delay as possible, as the vapor would diminish the strength of the powder.

Furnaces for heating shot are erected at the forts on the sea-coast These furnaces hold sixty or more shot. The shot being placed, and the furnace cold, it requires one hour and fifteen minutes to heat them to a, red heat, but after the furnace is once heated, a 24-pdr. Shot is brought to a red heat in twenty-five minutes; the 32-pdr. and 42-pdr. shot require a few minutes longer. Three men are required to attend the furnace; one takes out the hot shot, and places them on the stand to be scraped; another scrapes them and puts them in the ladle; and the third supplies cold shot and fuel.

Crates for heating shot-- In siege and other batteries, where there are no furnaces, a grate is used for heating shot. This grate consists of four bars 1.75 inch square, three fleet long, placed four includes apart on three iron stands one foot in height. It is placed in an excavation one foot in depth, of the width of the grate, perpendicular at the back and side, open in front, the legs resting on bricks' or stones rising about four or five inches from the bottom. A roof is made over it with hoops of flat iron, covered with sods and eighteen inches of earth, having in the back part a chimney six inches square.

The shot are placed on the back part of the grate, leaving one fourth of front part free; and under and on the front part the wood is put, cut in pieces about fourteen inches long and two inches thick. A thick sod is used as a register, to regulate the draught of the chimney, so that no flame can issue from the front. This grate, which will contain about fifteen 24-pdr. balls, heats them to a red heat in an hour, and will supply three guns. It requires the attendance of one man.

Heated shot do not return when cooled to their original dimensions, but retain a permanent enlargement.

Hot shot have been almost entirely given up since the adoption of the method of throwing large hollow shot from long pieces. These require but little preparation, can be used at once, and are more terrible in their effect, at the same time that they are about as accurate, since in order to prevent too great a penetration, the charge with hot shot has to be reduced.

Paixhan guns.-  In 1822, Lieut.-Col. Paixhan, of the French artillery, submitted, for the first time, his plan for throwing large heavy shells from long chambered guns ( canons-a-bombes), in the same way that solid shot is thrown. Up to that time, shells fired from long pieces had been limited to the smaller calibres; and it remained for Paixhan to prove, after the greatest opposition on the part of others, that it was as practicable and almost as easy to throw shells to a great distance with slight elevations, as to throw shot.

His piece, which was provided with a chamber, seems to have been designed more especially for the navy, though its importance as a defense against shipping in sea-coast defense was early perceived and taken advantage of; and his pieces, under the name of Paixhan guns, have been adopted in almost every service; and we are at this day witnessing the fulfillment of some of his predictions regarding the change likely to take place in the size and motive-power of naval vessels from the adoption of this new arm.

The pieces are loaded like the guns, with the additional precaution of placing the fuze towards the muzzle, and either in the axis of the piece or above it, according to the manner in which the sabot is fixed.

In Ricochet Firing the charges are very variable, according to the distance of the mark and the kind of ricochet to be used. In general, the charges are very nearly inversely proportional to the total elevation, that is, to the height on the hausse + the dispart. The smallest charge for a gun with solid shot should not be less than 1/40 omits weight.

Pointing .-- To point a piece is, to direct its axis on a mark, and give it the elevation necessary for the ball to strike the point intended. The line of sight is usually marked upon the piece, so that the firing will be accurate only when this line is in the vertical plane of fire, and the trajectory remains in this plane.

Long Guns .-- The point-blank range increases with the velocity, size, and density of the projectile.

The manner of pointing a piece to strike an object at, within, and beyond point-blank range, and the advantages of the hausse, have already been explained.

The line of sight and point-blank obtained when the hausse is used are called artificial, in opposition to those obtained without it, which are called the natural point-blank and line of sight.

The effect of the hausse, or breech-sight, is evident. The apparent increased diameter of the breech obliges us to elevate the piece, in order to have the new line of sight directed on a given object. This increases the angle of fire, and, consequently, the range.

