Chapter XLVII: Part 47

=Primer.= A wafer, cap, tube, or other device for communicating fire to the charge of powder in a cannon. The cap or tube usually contains a friction- or percussion-powder. The _friction-primer_ is generally used in the land service. (See FRICTION-PRIMER.) For service on shipboard, a quill filled with rifle-powder, having on the top a capsule of fulminate of mercury, is generally employed. The capsule is exploded by a blow from the lock-hammer. The _tape-primer_, used sometimes in blasting, is formed of long, flexible strips of paper or fabric containing fulminate or other quick-burning substance. The _electric primer_ is used to fire simultaneous discharges, both in ordnance and blasting. In firing wet gun-cotton, the small charge of dry gun-cotton used in conjunction with the _detonating exploder_ is called a _primer_. In _small-arms_ the term is specially applied, at the present time, to the percussion-caps used in reloading metallic cartridge-cases. The cap is set in a recess in the head of the shell. When the firing-pin strikes the outside end of the cap, the fulminate is exploded by being driven against a perforated cone called the _anvil_. This _anvil_ is usually a part of the shell. In the _Winchester primer_, recently invented, the anvil is a part of the primer itself, being inserted upon the fulminate. A shoulder in the recess holds the anvil when the cap is struck.

=Priming.= The powder, percussion-cap, or other device used to communicate fire to the charge in a fire-arm.

=Priming-tubes.= See LABORATORY STORES.

=Priming-wire.= A pointed wire, used to penetrate the vent of a piece, for examining the powder of the charge, or for piercing the cartridge.

=Primipilarii=, =Primopilarii=, or =Primipilares=. Among the Romans, were such as had formerly borne the office of primipulus of a legion. The banner was intrusted to his care. Among other privileges which the primipilarii enjoyed, they became heirs to what little property was left by the soldiers who died in the campaign.

=Primipilus.= The centurion belonging to the first cohort of a legion. He had charge of the Roman eagle.

=Princeton.= A town of Mercer Co., N. J., about 40 miles northeast of Philadelphia. This place was the scene of an important engagement during the Revolutionary struggle, although the numbers engaged were comparatively small. On hearing of the English reverse at Trenton (which see), Gen. Howe immediately ordered Cornwallis, who was in New York, to proceed with his forces to Princeton. Leaving a part of his troops at this place, he proceeded towards Trenton with the intention of giving battle to the Americans, and arrived with his vanguard on January 1, 1777. Washington, learning that only three regiments were left at Princeton, by a circuitous night march arrived there by daybreak of January 3, surprised and completely routed the enemy with a loss of 200 killed and wounded, and as many prisoners. The American loss did not exceed 30. This event greatly aroused the drooping spirits of the colonists, who had been previously disheartened by a series of reverses.

=Principes.= In the Roman armies, were the infantry, who formed the second line in the order of battle. They were armed like the _hastati_, with this difference, that the former had half-pikes instead of whole ones.

=Principles, Military.= The basis or ground-work upon which every military movement is made, and by which every operation is conducted.

=Prismatic Compass.= A surveying instrument, much used on account of its convenient size and form in military sketching, and for filling up the details of a map where great accuracy is not required.

=Prismatic Powder.= See GUNPOWDER.

=Prisoners.= Are persons under arrest or in custody, whether in prison or not. Whenever any officer is charged with a crime, he is to be arrested and deprived of his sword by the commanding officer; and soldiers charged with crimes are to be confined until tried by a court-martial, or released by proper authority. (See APPENDIX, ARTICLES OF WAR, 65 and 66.) When brought into court, a prisoner should be without irons, or any manner of shackles or bands, unless there is danger of an escape, and then he may be secured with irons.--_Blackstone._

=Prisoners of War.= Are soldiers captured during an engagement, siege, or continuance of hostilities, who are deprived of their liberty until regularly exchanged.

=Prisons, Military.= Are buildings constructed for the retention of prisoners of war, or for the safe-keeping and punishment of offenders against military law. Sometimes during war forts and other strong buildings are utilized for these purposes. The following were noted prisons during the civil war, 1861-65, for the retention of Federal prisoners of war:

_Andersonville_ (which see).

_Belle Isle._--An island in the James River near the city of Richmond, Va. The unfortunate prisoners taken were placed on this island without shelter of any kind to protect them from the scorching rays of the sun during the day or the chilly cold mists of the night, until death or exchange released them from their sufferings.

_Castle Thunder._--A fort in Charleston harbor, S. C., which was used for the same purpose.

_Libby._--An old tobacco warehouse in Richmond, Va., which was temporarily converted into a military prison; and for cruelty and torture to the Union prisoners this place was second only to Andersonville.

_Salisbury._--A town in North Carolina, which had another depot for prisoners.

There were also prisons established for the retention of Confederate prisoners at Camp Douglas, Chicago, Camp Chase, Ohio, Elmira, N. Y., Point Lookout, Md., and Rock Island, Ill.

At _Fort Leavenworth_, Kansas, a permanent military prison was established in accordance with an act of Congress passed March 3, 1873, in which soldiers of the U. S. army are confined for serious offenses against military law.

