Part 114

=Ricochet.= In gunnery, the repeated rebounding of round-shot. By firing at a slight elevation, with small charges, in a direction enfilading the face of a work, shot are pitched over the parapet, and bound along the rampart from end to end, with most destructive effect on the guns and gunners occupying it.

=Ricochet Battery.= See BATTERY.

=Ricochet Firing.= See FIRE, RICOCHET.

=Rideau.= Is a rising ground, or eminence, commanding a plain, sometimes almost parallel to the works of a place. It is a great disadvantage to have rideaus near a fortification, which terminate on the counterscarp, especially when the enemy fire from afar; they not only command the place, but facilitate the enemy’s approaches.

=Rider.= In artillery carriages, a piece of wood, which has more height than breadth; the length being equal to that of the body of the axle-tree, upon which the side-pieces rest in a four-wheel carriage, such as the ammunition-wagon, block-carriage, and sling-wagon.

=Ridge.= In fortification, is the highest part of the glacis proceeding from the salient angle of the covered way.

=Riding-Master.= In the British service, in cavalry, artillery, and the army service corps, is an officer whose duty it is to instruct the officers and men in the management of their horses. He is most commonly selected from the ranks. The riding-master has the relative rank of lieutenant, and, after an aggregate service of thirty years, including at least fifteen years as riding-master, he has the right to retire on 10 shillings a day, with the honorary rank of captain. He is assisted in his duties by rough riders. (See ROUGH RIDER.)

=Riff, The.= A portion of the coast of Morocco which extends from Tangier on the west, to near the western frontier of Algeria. The name in the Berber language, which is that of the inhabitants, signifies a mountainous and rugged coast. The inhabitants of the Riff were formerly engaged in piracy. On account of the injuries inflicted by them on merchant vessels, most of the maritime states of Europe agreed to pay an annual sum of quit-money. However, in 1828, Austria declined further payment of the tax. A Venetian vessel was seized by the pirates in the harbor of Rabat, but the arrival of an Austrian fleet off the port produced restitution of the ship and its cargo, as well as the formal renunciation of all further claims. France followed the same course by declaring war against the sultan of Morocco, and obtained compensation in 1844, since which period piracy has much diminished. Its example was followed by the Spaniards in 1859.

=Rifle.= A fire-arm having a number of spiral grooves cut into the surface of its bore, for the purpose of giving the projectile a motion about a line coinciding with the direction of its flight. See ORDNANCE, SMALL-ARMS, MAGAZINE GUNS, and LYMAN’S MULTI-CHARGE GUN.

=Rifle Projectile.= See PROJECTILE.

=Rifled Cannon=, or =Rifle-cannon=. A cannon of which the bore is rifled.

=Rifled Musket.= A musket of which the bore is rifled.

=Riflemen.= A peculiar kind of light infantry, consisting of experienced marksmen, armed with the most improved rifles. In the British army there are two battalions of the rifle brigade and of the 60th Rifles, the Ceylon Rifles, and the Cape Mounted Riflemen.

=Rifle-pit.= A pit dug for the shelter of sharpshooters.

=Rifling.= The yielding nature of lead renders the application of the rifle principle of easy accomplishment in the case of rifle-muskets, but such is not the case with rifle-cannon where the projectiles are made of iron. The object of the most recent experiments is to determine the safest and surest means of causing the projectile to follow the spiral grooves as it passes along the bore of a rifled piece. For description of the manner of doing this, see PROJECTILE.

_Form of Groove._--The form of a rifle groove is determined by the angle which the tangent at any point makes with the corresponding element of the bore. If the angles be equal at all points the groove is uniform. If they increase from the breech to the muzzle, the grooves are called increasing; if the reverse, decreasing. The inclination of a rifle groove at any point is measured, accurately, by the tangent of the angle which it makes with the axis of the bore, which is always equal to the circumference of the bore divided by the length of a single revolution of the spiral, measured in the direction of the axis. Grooves are of two kinds,--_uniform_ and _variable_.

_Uniform Groove._--The comparative advantages of uniform and variable grooves depend on the means used to connect them with the projectiles. If the bearing of the projectile in the grooves be long, and the metal of which it is made be unyielding, it will be unsafe, if not impracticable, to employ variable grooves, and if the metal be partially yielding, a portion of the force of the charge will be expended in changing the form of that part of the projectile which projects into the grooves, as it moves along the bore.

_Variable Groove._--The variable groove may be used to advantage when the portion of the projectile in the grooves is so short that its form will undergo but slight alteration; the variable groove diminishes the friction of the projectile when it is first set in motion, and thereby relieves the breech of the piece of a portion of the enormous strain which is thrown upon it. If the twist be too rapid towards the muzzle there will be danger of bursting the piece in the chase.