For firing within point-blank range, the angle of sight may be diminished by using the hausse on the chase, or between the handles; but this is seldom done.

With guns and howitzers, by means of the hausse, both the elevation and direction are given at the same time; but with mortars, which are fired at a great elevation, this cannot be clone, and the piece is first given its elevation with the quadrant, either by inserting the arm in the bore, or placing it against the face of the piece, and afterwards the direction is given.

Mortars are fired either over the parapet or through embrasures. In the former case, to establish the vertical plane of fire passing through the object, a short stake is driven in the interior crest, as near as possible opposite the middle of the platform. Sighting by this stake a long one is planted about one yard in front, and in line with the target, and a cord being attached to the top of it, is stretched to the rear of the piece over the head of the first stake, and a third planted directly under the cord one yard in rear of the platform. The large stake is then removed, the cord is attached to the small one; and, when stretched over the rear one, gives the proper direction of the mark. It is not so liable to be disarranged by the enemy's shot as if attached to the large stake. When so stretched, a plumb-line attached to it will determine the vertical plane of fire passing through the object, and the centre of the platform. The axis of the piece being placed in this plane, by means of the line of metal, will evidently have the proper direction; but should the shells fall habitually out of line, the direction of the piece is corrected by means of the pointing-board, a strip of wood with a notch on one edge to fit on the rear stake, and graduated both ways from the middle, by means of which the mortar may be directed farther to the right or the left. Should the shell fall too far to the right, the cord is put to the right of the rear stake, and by varying the position, several times in succession, the proper direction will be finally reached.

If the mortar is to be fired through an embrasure, drive a stake in the middle of the embrasure, near the interior crest, and attach a cord to it, and a second in rear of the platform, as near as possible in line with the first, and the object; the last one being high, to clear the mortar with the cord, and allow the sighting. By means of the cord, and a pointing-board nailed to the rear stake, correct the shots as before. The cord is kept in its place by a little picket, which is attached to the end, and driven in rear of the rear stake.

Another method for directing a mortar, is for the gunner, with a plumb-line, to mount any object in rear of the platform, and cause a stake to be driven near the interior crest, and another in rear of the platform, in line with the first, and the object. Then, with the cord and pointing-board, rectify the firing as before .

The angle of elevation of a mark, is the angle which the line drawn frown the object to the breech of the piece makes with the horizontal.

When the object fired at and the mortar are not on the same level, the angle of greatest range, instead of being 45ºis 45º+or-½ the angle of elevation or depression of the object.  Thus to reach an object elevated 15º above a mortar, the angle of greatest range would be 45º+ 7 ½ =52 ½ ºwhile, if the object was depressed 15º ,the angle would be 45º-7½= 37½º.

The advantages of the angle of greatest range are:- 1. Economy of powder. 2. Diminution of recoil, and less strain on the piece and its platform. 3. More uniformity in the ranges. 4. Differences of a few degrees above or below cause only a slight difference in the ranges.

Should the distance to the object be very short, and the velocity of the shells not great enough on the descending branch, they must be fired under an angle of 60 º; when, of course, greater charges must be used for the same distance, the ranges obtained with 60 degrees elevation being about one-tenth less than those with 45 º. A shell fired at 60 º elevation, as it goes higher and obtains a greater velocity in falling, will strike more directly and with greater violence upon the vaults of the magazines and shelters of the enemy, and will have a greater force of penetration.

For want of howitzers, mortars may be used for ricochet firing. The least angle of elevation for mortars on their beds being 30 degrees, and the ricochet angle being but 15ºat most, the rear of the bed has to be raised up.

Stone-mortars are pointed in the same way as other mortars, but the angle of elevation, when firing stone, is 60º, in order that the stones may have a greater force of percussion. In firing grenades, the angle is about 33 º, to prevent the shells from having too great a force in falling, by which they would be buried in the ground, and their explosion become less effective.