At _Dartmoor_, a desolate region in England, a prison was constructed in 1809 for the confinement of French prisoners of war which deserves a passing notice, inasmuch as Americans were confined there during the war of 1812. It comprised 30 acres, inclosed with double walls, with seven distinct prison-houses with inclosures. In 1812 there were 6000 American prisoners of war within its walls who were treated with much cruelty, and, in consequence of the appearance of mutinous intentions of some of the prisoners on account of the tardiness of the English officials in releasing them after the treaty of peace was ratified, they were fired upon by the English soldiers, which resulted in the killing of 5 and wounding of 33 prisoners. This act was regarded in America as a wanton massacre.

=Privas.= A town of France, capital of the department of Ardèche, 26 miles southwest from Valence. In the civil wars of the 16th and 17th centuries in France, Privas, which was then a strongly-fortified town, played a conspicuous part, being always favorable to the Protestant party. In 1629 it was bravely defended by a small garrison under St. André de Montbrun against Louis XIII., but after a siege of two months had to be abandoned. Montbrun being soon afterwards taken was hanged, and the fortifications of Privas were leveled to the ground.

=Private.= The title applied in the British army to a common soldier of the cavalry and infantry; the corresponding rank in the artillery being gunner or driver, and in the engineers, the sapper. A private in the cavalry is sometimes called a trooper. In the U. S. army all the soldiers who are below the grade of non-commissioned officers are called privates.

=Privy-coat.= A light coat or defense of mail, concealed under the ordinary dress.

=Prize.= That which is taken from another; a thing seized by force, stratagem, or superior power. Hence, specifically, anything captured by a belligerent using the right of war.

=Prize.= The application of a lever to move any weighty body, as a cask, cannon, or the like.

=Prize Agent.= In the British service, a person appointed for the distribution of such shares of money as may become due to officers and soldiers after battle, siege, or capture.

=Prize-bolt.= A manœuvring-bolt of a mortar-bed.

=Prize-money.= The proportion which is paid to the troops who are present at the capture or surrender of a place, etc., which yields booty.

=Prizing.= The same as _prize_, which see.

=Proclamation.= The act of publishing abroad; conspicuous announcements; official or general notice; publication; that which is put forth by way of public notice; an official public announcement or declaration; a published ordinance; as, the proclamation of a king. A proclamation may be issued to declare the intention of the head of a government to exercise some prerogative or enforce some law which has for a long time been dormant or suspended. In time of war, the head of the government by a proclamation may lay an embargo on shipping, and order the ports to be shut. But the most usual class of proclamations are admonitory notices for the prevention of offenses, consisting of formal declarations of existing laws and penalties, and of the intention to enforce them. Proclamations are only binding when they do not contradict existing laws, or tend to establish new ones, but only enforce the execution of those which are already in being, in such manner as the head of the government judges necessary.

=Proconsul.= In Roman antiquity, an officer who discharged the duties of a consul without being himself consul; a governor of a province, or a military commander under a governor. He was usually one who had previously been consul, and his power was nearly equal to that of a regular consul.

=Prodd.= A cross-bow, used for throwing bullets in ancient times.

=Profile.= A section of a parapet or other work in fortification.

=Projectile.= A body projected or impelled forward by force, especially through the air. In a limited military sense the term is applied to a body intended to be projected from a cannon by the force of gunpowder, or other explosive agent, to reach, strike, pass through, or destroy a distant object. The materials of which projectiles are usually composed are lead, wrought or cast iron, each possessing advantages according to the circumstances under which they are fired. But the material which combines in a greater degree than any other the essential qualities of hardness, strength, density, and cheapness, is cast iron, which is exclusively used in the U. S. service for large projectiles. Compound projectiles are sometimes made, so as to combine the good and correct the bad qualities of different metals. To obviate the serious results that may arise from the wedging of the flanges of a cast-iron projectile in the grooves of a rifle-cannon, it is frequently covered with a coating of lead or other soft metal. Cast and wrought iron have also been combined with success, and also cast iron and soft metal in such a manner as to attain the strength of one metal and the softness and expansibility of the other. Other metals, such as brass, are also used in projectiles of special construction. Projectiles are generally classified, according to their form, into spherical, or smooth-bore, and oblong, or rifle projectiles.

_Spherical Projectiles_ are fired mainly from smooth-bore guns. They are solid shot, shells, spherical case or shrapnel, grape, canister, carcasses, grenades, light- and fire-balls. The advantages which they possess over the oblong are their uniformity of resistance to the air, presenting the least extent of surface for a given weight, the coincidence of their centres of form and inertia; they are less liable to wedge in the bore, as they touch the surface at only one point; and they are best adapted for rolling and ricochet fire on account of the regularity of their rebounds. Solid shot are usually made of cast iron, and are designated by the diameter of the bore of the piece in which they are to be used, or by their weight. Shells are cast with a core of sand (greater or less according to the thickness required), which is afterwards removed. The mortar-shell has the thinnest walls, and contains the greatest bursting charge for the same caliber; the gun-shell is thicker, and the battering-shell is nearly as strong as the solid shot. Shells are usually designated by the weight of the solid shot of the same diameter.

