Part 107

_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.

_Breaching._--Formerly stone projectiles were much used for breaching, but from the want of sufficient hardness in these projectiles, the besiegers were forced to commence battering at the top of the wall where the least resistance was offered, and gradually to lower the shot until the breach reached the wrecks already formed at the base of the wall. Iron projectiles superseded stone, and then more rapid modes of effecting a practicable breach were suggested. The easiest manner of making the cut is to direct the shots upon the same line, and form a series of holes a little greater than a diameter apart, and then to fire a second series of shots, directed at the intervals between the first, and so on, until an opening is made completely through the wall. If the portion of the wall between the vertical cuts should not be overthrown by the pressure of the earth behind, it must be detached by a few volleys of solid shot, fired at its centre.

_Breaching with Rifle-cannon._--The foregoing has reference particularly to breaching masonry with smooth-bored guns. The same principle is applicable to rifled guns, the only difference being that, from their superior penetration and accuracy, the latter are effective at much longer distances. The most destructive projectile against masonry is the elongated percussion shell.

_Effect of Bullets._--From experiments made in Denmark, the following relations were found between the penetration of a bullet in pine and its effects on the body of a living horse, viz.: 1st. When the force of the bullet is sufficient to penetrate 0.31 inch into pine, it is only sufficient to produce a slight contusion of the skin. 2d. When the force of penetration is equal to 0.63 inch, the wound begins to be dangerous, but does not disable. 3d. When the force of penetration is equal to 1.2 inch, the wound is very dangerous. A plate of wrought iron three-sixteenths of an inch thick, is sufficient to resist a rifle-musket bullet at distances varying from 20 to 200 yards. Iron of thickness, however, will not resist bullets of the present day. That a rope mantlet may give full protection against rifle-musket bullets, it should be composed of five layers (three vertical and two horizontal) of 4¹⁄₂-inch rope.

=Projection.= In mathematics, the action of giving a projectile its motion. It is also used to signify a scheme, plan, or delineation.

=Proking-spit.= A large Spanish rapier.

=Prolongation.= An extension of leave of absence, or a continuation of service.

=Prolongation of the Line.= Is effected by parallel movements at the right or left of any given number of men on a front division.

=Prolonge.= See IMPLEMENTS.

=Prolonge-hooks.= See ORDNANCE, CARRIAGES FOR, NOMENCLATURE OF ARTILLERY CARRIAGE.

=Promotion.= This word signifies, in military matters, the elevation of an individual to some appointment of greater rank and trust to the one he holds.

=Promulgation.= The act of promulgating; publication; open declaration; as, the promulgation of the sentence of a court-martial.

=Proof.= A term applied to the testing of powder, and also of ordnance, which are always fired with a regulated charge of powder and shot, to test their strength and soundness.

=Proof.= Conclusive evidence.

=Proof.= Capable of withstanding; as, bomb-proof, shot-proof.

=Propel.= To drive forward; to urge or press onward by force; to move or cause to move; balls are _propelled_ by the force of gunpowder.

=Proper.= A term which serves to mark out a thing more especially and formally. Thus, the _proper form of a battalion_ is the usual continuity of line given to the formation of a battalion, and which remains unaltered by the wheelings of its divisions; or if altered, is restored by the same operation. _Proper right_, is the right of a battalion, company, or subdivision, when it is drawn up according to its natural formation. _Proper pivot flank_, in column, is that which, when wheeled up to, preserves the division of the line in the natural order, and to their proper front. The other may be called the _reverse_ flank.

=Proper.= In heraldry, a charge borne of its natural color, is said to be _proper_. An object whose color varies at different times and in different examples, as a rose which may be white or red cannot be borne proper.

=Prosecute.= To carry on; to continue; as, to prosecute the war. Also, to accuse of some crime or breach of law, or to pursue for punishment before a legal tribunal; to proceed against judicially.

=Prosecutor.= In courts-martial the judge-advocate is usually the prosecutor; but if an officer prefers a charge, he sometimes appears to sustain the prosecution. No person can appear as prosecutor not subject to the articles of war, except the judge-advocate.--_Hough._

=Proveditor.= One employed to procure supplies for an army; a purveyor.

=Proving-ground.= Ground used for testing powder or ordnance.

=Provision.= Properly to victual; to furnish with provisions.

=Provost.= The temporary prison in which the military police confine prisoners till they are disposed of.

=Provost Cells.= Also called regimental or garrison cells, in the British service are those certified cells under a provost or acting provost-sergeant, in which court-martial prisoners may be imprisoned up to forty-two days.

=Provost-Marshal.= In the army, is an officer appointed to superintend the preservation of order, and to be, as it were, the head of the police of any particular camp, town, or district. He has cognizance of all camp-followers, as well as members of the army. His power is summary, and he can punish an offender, taken _flagrante delicto_, on the spot, according to the articles of war.

=Provost-Sergeant.= Is a sergeant who is charged with the military police of a corps. He is generally given one or two non-commissioned officers as assistants. In the British service he also is charged with the custody of all prisoners in the cells.

=Prowess.= Valor; bravery in the field; military gallantry.