Ricochet and vertical fires being used to batter a surface, and not an isolated point, as is the case with direct fires, can be used at night as well as in the day-time.

Night-firing.- Guns and howitzers are fixed for night-firing by measuring the distance of the handle of the elevating screw about the screw-box, or cutting a stick which will fit between the breech and trail. The direction is fixed by nailing down on the platform two strips of wood, one outside one of the wheels, the other along the trail, at such distances as to allow between them and the wheel and trail the interposition of movable strips, which are taken up when the piece is ready for firing, to prevent the stationary ones from being torn up by the recoil.

With mortars, the elevation is axed by marking the quoin, or by taking a strip upright on the bolster, so as to touch the chase. The direction of the bed is established by one movable and one fixed strip of wood along one of its cheeks.

Garrison and sea-coast carriages are the easiest to arrange for night-firing. the direction being fixed by simply chocking the wheels of the chassis.

Night-firing is evidently not so accurate as day-firing, but with due care is very efficient.

Solid Shot from Guns .- The effect of solid shot increases with the calibre and velocity. As the shot acts simply by its force of striking, the quantity of motion imparted to it should be as great as possible.

For any given piece and charge, the probability of striking an object is the greatest possible at the point-blank range, and diminishes more and more beyon d this. The largest pieces have the greatest point-blank ranges, and are, consequently for any distance, the most effective, and may, from this fact, compensate for their numerical inferiority.

Shot from field guns will easily penetrate walls from one and a half feet to two feet thick; but good masonry four feet thick is safe against them, unless a regular breach is made, which is a long operation. Experiments show that breaches can be successfully effected with 12-pounders.

Shells, in consequence of irregularities attending their construction, and being lighter, are less exact in their fire than shot, especially at great distances, their effect being estimated at two thirds that of the corresponding shot. In consequence of their noise and explosion, however, their moral effect is greater than with shot, and they are preferred, therefore, in firing against cavalry. The extreme range of field shells is sometimes as great as 2,000 yards. The number of ricochets they make is very variable, and depends on the nature of the ground. The 24- and 32-pound shells break into eighteen or nineteen deadly pieces, which are sometimes thrown 600 yards.

Shells may be made use of to open breaches in intrenchments, as on penetrating and exploding, they act like small mines. It is estimated that for every two pounds of powder which they contain two cubic yards of earth are displaced. The 32-pdr. howitzer, on account of its greater accuracy, is more suitable for this purpose than the 24. These, with their maximum. charges, send their shells from four to five feet into earth newly thrown up.

The total range of the mountain howitzer sometimes reaches 1,200 yards, after the shell has ricocheted three or four times. The 12-pound shell breaks into twelve or fifteen pieces, which are sometimes thrown 300 yards.

The shells of the 8-inch siege howitzer, in consequence of their great weight, and the

quantity of powder contained in them, 2lbs. 9 oz., are very destructive, either by destroying and setting fire to the enemy's shelters, or by destroying his parapets, traverses, or epaulements. In sea-coast defenses, these shells are formidable against ships over 3,000 yards distant. The number of effective splinters is from twenty-eight to thirty, and when filled with musket-balls (schrapnell), they become still more destructive.

Mortar Shells .-- These shells are designed to force the vaults or magazine roofs of an enemy, and to set fire to them, as also to destroy his blindages and shelters. They act by their explosion as well as by percussion. They break up the terrepleins and ditches, destroy the "pas de souris" and other communications. and end with making communication between different parts of the work very difficult.

As these shells penetrate to a considerable depth, their pieces do not produce much execution if the shells bury themselves in the ground before bursting, as some of the pieces then remain in the ground, and the rest come out at so great an angle that they are not dangerous.

The advantages in mortar-firing are on the side of the besiegers. For the works of the besieged present a great mark, which it is not difficult to hit; whilst the batteries and works of the besiegers form but narrow bands around the work, which are difficult to strike, especially as the deviations in the direction of the range are much greater in mortars than the lateral deviations.