_Oblong Projectiles_ are fired principally from rifled pieces, and have been adopted on account of the increase of range and accuracy which can be obtained with them. For this purpose it is necessary that the projectile should move through the air in the direction of its length. Though experience would seem to show that the only sure method of effecting this is to give it a rapid rotary motion round its axis by the grooves of the rifle, numerous trials have been and are now being made to produce the same effect with smooth-bored guns. One of the simplest plans for this purpose is to place the centre of gravity or inertia in advance of the centre of figure. Another is to make the projectile very long, with its rear portion of wood, and its point of lead or iron, somewhat after the manner of an arrow; but these plans do not seem to be of much practical utility. The system by which the desired result is obtained with the greatest certainty is the rifle system.

_Rifle System._--Spiral grooves are cut into the bore of the piece, or it is ribbed with spiral bands, and the projectile is so formed or prepared as to follow them as it passes along the bore of the piece. The principal question which now occupies the attention of those engaged in improving this species of cannon is to obtain the safest and surest means of effecting this object. Various plans have been tried to obtain the proposed object; nearly all may be ranged under the following heads:

1. _The Flanged System._--This comprises all projectiles which have certain flanges or projections to fit into the grooves of the gun in loading. These are usually deep and few in number, rounded at their bottom edges so as to cause the flanges or studs to pass up the inclined side when rotation is imparted. This is the system at present adopted in England. Though this plan affords a certain means of communicating the rifle motion, it has not always been found a safe one, probably from the wedging of the flanges in the grooves. Besides, the dirt from the burning of the powder collects in the grooves; and as it is difficult to clean them by the usual means, the projectile is liable to meet with obstruction in loading. To obviate these difficulties, the flanges are sometimes made of softer metal than the body of the projectile. Guns for flanged or studded projectiles usually have from 3 to 9 grooves, 0.15 to 0.25 inch deep.

2. _The Compressive System._--By this system the projectile is forced by the action of the powder through the bore of a piece whose diameter without the grooves is less than the diameter of the projectile. Such are the projectiles for the breech-loading Krupp and Broadwell guns. These usually consist of cast iron or steel, and are covered with a coating of lead or other soft metal having horizontal ribs or corrugations, which is secured by a chemical solder, or cast into undercuts in the body of the shot. As the projectile is forced through the bore, an impression of the rifling is cut out of the ribs, the lead thus displaced finding room in the grooves between. This system has been found to work satisfactorily in breech-loading guns. The rifling should be shallow and consist of numerous grooves, slightly narrowing towards the muzzle. Large guns usually have from 20 to 76, from .05 to .08 inch deep. Experiments are now being made, with prospects of success, to substitute bands of soft copper encircling the projectile for the lead coating.

3. _The Expansive System._--This system has been so exclusively used in the United States that it has frequently been called the American system. It embraces all projectiles which are loaded without regard to the rifling, but which are fitted with an expanding portion of some softer metal, as pewter, copper, wrought iron, or _papier-maché_, which is forced into the grooves by the discharge. This system requires for its rifling fewer grooves than the compressive, but a somewhat greater number than the flanged system. Among the projectiles of this class used during the civil war were the Blakely, Dyer, Hotchkiss, James, Parrott, Reed, Schenkle, and Stafford. The principal objections to an expanding or compound projectile are its want of strength to resist a charge of powder proportionately as large as that employed for a simple projectile, and the danger of its breaking and wedging in the bore of the piece. Of late years, however, marked improvements have been made, and projectiles of this class can now be safely fired with double their former charges. The large projectiles of this description now used in the United States consist of the usual cast-iron body having a sabot, or ring of brass or copper either cast or screwed to its base. This ring is divided into an upper and lower flange or lip by an annular groove. When the gun is fired, the gases enter this groove, forcing the lower flange down upon the projectile and the upper or outer into the rifling of the gun, where it is kept during its passage through the bore.

_Armstrong Projectile._--But one kind of projectile is used in the Armstrong breech-loading guns for the field service, and this is so constructed as to act as a shot, shell, or case-shot at pleasure. It consists of a very thin cast-iron shell, inclosing 42 segment-shaped pieces of cast iron built up so as to form a cylindrical cavity in the centre, which contains the bursting charge and the concussion-fuze. The exterior of the shell is thinly coated with lead, which is applied by placing the shell in a mold and pouring it in a melted state. The lead is also allowed to percolate among the segments, so as to fill up the interstices, the central cavity being kept open by the insertion of a steel core. In this state the projectile is so compact that it may be fired without injury, while its resistance to a bursting charge is so small that less than one ounce of powder is required to burst it. When the projectile is to be tired as a shot, it requires no preparation; but the expediency of using it otherwise than as a shell is doubted. To make it available as a shell, the bursting tube, the concussion- and time-fuzes, are all to be inserted; the bursting tube entering first and the time-fuze being screwed in at the apex. If the time-fuze be correctly adjusted, the shell will burst when it reaches within a few yards of the object; or failing in this, it will burst by the concussion-fuze when it strikes the object, or grazes the ground near it. If it be required to act as a canister-shot upon an enemy close to the gun, the regulation of the time-fuze must be turned to the zero of the scale, and then the shell will burst on leaving the gun. The Armstrong projectiles for the muzzle-loading guns have rows of brass or copper studs projecting from their sides to tit into the grooves of the gun, which are constructed on the _shunt_ principle. The projectile is made of wrought iron, or low steel, with very thick sides. There is no fuze, the explosion resulting from the heat generated by the impact, and the crushing in of the thin cap which closes the mouth of the powder-chamber. The sides and bottom of the shell being thick enough to resist crushing by the impact, and also to resist the explosive force of the bursting charge, its effect will, after penetration, be expended on the backing of the armor, or the decks which the armor is intended to screen. Such projectiles are called “blind shells.”