_Width of Groove._--The width of a groove depends on the diameter of the bore and the peculiar manner in which the groove receives and holds the projectile. Wide and shallow grooves are more easily filled by the expanding portion of the projectile than those which are narrow and deep; and the same holds true of circular-shaped grooves when compared to those of angular form.

_Number of Grooves._--An increase in the number of grooves increases the firmness with which a projectile is held, by adding to the number of points which bear upon it. A large number of grooves, however, increase the difficulties of loading. For expanding projectiles an odd number of grooves is generally employed, for as this places a groove opposite to a land, less expansion will be required to fill them.

_Inclination of Grooves._--Experience has shown that, as the velocity of rotation depends upon the form and initial velocity of the projectile, the causes which retard it, and the time of flight, there is a particular inclination of grooves which is best suited to each caliber, form of projectile, charge of powder, and angle of fire. The farther the centre of gravity of a projectile is in rear of the centre of figure, or resistance of the air, the greater must be the inclination of the grooves to resist deviation. It therefore follows that a conical projectile of the same length and diameter, requires a greater inclination of grooves than a cylindrical projectile, and the same will hold true for other forms as they approach one or the other of these extreme cases. The friction of the projectile as it passes along the grooves, increases with their inclination; its effect will be to diminish the range and increase the strain on the piece, and the inclination may be carried so far as to break the projectile, or rupture the piece.

_Centring._--In consequence of the windage necessary in all muzzle-loading guns, the axis of the projectile does not always coincide with that of the bore in firing. This leads to inaccuracy of fire. A projectile is said to be centred when the grooves of the rifling are so constructed as to bring the axis of the projectile on a line with that of the bore when the piece is fired. There are several ways of accomplishing this, among them Armstrong’s method called “Shunt rifling.” See ARMSTRONG GUN under ORDNANCE, CONSTRUCTION OF, the KRUPP, and others.

=Riga.= An important seaport of Russia, capital of Livonia, on the Düna, 312 miles southwest from St. Petersburg. Riga was founded in the beginning of the 13th century. The Teutonic Knights possessed it in the 16th century. In 1621 it was taken by Gustavus Adolphus, and in 1710, after a vigorous resistance, by Peter the Great. On the latter occasion more than half of the town was destroyed. In 1812 a French force was repulsed from the town.

=Rigodon= (_Fr._). Formerly a beat of drum while men who were shelled (a French punishment, the severest next to death) were paraded up and down the ranks previous to their being sent to their destination.

=Rimbases.= In gunnery, are short cylinders uniting the trunnions with the body of the gun. The ends of the rimbases, or the _shoulders_ of the trunnions, are planes perpendicular to the axis of the trunnions. Rimbases are for the purpose of strengthening the trunnions at their junction with the piece, and by forming shoulders, to prevent the piece from moving sideways in the trunnion-beds.

=Rimer.= A palisade in fortification.

=Rimini= (anc. _Ariminum_). A city of Central Italy, on the Adriatic Sea, about 28 miles east-southeast from Forli. It was founded by the Umbri; was conquered by the Romans; sacked by Sulla; plundered and destroyed several times by the barbarians; then given by Charlemagne to the church.

=Rimnik.= A town of Wallachia, on the Rimnik, 66 miles northeast from Bucharest. Here the Austrians and Russians, under Prince Coburg and Gen. Suwarrow, gained a great victory over the Turks, September 22, 1789.

=Ring-armor.= Armor composed of rings of metal.

=Ringleader.= The leader of a ring; especially, the leader of an association of men engaged in violation of law or an illegal enterprise, as rioters, mutineers, and the like.

=Ring-mail.= A kind of mail composed of small rings of steel sewed edgewise upon a strong garment of leather or of quilted cloth.

=Ring-wads.= See GROMMET.

=Rio Janeiro=, or =Rio de Janeiro=, often called simply Rio. The capital of Brazil, and the largest and most important city of South America. The harbor, which is strongly fortified, is one of the best in the world, and large enough for all its navies. The city of Rio was founded by the Portuguese in 1567. In 1831, it was the theatre of a revolution, in which 6000 armed citizens were joined by the troops of the line in their opposition to the government, and in consequence of which Dom Pedro abdicated the throne in favor of his son Pedro II.

=Riot and Tumult.= Sedition, civil insurrection, disturbance, etc. A breach of the peace committed by an assembled multitude. Some degree of violence is incidental to a riot, and a degree of intimidation to the neighborhood. According to law a riot cannot take place unless three persons act in concert. When a riot becomes formidable, it is usual for the authorities to take active measures to disperse it.