The greatest difficulty in firing these shells is to regulate the charges properly. Very great differences are found to exist between ranges obtained under the same circumstances, and these increase with the range, whilst the lateral deviations are much less. Firing at a bastion or demi-lune at 600 yards, scarcely one fifth of the shells will fall into the work; at 400 yards, about one third.

The best method of firing these shells is to direct the mortars and place the batteries in such a way, that the shells will pass over the works fired at in the direction of their greatest extent.

The 8-in. shell being the same as that used for the siege howitzer, gives from the mortar the same number of fragments (30), some of which are thrown to 600 yards. The 10 and 13-in., in consequence of their greater thickness, do not form so many fragments. When firing against men, it is best to use small angles of elevation, and 8-in. shells are preferable to the larger calibres.

These shells will penetrate compact earth from 15 to 38 inches at 600 yards. The earth displaced is in the same proportion as for howitzer shells, two cubic yards for every two pounds of powder contained in the shell. The diameter of the top of the hole made is usually two or three times the depth. Sometimes the largest shells are broken by falling on a stone pavement. Good masonry arches, three feet thick, are sufficient to resist the largest shells falling with their maximum velocity.

Mortar-firing at sea is very uncertain, but when shells do strike a vessel, the effect is terrible.  A 10 or 13-in. shell falling upon a three-decker, will sometimes pass entirely through and sink the vessel.

Light and fire-balls, according to their size, are fired from mortars of corresponding calibres. With a charge of 1/25 of its weight, they are thrown from 600 to 700 yards.

The smallest angle under which siege mortars can be fired without raising the rear part of the bed, is 30º.

The coehorn mortar is either fired from behind intrenchments, like other mortars, or it may accompany troops in effecting lodgments in towns and fortified places.

As the shell is without ears, it should be strapped with tin, having loops attached, through which a cord is passed for the purpose of lowering it into the bore.

In firing stone-mortars, the stones or shells leave the piece, as in firing grape-shot, in the form of a cone which meets the ground in a more or less irregular section, from 30 to 50 yards wide by from 60 to 90 yards long. Some of the grenades fall near the battery, but the greater part are found within a circle of from 20 to 30 yards in diameter. Each grenade bursts into 12 or 15 fragments, which are effective within a radius of 10 to 20 yards, and some even as far as 300 yards.

Time Of Flight .-- The time of flight for siege-mortars, at an elevation of 45 º, with ordinary charges, is nearly equal to the square root of the range in feet divided by four. The experimental length of the fuze may be given. according to this rule.

Schrapnell shot have only enough powder placed in them to rupture the case and set the balls free. Consequently, their effect is greater the greater the velocity they have at the moment of bursting. 12-pound schrapnell are effective up to 800 yards.

Grape and Canister shot leave the piece diverging from each other, in the form of a cone, the greater part of the balls being in the centre, and the extreme ones separating about one-tenth of the range. When fired at too short a distance, the balls occupy too small a space to produce the proper effect; and at too great a distance they diverge too much, and strike on too extended a surface. Good results can be obtained at from 300 to 600 yards, but the maximum effect is produced at from 300 to 450 yards. When firing at very short distances over hard, dry ground, a suitable dispersion of the balls may be produced by firing very low, and allowing the balls to ricochet.

The range and effect of grape-shot become greater, at ordinary distances, as the size of the balls is increased. For this reason, the grape from 12-pdr. guns and 32-pdr. howitzers, is more effective than that from 6-pdr. guns and 12 or 24-pdr. howitzers, and the 6-pdr. Grape is no longer used in the United States.*

 * Grape-shot is now no longer used with any of our field-pieces.

If the balls ricochet over-hard, dry ground, grape-shot may be effective up to 800 yards, and the pointing is of but little importance; but with broken or soft ground, ricocheting cannot be depended on, and the angle of elevation should be regulated with care.

To ascertain the distance by the report of firearms, multiply the number of seconds which elapse between seeing the flash and hearing the report by 1,100; the product will be nearly the distance in feet.