_Blakely Projectile._--Capt. Blakely’s projectile has an expanding cap attached to its base by means of a single tap-bolt in the centre. It is prevented from turning by radial grooves cast on the surface of the bottom of the projectile, into which the cup is pressed by the charge. The angle between the curved sides of the cup and the bottom of the projectile is filled with a lubricating material. On the forward part of the body are soft metal studs, more numerous than the grooves of the bore of the piece, that some of them may always form a bearing surface for the projectile against the lands. The driving sides of the grooves are deeper than the others.

_Dyer Projectile._--The Dyer projectile is composed of a cast-iron body, and a soft metal expanding cup, attached to its base. The adhesion of the cup is effected by tinning the bottom of the projectile, and then casting the cup on to it. The cup is composed of an alloy of lead, tin, and copper, in certain proportions. This projectile, as improved by Mr. Taylor at the Washington Arsenal, gives good results for even as large a caliber as 12 inches.

_French Projectile._--The projectile used in the French field service is made of cast iron, and has 12 zinc studs on its sides, arranged in pairs, so as to fit the 6 grooves of the gun. For the larger cannon projectiles, but 3 studs are used, and these are cast on the projectile, nearly opposite to its centre of gravity; the bearing sides of the studs are faced with white metal to diminish friction against the grooves of the bore. The shape of the grooves is such as to centre the projectile. The latter projectile is used with increasing, the former with grooves of uniform twist. Russian, Austrian, and Spanish artillery projectiles belong to the studded, or button class, but differ from each other in the details of their construction.

_Hotchkiss Projectile._--The Hotchkiss projectile is composed of three parts: the body, the expanding ring of lead, and the cast-iron cup. The action of the charge is to crowd the cup against the soft metal ring, thereby expanding it into the rifling of the gun. The time-fuze projectile has deep longitudinal grooves cut on its sides to allow the flame to pass over and ignite the fuze. The last rifle projectile submitted by Mr. Hotchkiss has an expanding cup of brass attached to its base in a peculiar manner. The cup is divided into four parts by thin projections on the base of the projectile. This arrangement is intended to facilitate the expansion of the cup and to allow the flame to pass over to ignite the fuze.

_James Projectile._--The expanding part of the James projectile consists of a hollow formed in the base of the projectile, and eight radial openings, which extend from this hollow to the surface for the passage of the flame of the charge, which presses against and expands into the grooves of the bore, an envelope or patch, composed of paper, canvas, and lead. In a later pattern of this projectile, the internal cavity and radial openings are omitted, and the outside is furrowed with longitudinal grooves which increase in depth towards the base of the projectile, forming inclined planes, up which the outer covering of lead and canvas is moved by the force of the charge and expanded into the rifling of the piece.

The first projectile used in Parrott guns was invented by Dr. Reed of Alabama, in 1856 or 1857, and was made at Parrott’s foundry. It consisted of a soft wrought-iron cup, slightly swedged to fit the grooves, upon which was cast the body of the shot.

_Palliser Projectile._--This is the most formidable armor-piercing projectile in use. It owes its efficiency to the material used,--chilled cast iron. In the later forms the head only is chilled, the body being cast in sand. Both shot and shell are cast with a core. The shell is “blind.” The curve of the ogival head is struck with a radius of one and one-half times the diameter of the projectile.

_Parrott Projectile._--Capt. Parrott’s projectile, as now made, is composed of a cast-iron body with a brass ring cast into a rabbet formed around its base. The flame presses against the bottom of the ring and underneath it so as to expand it into the grooves of the gun. To prevent the ring from turning in the rabbet, the latter is recessed at several points of its circumference. _Parrott’s incendiary shell_ has two compartments formed by a partition at right angles to its length. The lower and larger space is filled with a burning composition, the upper one is filled with a bursting charge of powder, which is fired by a time- or concussion-fuze. The burning composition is introduced through a hole in the bottom of the shell, which is stopped up with a screw-plug.

_Sawyer Projectile._--The Sawyer projectile has upon its sides six rectangular flanges or ribs to fit into corresponding grooves of the bore. To soften the contact with the surface of the bore, the entire surface of the projectile is covered with a coating of lead and brass-foil. The soft metal at the corner of the base is made thicker than at the sides to admit of being expanded into the grooves, and thereby closing the windage. In the latest pattern of Sawyer projectiles, the flanges are omitted, and the projectiles are made to take the grooves by the expansion of the soft metal at the base, which is peculiarly shaped for this purpose.

_Schenkle Projectile._--Schenkle’s projectile is composed of a cast-iron body, the posterior portion of which is a cone. The expanding portion is a _papier-maché_ sabot or ring, which is expanded into the rifling of the bore by being forced on to the cone by the action of the charge. On issuing from the bore the wad is blown to pieces, leaving the projectile unencumbered in its flight. A great difficulty has been found in practice in always getting a proper quality of material for the sabot, and in consequence, these projectiles have not been found to be reliable.