=Prowlers.= Are persons who steal within the lines of a hostile army for the purpose of robbing, killing; or destroying bridges, roads, mails, or other means of communication. Such persons are not entitled to the privileges usually accorded to prisoners of war.

=Prussia.= A kingdom of the new German empire. The people of Prussia first appear in history in the 10th century, under the name of Borussi; from these the country derives its name. Some historians, however, derive the name from _Po_, signifying near, and _Russia_. The Prussians were subjected by Boleslaus of Poland in 1018; they made a successful stand against Boleslaus IV. of Poland in 1161, and for a time maintained a rude and savage kind of independence. The Teutonic Knights were engaged in war for half a century with the people,--winning lands and souls by hard fighting,--until at length, in 1283, they found themselves undisputed masters of the country, having almost exterminated the pagan population. During this period the knights founded many cities and repeopled the country with German colonists. In 1454 the municipal and noble classes, with the co-operation of Poland, rose in open rebellion against the knights, who were forced to cede West Prussia and Ermland to Poland. Albert (or Albrecht) of Brandenburg was acknowledged duke of East Prussia in 1525; his son-in-law, John Sigismund, created elector of Brandenburg and duke of Prussia in 1608. The reign of John Sigismund’s successor, Georg-Wilhelm (1619-1640), was distracted by the miseries of the Thirty Years’ War, and the country was alternately the prey of Swedish and imperial armies. The electorate was raised by the genius of Frederick William, the great elector, to the rank of a great European power. His successor, Frederick III. (1688-1713), was proclaimed king of Prussia by the title of Frederick I. in 1701. During the reign of Frederick William IV., Prussia co-operated powerfully in putting down the insurrections in Poland and Baden. In the war of the Schleswig-Holstein duchies, the Prussians acted in concert with the disaffected against their sovereign, the king of Denmark, occupying the ducal provinces in the name and on behalf of the diet. A treaty of peace was concluded between Prussia and Denmark, on July 2, 1850. In 1863 the allied Prussian and Austrian armies entered the duchies of Schleswig-Holstein and defeated the Danes; the duchies were separated from Denmark. Warm disputes with Austria respecting Schleswig-Holstein arose in the beginning of 1866. The vote of the majority of the diet of the Germanic Confederation supported Austria; Prussia announced her withdrawal from the confederation, and its dissolution; the diet declared itself indissoluble, and continued its functions, June 14, 1866. War was declared by Prussia, June 18, 1866, which ended in the total defeat of Austria and her allies. A treaty of peace between Austria and Prussia was signed at Prague on August 23, 1866. By its articles Austria consented to the breaking up of the Germanic Confederation, and to Prussia’s annexing Hanover, Hesse-Cassel, Nassau, and Frankfort-on-the-Main, and gave up Holstein and her political influence in North Germany. For further history, see FRANCO-PRUSSIAN WAR.

=Pruth.= A river of Europe, which rises in the Carpathian Mountains. It forms a portion of the boundary-line between Russia and Turkey, and by crossing it, in 1853, the Russians gave rise to the war with Turkey and the subsequent Crimean war.

=Psiloi.= Among the Greeks, were light-armed men who fought with arrows and darts, or stones and slings, but were unfit for close fight. They were in honor and dignity inferior to the heavy-armed soldiers.

=Publish.= To make known. In a garrison orders are published by being read at parade. Orders are also published by circulating written copies.

=Puebla=, or =La Puebla de los Angeles=. Capital of the department of Puebla, in Mexico, 80 miles southeast from the city of Mexico. It was taken by the French on May 17, 1863, after a siege of several weeks’ duration, the Mexican general Ortega, with 18,000 men, surrendering to Gen. Forey. This event threw open the road to Mexico, and was the immediate precursor of the overthrow of the government of Juarez.

=Pueblo Indians= (Sp. _pueblo_, “village”). An interesting class of semi-civilized Indians in New Mexico and Arizona, so called from their remarkable residences, a description of some of which may be found under MOQUIS INDIANS. They are divided into several tribes speaking different languages. Their internal administration is patriarchal, each pueblo or village being ruled by its governor and council of three elders.

=Pulk.= A tribe; a particular body of men. This word is chiefly used in Russia; as, a pulk of Cossacks.

=Pultowa.= See POLTAVA.

=Pultusk.= A town of Poland in the government of Plock, situated on the Narew, 35 miles north-northeast from Warsaw. Here on December 26, 1806, was fought one of the battles of the campaign of Eylau, between the Russians and the French. The field was most obstinately contested, but the victory, which, however, was claimed by both armies, inclined in favor of the French.

=Pummel.= The hilt of a sword, the end of a gun, etc.

=Puncto.= The point in fencing.

=Punic Wars.= The name of three celebrated contests, in which the Romans and Carthaginians were engaged from the year 264 to 146 B.C., and which finally terminated with the destruction of Carthage. It was in the second war, which began in 218, that the Carthaginian commander Hannibal rendered himself so distinguished by his victories over the Romans. The illustrious Scipio was eventually the conqueror of Hannibal and the victor of Carthage. _Punic faith_ is a reproachful term in frequent use, derived from _Punici_, or Carthaginians, because they were considered by the Romans a perfidious race.