Rapidity of Firing .-- Siege-mortars can be fired conveniently at the rate of twelve rounds an hour continuously; but they may, in case of need, be fired with greater rapidity. In general, the rate of firing depends on the calibre of the piece. A 24-pdr. takes about double the time to load and fire it that a 12-pdr. does.

For field-guns, 30 or 40 seconds are required for the 6-pdr., and one minute for a 12-pdr. The mean rate is about one shot per minute, but when close pressed, and firing at objects not difficult to hit, two or three shots per minute can be fired.

The firing of howitzers is always slower than with guns, a 24 or 32-pd. field-howitzer requiring 1 ½ minute to load and fire it. The mean rate of siege guns is about 8 shots an hour, though this can be increased on an emergency to 12 shots; and in breaching, as many as 20 shots per hour have been fired. But this rapid firing is very injurious to pieces, especially bronze guns, which heat rapidly, soften, and lose their resistance.

Rockets can be fired more rapidly than any other kind of projectile; and if large quantities of them are on hand, they constitute the best means of setting fire to towns. They are fired from troughs or sheet-iron tubes, the former being the most rapid but the least accurate means.

The elevations are given with a quadrant, and the direction with a plumb-line.

Recoil.-- The recoil of the carriages varies between very extended limits, according to the nature of the ground. Generally, howitzers recoil more than the corresponding guns, and the 6-pdr. recoils less than the 12-pdr. The 24 and 32-pdr. howitzers fired with large charges sometimes recoil 10 yards; whilst under some circumstances the 6-pdr. gun will recoil but 1 ½ or 2 yards. The mountain howitzer will recoil 11 or 12 yards, but may be limited to 4 by using a rope on the wheels.

When the piece is on a platform, as with siege-pieces, the recoil is seldom more than 4 yards, unless the platform is wet, when it increases from the reduction of friction on the trail. 

The recoil on garrison-carriages is very slight, as is also the case with mortar beds.

Penetration-- For the penetration of shot and shell, see the Ordnance Manual, pp. 368 to 373.

It is remarked in firing leaden bullets into earth or water, that they are flattened the more as the velocity is increased. This affects their penetration, so that fired at a distance of 50 yards the penetration is greater than at a distance of 25 yards. The same effect is noticed, though not to the same extent, in firing into other materials. Beyond a certain limit, the flattening of the ball does not sensibly affect the penetration.

Tables of Fire-- Tables of fire should be considered simply as a means of limiting the number of trials to be made before finding out the range of a gun, and not as giving accurate results which will be the same under all circumstances. The first shots always produce the greatest effect on an enemy; and it own happens in battle that the smoke and dust prevent subsequent rectifications in the firing, unless a certain amount of information is possessed in regard to the effects of the piece. In giving this information, the tables of fire are of use.

If, in experimental firing, great differences are observed between two successive shots, fired with the same charge, same powder, from the same piece, under the same angle and at well known distances,-- we should not be surprised to find differences between the tables of fire and the results obtained in the presence of an enemy. These tables, then, give simply the first term of a series of trials, by the aid of which a skilful gunner arrives at accuracy in pointing.

This first term is, however, often of the greatest importance, since, by knowing it, a great deal of time is gained.

For these tables, see Appendix, pp. 455 to 463; and for the initial velocities and penetration of small-arms, p. 464.

Breaching .- A breach is an opening made in the wall of a fortified place, to facilitate the entrance of a storming party.

In permanent works, the wall being formed of masonry, little if any part of which is  exposed to the fire of artillery at any great distance, it becomes necessary to establish breaching batteries, for the purpose of knocking it down. These batteries are established in the covered way, or on the crest of the glacis, where the guns can be brought to bear upon the wall.