_Scott Projectile._--The shell devised by Commander Scott of the British navy, for firing molten iron, has three ribs cast upon it, which fit grooves so constructed as to centre it in the bore of the gun when fired. The interior of this shell is lined with loam to prevent the heat of the charge from penetrating through to the bursting charge. It is supposed to be broken and its contents diffused on striking the object.

_Whitworth Projectile._--The cross-section of the bore of the Whitworth gun is a hexagon with the corners slightly rounded. The projectile is first formed so that its cross-section is a circle, and its sides taper towards both ends. The middle portion is then carefully planed off to fit the bore of the gun. The Whitworth blind shell for firing against armor-plates, is made of tempered steel, and each end is closed with a screw. To prevent the heat of impact from acting too soon on the bursting charge, it is surrounded by one or more thicknesses of flannel. A 7-inch shell of this kind has been found to have sufficient strength and stiffness to penetrate 5 inches of wrought iron before bursting.

_Confederate Projectiles._--The rifle projectiles used by the Confederates in the late war belonged, with a few exceptions, to the expanding class. Besides the above there are three kinds of projectiles much used in the U. S. service, viz.:

_Absterdam Projectile._--The best form is cast in a single piece, and has an expanding ring of brass which projects three-eighths of an inch beyond the base of the projectile.

_Eureka Projectile._--Consists of a cast-iron body in one piece, with a brass sabot; the sabot is an annular disk intended to move on the frustum of a cone with an expanding cup in rear to take the grooves.

_Ordnance Projectile._--Consists of a cast-iron body, with a sabot composed of an alloy of lead and tin, which is cast on the base of the projectile, and is held in position by undercuts and dovetails, the action of the charge being to force the sabot on the cast-iron body and to make it take the grooves.

Projectiles of special construction were formerly much used for particular purposes, as:

_Bar-shot_, which consisted of two hemispheres or spheres connected by a bar of iron either rigidly or in such a manner as to traverse its length; these were useful in cutting the masts and rigging of ships.

_Chain-shot._--This differed from bar-shot only in the mode of connection, which was a chain instead of a bar.

_Chain-ball._--To arrest the motion of rotation of an oblong projectile thrown under high angles, and with a moderate velocity, it has been proposed to attach a light body to its posterior portion by means of a cord, or chain, which will offer a resistance to the flight of the projectile, and cause it to move with its point foremost.

_Nail-ball._--A round projectile, having a projecting pin to prevent it from turning in the bore of the piece.

_Grooved Ball._--An oblong projectile, having spiral grooves cut along its base, by means of which the action of the charge produces rotation about the longer axis of the projectile. Sometimes these grooves are cut in the forward part of the projectile for the action of the air. Neither of these plans has succeeded in practice.

_Bullets._--A bullet is a leaden projectile discharged from a musket, fowling-piece, pistol, or similar weapon.

_Spherical Bullets._--When smooth-bore muskets alone were used the bullets were chiefly spherical in form and made by casting; at present, however, spherical bullets are manufactured by a compressing machine invented by Mr. George Napier. They are denominated by the number contained in a pound. In consequence of the great improvements that have been made of late in small-arms, the spherical bullet is now very little employed for military purposes, its use being chiefly confined to case-shot.

_Oblong Bullets._--Are denominated by their diameter and weight. About 1600, when rifles began to be used as a military weapon, spherical bullets were fired; in the early part of the 18th century, however, it was found that good results could be obtained by the use of oblong projectiles of elliptical form. The great difficulty, however, of loading the rifle, which was ordinarily accomplished by the blows of a mallet on a stout iron ramrod, prevented it from being generally used in regular warfare. The foregoing plan was afterwards improved by making the projectile a little smaller than the bore, and wrapping it with a patch of cloth greased to diminish the friction in loading. The improvements which have been made in the last thirty years have entirely overcome this difficulty, and rifles are now almost universally employed, although until 1855 the mass of the American infantry was armed with smooth-bored muskets. The first person to overcome the difficulty of loading rifles was M. Delavigne, an officer of the French infantry. His plan, proposed in 1827, was to make the projectile small enough to enter the bore easily and to attach it to a sabot, which, when in position, rested upon the shoulder of a cylindrical chamber formed at the bottom of the bore to contain the powder. In this position the projectile was struck two or three times with the ramrod, which expanded the lead into the grooves of the barrel. The method of Delavigne was afterwards improved by Thouvenin and Minié, both officers of the French service. The projectiles suggested by them were elongated in form and the metal of the projectile was forced into the grooves of the rifling by means of a plug or cup driven into the base of the projectile, which was cast hollow for that purpose. The cup used in the Minié bullet wits made of sheet-iron. Mr. Greener of England appears to have been the first person to utilize this expanding or dilating action. Various other bullets have been invented, of greater or less usefulness, as the Whitworth, Pritchett or Enfield, and those used in the French, Austrian, and Swiss services. In the British service, the Enfield bullet is employed; this has a perfectly smooth exterior, and a conical boxwood plug inserted into a cavity at the base; they are made by machinery which draws in a coil of leaden rod, unwinds it, cuts it to the required length, stamps out the bullets with steel dies, drops them into boxes, and conveys them away.