=Rioters.= Disturbers of the public peace; persons acting in open violation of good order; raising or creating sedition, etc.

=Ripon.= An ancient town of England, in Yorkshire, 23 miles northwest of York. It suffered much by the ravages of the Danes and the Normans (1069), and the Scots (1319 and 1323).

=Risban= (_Fr._). In fortification, a flat piece of ground upon which a fort is constructed for the defense and security of a port or harbor. It likewise means the fort itself.

=Risberme= (_Fr._). A work composed of fascines, such as is sometimes constructed at the bottom of a town-wall. A sort of glacis of fascine-work used in jetties, the sides of which, towards the sea, are so formed as to withstand its violence.

=Rise.= In a military sense, is to make hostile attack; as, the soldiers rose against their officers. It also means to obtain promotion. _To rise from the ranks_, is to obtain a commission by degrees, after having been in the ranks as a private soldier.

=Rising.= In heraldry, a term applied to a bird when represented opening his wings as if about to take flight.

=Riveting-plates.= In gun-carriages, are small, square, thin pieces of iron, through which the ends of the bolts pass, and are riveted upon them.

=Rivoli.= A town of Italy on the right of the river Dora, and 8 miles west of Turin. It possesses a royal castle, which was sacked by the French in 1690. In 1797 a battle was fought here between the French and Austrians, in which the former were victorious.

=Rizamedar.= In the East Indies, is an officer commanding a small body of horse.

=Roanoke.= A river of Virginia and North Carolina; empties into Albemarle Sound. In 1861, Albemarle Island, at its mouth, and Plymouth were taken by the Federal gunboats.

=Robinet.= An ancient military machine for throwing darts and stones.

=Rochelle, La.= A fortified seaport of France, capital of the department of Charente-Inférieure, on an inlet of the Bay of Biscay, 300 miles southwest of Paris by railway. It was taken from the English by the troops of the French king Louis XIII. in 1224; was ceded to England at the treaty of Bretigny in 1360; in the subsequent wars it was retaken by France, under whose sway it has remained since 1372. As a stronghold of the Huguenot party, it underwent various attacks and sieges during the religious wars of the Henries, in the latter half of the 16th century; and on its final and unconditional surrender to the royal troops in the time of Louis XIII., its old fortifications were destroyed, and new lines of defenses subsequently erected by the great Vauban.

=Rock Island.= An island in the Mississippi River, the southern extremity of which is nearly opposite the town of Rock Island, Ill. This island is about 3 miles in length, and presents a perpendicular front of limestone 20 or 30 feet high. During the Blackhawk war a garrison was kept on Rock Island, and a part of it was used during the late civil war (1861-65) as a military prison. The U. S. government has a splendid arsenal and armory here.

=Rocket.= A rocket is a projectile which is set in motion by a force residing within itself; it therefore performs the twofold function of piece and projectile. See PYROTECHNY.

_History._--Rockets were used in India and China for war purposes before the discovery of gunpowder; some writers fix the date of their invention about the close of the 9th century. Their inferior force and accuracy limited the sphere of their operations to incendiary purposes, until the year 1804, when Sir William Congreve turned his attention to their improvement. This officer substituted sheet-iron cases for those made of paper, which enabled him to use a more powerful composition; he made the guide-stick shorter and lighter, and removed a source of inaccuracy of flight by attaching the stick to the centre of the base instead of the side of the case. The advantages claimed for rockets over cannon are, unlimited size of projectile, portability, freedom from recoil, rapidity of discharge, and the terror which their noise and fiery trail produce on mounted troops.

_Structure._--A rocket is essentially composed of a strong case of paper or wrought iron, inclosing a composition of nitre, charcoal, and sulphur,--the same as gunpowder, except that the ingredients are proportioned for a slower rate of combustion. If penetration and range be required, its head is surmounted by a solid shot; if explosion and incendiary effect, by a shell or spherical case-shot, to which is attached a fuze, which is set on fire when it is reached by the flame of the burning composition. The base is perforated by one or more vents for the escape of the gas generated within, and sometimes with a screw-hole to which a guide-stick is fastened.

_Motion._--A rocket is set in motion by the reaction of a rapid stream of gas escaping through its vents. If it be surrounded by a resisting medium, the atmosphere, for instance, the particles of gas as they issue from the vent will impinge against and set in motion certain particles of air, and the force expended on the inertia of these particles will react and increase the propelling force of the rocket. It follows, therefore, that, though a rocket will move _in vacuo_, its propelling force will be increased by the presence of a resisting medium. Whether the effect will be to accelerate the rocket depends upon the relation between the resistance which the medium offers to the motion of the gas and that which it offers to the motion of the rocket.