Before the use of iron as a material for balls, stone was used, which, not being so resisting, broke against the solid wall without producing much damage; and the wall had to be knocked down by commencing at the top, where the least resistance was offered, and continuing to fire down the face until sufficient debris was formed to make a ramp from the bottom of the ditch. This method was very laborious, and generally formed a very steep and often impracticable slope.

The ball, when it strikes, is acted upon by the elasticity developed by the shock; and is sometimes thrown back 150 yards, so as to be dangerous to those in the battery. Pieces of masonry are also sometimes thrown from the wall 50 or 60 yards. The opening made and penetration depend upon the kind of material of which the wall is made, and upon the caliber and velocity of the projectiles used.

If the axis of the piece is perpendicular, or nearly so, to the face of the wall, no difficulty is experienced in making the ball penetrate; but where the ball strikes the wall at a much smaller angle, it is not so easily done. Against solid masonry, a ball striking under a less angle than 33º, will glance off without producing much effect; and when no greater angle can be obtained, the same spot must be fired at until a hole is started. Then the cut is made with more ease, though with nothing like the rapidity with which it is effected when firing directly against the face of the wall.

The breaching batteries having been established, several pieces in each, the number depending upon their calibre and the size of the intended breech, the first thing to do is to make a horizontal cut in the wall. The determination of the proper position for this cut is a matter of importance, as on it depends in a great measure the practicability of the breach.

The ramp formed of the falling masonry and earth diminishes as the height of the cut is increased; so that if the cut is made too high, a part of the scarp wall will remain standing above it, and if it cannot be ascended will require a long time to knock down.

If, on the contrary, the cut is made too low, the amount of material for forming the ramp is increased, and may mask the openings first made before the cut is completed.

Hence, the most suitable height is that which will furnish about sufficient material to reach the cut. This height is determined to be nearly equal to the thickness of the wall at the cut.  This thickness, when not previously known, can be deduced from the dimensions necessary to be given to the wall to resist the pressure of the earth of the rampart and parapet.

A profile may be constructed, by ascertaining as near as possible the width of the ditch, that of the covered way, the height of the scarp, the thickness of the parapet, the height of the counter-scarp, and crest of the covered way. From this profile, the position of the cut is determined, so that the resultant ramp shall have a slope of 45º. The height of this cut should never be less than one-fourth the height of the scarp. If the ditch is a wet one, the cut should be made at the water's edge.

The number of pieces in the battery, and the length of the breach to be made, will determine the field of fire of each piece, and the length of cut to be made by it.

The angle of depression for each piece should be determined as near as possible beforehand, and when once satisfactorily obtained, should be marked on the elevating screw.

Frequent inspections are made to see that the cut progresses uniformly; and if some portions are formed more rapidly than others, adjacent pieces may be turned against the slowest parts.

The vertical cuts, Fig. 170, are made between the horizontal cut and the top of the wall. There must be one at each end of the breach, and intermediate ones at a distance apart of not more than 10 yards, and closer if possible, so that no part of the wall may be sustained by more than one counterfort. The number of these cuts should not exceed the number of pieces in the battery, so that each one may be fired at by at least one piece. The firing is commenced just above the horizontal cut, and continued upwards, slowly at first, so as not to encumber the cuts with the falling material. The shots are spaced at first about half a yard apart, and after that the salient points fired at. The extreme cuts should progress at least as rapidly as the intermediate ones, so that the whole weight of the wall will come upon the ends, and assist in bringing it down. If necessary, the adjoining guns are directed upon the extreme cuts.

If time and other circumstances permit, these shells are fired from 8-inch howitzers, which replace the breaching guns; but if this cannot be done, shells are fired from the guns themselves.

The time necessary to make a practicable breachs depends upon the length of it, the material of which the scarp is made, the number and calibre of the guns, &c. For a breach 20 or 30 yards long, at 40 yards from the battery, 1,500 shot of large calibre are required; but when the firing distance is greater, the estimate must be larger, on account of the less penetration and accuracy of each shot. Thus at 500 to 600 yards, 9,000 or 10,000 projectiles, or even more, may be required.

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