_United States Bullets._--The bullets used in the U. S. service are of two kinds, one for the rifle and carbine ball-cartridge weighing 405 grains, the other for the revolver cartridge weighing 230 grains. The metal used is an alloy of 16 parts of lead and 1 part of tin. The bullet in shape is a cylinder surmounted by a conical frustum terminating in a spherical segment. It has three rectangular cannelures which contain the lubricant. This latter is protected by the case which covers more than half the length of the bullet. A dished cavity is made in the base of the bullet to bring it to the proper weight.

=Projectiles, Theory of.= Is the investigation of the path, or _trajectory_ as it is called, of a body which is projected into space. A body thus projected is acted upon by two forces, the _force of projection_, which, if acting alone, would carry the body onwards forever in the same direction and at the same rate; and the _force of gravity_, which tends to draw the body downwards towards the earth. The force of projection acts only at the commencement of the body’s motion; the force of gravity, on the contrary, continues to act effectively during the whole time of the body’s motion, drawing it farther and farther from its original direction, and causing it to describe a curved path, which, if the body moved in a vacuum, would be accurately a parabola.

_Trajectory in Vacuo._--This general theory is not the object of the present discussion, but simply the theory of projectiles as far as it relates to fire-arms. The path that the centre of gravity of a projectile would describe in _vacuo_ would be a parabola, and the greatest range given by an angle of fire of 45°. Under the same angles of fire the range would be proportional to the squares of the velocities, the velocity least at the summit of the trajectory, and the velocities at the two points in which the trajectory cuts the horizontal plane equal. The time of flight would be given for an angle of 45° by the formula:

_T_ = ¹⁄₄√_X_

In which _T_ represents the time of flight, and _X_ the range expressed in feet. These results are found to answer in practice for projectiles which experience slight resistance from the air, or for heavy projectiles moving with low velocities, as is usually the case with those of mortars and howitzers, for which, within certain limits, the above results are sufficiently accurate in practice.

_Trajectory in Air._--A body moving in air experiences a resistance which diminishes the velocity with which it is animated. Thus it has been shown that certain cannon-balls do not range one-eighth as far in the air, as they would if they did not meet with this resistance to their motion, and small-arm projectiles which have but little mass are still more affected by it. This resistance is expressed by the formula:

( _v_)
_P_ = _A_{p}R_²(1 + ---)_v_²;
( _r_)

in which _P_ represents the resistance in the terms of the unit of weight, _v_ the velocity, and _pR_² the area of a cross-section of the projectile, _A_ the resistance in pounds on a square foot of the cross-section of a projectile moving with a velocity of one foot, _r_ is a linear quantity depending on the velocity of the projectile. For all service spherical projectiles _A_ is .000514, and for all service velocities _r_ is 1.427 feet; the value of _A_ for the rifle-musket bullet is .000358; hence, the resistance of the air is about one-third less on the ogival than on the spherical form of projectile. _A_ being a function of the density of air, its value depends on the temperature, pressure, and hygrometric condition. It has been demonstrated that the final velocity of a projectile falling in the air is directly proportional to the product of its diameter and density, and inversely proportional to the density of the air; the retarding effect of the air is less on the larger and denser projectiles, and for the same caliber an oblong projectile will be less retarded by the air than one of spherical form and consequently with an equal, perhaps less, initial velocity, its range will be greater. It has also been shown that great advantage in point of range is obtained by using large projectiles instead of small ones, solid projectiles instead of hollow ones, leaden projectiles instead of iron ones, and oblong projectiles instead of round ones. The ogival form, or the form of the present rifle-musket bullet, experiences less resistance in passing through the air than any other known. In consequence of the variable nature of the resistance of the air, it has been found impossible to find an accurate expression for the trajectory. Capt. Didion, of Metz, has, however, found an approximate solution; he states that all cases of the movement of a projectile may be divided into three classes: 1st. When the angle of projection is slight or does not exceed 3°, as in the ordinary fire of guns, howitzers, and small-arms,--for slight variations of the angle of projection above or below the horizontal, the form of the trajectory may be considered constant, and when the object is but slightly raised above or depressed below the horizontal plane, it may be considered as in this plane. 2d. When angles of projection do not exceed 10° or 15°, as in the ricochet fire of guns, howitzers, and mortars. 3d. When the angle of projection exceeds 15°, as is the case in mortar fire. For each of these cases he has deduced formulæ, by means of which the range, time of flight, etc., can be determined. As a projectile rises in the ascending branch of its trajectory, its velocity is diminished by the retarding effect of the air, and the force of gravity, in consequence of the resistance of the air alone, the velocity continues to diminish to a point a little beyond the summit of the trajectory, where it is a minimum, and from this point it increases, as it descends, under the influence of the force of gravity, until it becomes uniform, which event depends on the diameter and weight of the projectile, and the density of the air.