_Vent._--As the rate of combustion of the composition is independent of the pressure of the gas in the bore, it follows, that if the size of the vent be contracted, the flow of gas through it will be accelerated. The strength of the case, and the friction of the gas, which increases as the vent diminishes, alone limit the reduction of the size of the vent. For vents of the same size, but of different shapes, that one which allows the gas to escape most freely will be most favorable to the flight of the rocket. A conical form of vent, with the larger orifice next to the bore, will allow the gas to escape more rapidly than one of cylindrical form.

_Bore._--As the composition of a rocket burns in parallel layers of uniform thickness, the amount of gas generated in a given time, or the velocity of its exit from the case, depends on the extent of the inflamed surface. Experience shows that to obtain the required surface of inflammation, it is necessary to form a long cavity in the mass of the composition. This cavity is called the bore. In all rockets the bore should be concentric with the case; its shape should be made conical to diminish the strain on the case near its head, by reducing the amount of surface where the pressure on the unit of surface is greatest.

_Nature of Movement._--Suppose the rocket in a state of rest, and the composition ignited; the flame immediately spreads over the surface of the bore, forming gas which issues from the vent. The escape is slow in the first moments, as the density of the gas is slight; but as the surface of inflammation is large compared to the size of the vent, the gas accumulates rapidly, and its density is increased until the velocity of the escape is sufficient to overcome the resistance which the rocket offers to motion. These resistances are, inertia, friction, the component of weight in the direction of motion, and, after motion takes place, the resistance of the air. The constant pressure on the head of the bore accelerates the motion of the rocket until the resistance of the air equals the propelling force; after this, it will remain constant until the burning surface is sensibly diminished. When the gas ceases to flow, the rocket loses its distinctive character, and becomes, so far as its movement is concerned, an ordinary projectile. The increase in the surface of combustion whereby more gas is developed in the same time, and the diminution in the weight of the remaining composition, cause the point of maximum velocity to be reached with increased rapidity. If the weight of the rocket be increased, the instant of maximum velocity will be prolonged, but the amount will remain the same. A change in the form of the rocket which increases the resistance of the air, will have the effect to diminish the maximum velocity.

_Guiding Principle._--The propelling force of a rocket changes its direction with the axis along which it acts; it follows, therefore, that without some means of giving stability to this axis, the path described will be very irregular, so much so, at times, as to fold upon itself; and instances have been known where these projectiles have returned to the point whence they started. The two means now used to give steadiness to the flight of a rocket are, rotation, as in the case of a rifle-ball, and the resistance of the air, as in an arrow.

_Hale’s System._--The first is exemplified in Hale’s rocket, where rotation is produced around the long axis by the escape of the gas through five small vents situated obliquely to it. In his first arrangement, the inventor placed the small vents in the base, surrounding the central vent, so that the resultant of the tangential forces acted around the posterior extremity of the axis of rotation. In 1855, this arrangement was changed by reducing the number of the small vents to three, and placing them at the base of the head of the rocket. The rocket thus modified is the one now used by the U. S. government for war purposes. A still later improvement in Hale’s rocket consists in screwing a cast-iron piece into the bottom of the case, which is perforated with three vents. A corresponding side of each vent is surrounded with a fence, the opposite sides being open. The gas in its efforts to expand after issuing from the vents, presses against the fences and rotates the rocket around its long axis.

_Congreve’s System._--A Congreve rocket is guided by a long wooden stick attached to its base. If any cause act to turn it from its proper direction, it will be opposed by resistances equal to its moment of inertia and the lateral action of the air against the stick. The effect of these resistances will be increased by placing the centre of gravity near the head of the rocket, and by increasing the surface of the stick. In signal-rockets, where the case is made of paper, the stick is attached to the side, and there is but one large vent, which is in the centre of the case. In war-rockets the stick is attached to the centre of the base, and the large central vent is replaced by several small ones near its circumference. The former arrangement is not so favorable to accuracy as the latter, inasmuch as rotation will be produced if the force of propulsion and the resistance of the air do not act in the same line.

_How Fired._--Rockets are generally fired from tubes or gutters; but should occasion require it, they may be fired directly from the ground, care being taken to raise the forward end by propping it up with a stick or stone. As the motion is slow in the first moments of its flight, it is more liable to be deviated from its proper direction at this time than any other; for this reason the conducting-tube should be as long as practicable.