The inclination of the trajectory decreases from the origin to the summit, where it is nothing, it increases in the descending branch from the summit to its termination, and if the ground did not interpose an obstacle, it would become vertical at an infinite distance. An element of the trajectory in the descending branch has a greater inclination than the corresponding element of the ascending branch. Strictly speaking, therefore, the trajectory of a projectile in air is not a parabola, but is an exponential curve with two asymptotes, the first the axis of the piece, which is tangent to the trajectory when the initial velocity is infinite, the second a vertical line toward which the trajectory approaches, as the horizontal component of the velocity diminishes and the effect of the force of gravity increases. The curvature of the trajectory increases in the ascending branch to a point a little beyond the summit. The point of greatest curvature is situated nearer the summit than the point of minimum velocity. In the fire of mortar-shells, under great angles of projection, the trajectory may be considered as an arc, in which the angle of fall is slightly greater than the angle of projection. In the formulæ deduced by Didion, in consequence of considering the inclination of the trajectory as constant, the resistance of the air is slightly underestimated in the more inclined portions of the trajectory or at the beginning and end, and slightly overestimated in the less inclined portions or about the summit. It follows that the calculated trajectory will at first rise above the true one, then pass below it and again pass above it; the calculated ranges are therefore slightly in excess of the true ones.

_Trajectory of Oblong Projectiles._--From the law of inertia, a rifle projectile moves through the air with its axis of rotation parallel to the axis of the bore. Hence it follows that an oblong projectile, fired under a low angle of projection, presents a greater surface toward the earth, and less parallel to it, than a round projectile of the same weight, consequently the vertical component of the resistance of the air is greater, and the horizontal component less, in the first case than in the second. The effect of this will be to give an oblong projectile a flatter trajectory and longer range than a round one.

_Deviation of Projectiles._--The path described by the centre of inertia of a projectile, moving under the influences of gravity and the tangential resistance of the air, is called the _normal trajectory_. In practice, various causes are constantly at work to deflect a projectile from its normal path. All deviating causes may be divided into two classes,--those which act while the projectile is in the bore of the piece, and those which act after the projectile has left it. The first class includes all the causes which affect the initial velocity, and give rotation to the projectile; the second includes the action of the air.

_Causes which affect Initial Velocity._--The principal causes which affect initial velocity are variations in the weights of the powder and projectile, the manner of loading, the temperature of the piece, and the balloting of the projectile along the bore. _Rotation._ The principal cause of the deviation of a projectile is its rotation combined with the resistance of the air. _By balloting._ If the projectile be spherical and homogeneous, rotation is produced by the bounding or balloting of the ball in the bore, arising from the windage. In this case the axis of rotation is horizontal, and passes through the centre of the ball; the direction of rotation depends on the side of the projectile which strikes the surface of the bore last. The velocity of rotation from this cause depends on the windage, or depth of the indentations in the bore, the charge being the same. _By eccentricity._ If, from the structure of the ball, or from some defect of manufacture, the centre of gravity does not coincide with the centre of figure, rotation generally takes place around the centre of gravity. This arises from the fact that the resultant of the charge acts at the centre of figure, while inertia, or resistance to motion, acts at the centre of gravity. For the same charge the velocity of rotation passes through the centre of gravity, and is perpendicular to a plane containing the resultant of the charge and the centres of figure and gravity. For the same charge, the velocity of rotation is proportional to the lever arm, or the perpendicular, let fall from the centre of gravity to the resultant of the charge. Knowing the position of the centre of gravity of the ball in the bore, it is easy to foretell the direction and velocity of rotation. In general terms the front surface of the projectile moves toward the side of the bore on which the centre of gravity is situated, and the velocity of rotation is greatest when the line joining the centres of gravity and figure is perpendicular to the axis of the bore.

_The Effect of Rotation._--The effect of rotation in producing deviation may be discussed under three heads: 1st. When the projectile is spherical and concentric; 2d. When it is spherical and eccentric; and, 3d. When it is oblong. If a projectile be spherical and concentric, rotation takes place from contact with the surface of the bore around a horizontal axis, and the effect will be to shorten or lengthen the range, as the motion of the front surface is downward or upward. If the projectile be eccentric, the motion of the front surface is generally toward the side on which the centre of gravity is situated, and the deviation takes place in this direction. The extent of the deviation for the same charge depends on the position of the centre of gravity; the horizontal deviation being the greatest when the centres of gravity and figure are in a horizontal plane, and the line which joins them is at right angles to the axis of the piece; the vertical deviation will be the greatest when these centres are in a vertical plane, and the line which joins them is at right angles to the axis of the piece. If the axis of rotation coincide with the tangent to the trajectory throughout the flight, all points of the surface have the same velocity in the direction of the motion of translation, and there will be no deviation. This explains why it is that a rifle projectile moves through the air more accurately than a projectile from a smooth-bored gun. In accurate firing, therefore, it is important to know the true position of the centre of gravity. In ricochet firing over smooth water, the number of grazes may be increased or diminished by placing, in loading, the centre of gravity above or below the centre of figure.

_Deviation of Oblong Projectiles._--The cause of the deviation of an oblong rifle projectile is quite different from one of spherical form. An oblong projectile moving in the air is acted upon by two rotary forces, viz.: one which gives it its normal rotary motion around its axis of progression, and another the resistance of the air, which, in consequence of the deflection of the axis of progression from the tangent to the trajectory by the action of gravity, does not pass through the centre of inertia, but above or below it; depending on the shape of the projectile. From a law of mechanics, a body thus circumstanced will not yield fully to either of the forces that thus act upon it, but its apex will move off with a slow uniform motion to the right or left of the vertical plane, depending on the relative direction of the two rotary forces. If the action of these forces be continued sufficiently long, it will be seen that the axis of the projectile before referred to describes a cone around a line passing through the centre of inertia and parallel to the direction of the resistance of the air. Owing to the short duration of the flight of an ordinary projectile, it is only necessary to consider the first part of this conical motion. If the projectile rotates in the direction of the hands of a watch to the eye of the marksman, and the resultant of the resistance of the air pass above the centre of inertia, as it does in the service bullet with a conoidal point, then the point of the projectile will move to the right, which brings the left side of the projectile obliquely in contact with the current of the air. The effect of this position with reference to the air will be to generate a component force that will urge the projectile to the right of the plane of fire. This peculiar deviation was called by the French officers that first observed it, “_derivation_,” or “_drift_.”

_Summary of Deviating Causes._--The following summary may be considered as embracing nearly all the causes of deviation of cannon and small-arm projectiles: 1st. _From the construction of the piece._ These causes are, wrong position of the sight; bore not of the true size; windage, etc. 2d. _From the charge of powder._ Improper weight; form of grain and variable quality of the powder, etc. 3d. _From the projectile._ Not of the exact size, shape, or weight; disfiguration in loading, or on leaving the bore; eccentricity. 4th. _From the atmosphere_, _etc._ The effect of wind; variations in the temperature, moisture, and density of the air; position of the sun as regards the effect on the aim; difference of level between the object and the piece; and rotation of the earth. It is found that a projectile will deviate to the right of the object in the northern hemisphere whatever may be the direction of the line of fire, and at a distance from it, depending on the latitude of the place, and on the time of flight and the range of the projectile.

=Projectiles, Effects of.= The effects of projectiles, and particularly that of penetration, depend on the nature of the projectile, its initial velocity, and the distance of the object. The effects of the various kinds of projectiles upon iron and steel plates are not yet thoroughly understood, and experiments are still being made, particularly in England, to determine the best combinations of wrought and cast iron, and steel, to resist the penetration of the enormous projectiles of the present day. Their effects upon wood, earth, etc., are, however, better understood.

_Effect on Wood._--The effect of a projectile fired against wood varies with the nature of the wood and the direction of the penetration. If the projectile strikes perpendicular to the fibres, and the fibres be tough and elastic, as in the case of oak, a portion of them are crushed, and others are bent under the pressure of the projectile, but regain their form as soon as it has passed by them. In consequence of the softness of white pine, nearly all the fibres struck are broken, and the orifice is nearly the size of the projectile; for the same reason the effects of the projectile do not extend much beyond the orifice; pine is therefore to be preferred to oak for structures that are not intended to resist cannon projectiles, as block-houses, etc.

_Effect on Earth._--Earth possesses advantages over all other materials as a covering against projectiles; it is cheap and easily obtained, it offers considerable resistance to penetration, and to a certain extent regains its position after displacement. It is found by experience that a projectile has very little effect on an earthen parapet unless it passes completely through it. Wherever masonry is liable to be breached, it should be masked by earthworks with natural slopes. Gen. Gillmore states that the powers of resistance of pure, compact, quartz sand to the penetration of projectiles very much exceed that of ordinary earth, or mixture of several earths. The size of the openings formed by the passage of a projectile into the earth is about one-third larger than the projectile, increasing, however, towards the outer orifice. Rifle projectiles especially are easily deflected from their course in earth, hence their penetration is variable. Unless a shell be very large in proportion to the mass of earth penetrated, its explosion will produce but little displacement,--generally, a small opening is formed around an exploded shell by the action of the gas in pressing back the earth. Time-fuzes, being liable to be extinguished by the pressure of the earth, are inferior to percussion-fuzes, which produce explosion when the projectile has made about three-fourths of its proper penetration. The penetration in earth of oblong, compared to round projectiles, when fired with service charges, and at a distance of about 400 yards, is at least _one-fourth greater_. This difference, however, is less at short and greater at long distances. The penetrations of similar projectiles into a given substance, are proportional to the squares of the velocities of impact and to the diameters and densities of the projectiles.

_Penetration in Water._--The penetration of a rifle projectile in water depends much on the direction of its axis with respect to penetration; for instance, penetration rapidly diminishes at long distances, as the axis of the projectile strikes the surface of the water under a diminished angle.

_Effect on Masonry._--The effect of a projectile against masonry is to form a truncated conical hole, terminated by another of a cylindrical form. The material in front of and around the projectile is broken and shattered, and the end of the cylindrical hole even reduced to powder. The exterior opening varies from four to five times the diameter of the projectile, and the depth varies with the size and density of the projectile, and its velocity. When a projectile strikes against a surface of oak, as the side of a ship, it will not stick if the angle of incidence be less than 15°, and if it do not penetrate to a depth nearly equal to its diameter. Solid cast-iron shot break against granite, but not against freestone or brick. Shells are broken into small fragments against each of these materials.