Chapter XL: Part 40

_Palliser Gun._--Maj. Palliser of the British service is the inventor of a system which has been successfully applied in England to utilize smooth-bore cast-iron guns by converting them into rifles. By his plan the gun is first bored to a cylinder or finely tapering cone, then lined with a tube of coiled wrought iron, the breech end of which is shrunk on; the exterior of the barrel has a uniform diameter throughout. The tube is double at this part to obtain the benefit of the tension and to enable any fracture of the inner layer to be made known without bursting the gun. The bottom of the barrel is closed by a wrought-iron cup screwed in. The tube is inserted into the gun from the muzzle without the application of heat. A small amount of play is allowed between the barrel and the cast-iron body; this disappears, or is much reduced by a “setting up charge,” which expands the barrel against the cast iron. The end of the barrel is made to bear accurately against the cast-iron breech. A collar screwed into the muzzle secures the tube in position, and prevents it from being thrust forward by the compression of the metal by repeated firing. In front of the trunnions a pin is screwed in through the cast iron, to resist the tendency of the tube to be turned by the bearing of the projectile in the grooves. On the exterior of that portion of the inner tube that is covered by the second tube is cut a spiral gas channel; this communicates with a tell-tale hole drilled through the cast-iron breech, by which gas can escape and announce the fracture of the inner tube. The venting and rifling are similar to those employed in the Woolwich guns. In the larger guns Maj. Palliser proposes to use two or more concentric tubes, in some the exterior one to be of steel. This system is being applied in the United States with the most promising results in the conversion of 10-inch Rodman guns into 8-inch rifles. The rifles thus obtained, though giving to a projectile a less muzzle velocity than does the 10-inch smooth-bore, has, on account of the increased weight of shot, greater penetrating power at all ranges, being doubled at some and trebled at others. Its accuracy is three times greater, and the capacity of its shell twice that of the original gun.

_Parsons Gun._--The system upon which Mr. Parsons makes his guns is similar to that of Maj. Palliser. (See PALLISER GUN.) It depends upon the principle of varying elasticities, and is based upon the fact that wrought iron may be stretched three times as much as cast iron, and will offer three and a half to six times the resistance within the limit of its elasticity. These well-known gun constructions, known as _converting systems_, both consist in lining a cast-iron case with a wrought-iron or steel tube. In the Palliser or English method the tube is inserted from the muzzle. In the Parsons or American method, through the breech. In both nearly the whole of the longitudinal strain is transferred to the cast-iron case. Both systems were first perfected in England. Col. Crispin (U. S. Ordnance Corps) deserves the credit of introducing them into the U. S. service in constructing the new _experimental rifles_. The Parsons system is better adapted to constructing breech-loaders.

_Parrott Gun._--The Parrott rifled gun is a cast-iron piece of about the usual dimensions, strengthened by shrinking a coiled band or barrel of wrought iron over that portion of the reinforce which surrounds the charge. The body of the larger Parrott guns are cast hollow, and cooled from the interior on the Rodman plan. The barrel is formed by bending a rectangular bar of wrought iron spirally around a mandrel, and then welding the mass together by hammering it in a strong cast-iron cylinder, or tube. In bending the bar, the outer side being more elongated than the inner one, is diminished in thickness, giving the cross-section of the bar a wedge shape, which possesses the advantage of allowing the cinders to escape through the opening, thereby securing a more perfect weld. The barrel is shrunk on by the aid of heat, and for this purpose the reinforce of the gun is carefully turned to a cylindrical shape, and about one-sixteenth of an inch to the foot larger than the interior diameter of the barrel in a cold state. To prevent the cast iron from expanding when the barrel is slipped on to its place, a stream of cold water is allowed to run through the bore. At the same time, and while the band hangs loosely upon it, the body of the gun is rotated around its axis to render the cooling uniform over the whole surface of the barrel. The proof of the Parrott guns consists in firing each piece 10 rounds with service charges.

_Rodman Gun._--The principal difficulty formerly experienced in manufacturing very large cast-iron cannon was the injurious strain produced by cooling the casting from the exterior. Gen. Rodman of the U. S. Ordnance Department developed a theory of the strains produced by cooling a casting like that of a cannon (see ORDNANCE, STRAINS UPON), and as a remedy for them proposed that cannon should be cast on a hollow core and cooled by a stream of water or air passing through it. This new mode of casting was afterwards adopted by the War Department. By this system of casting, guns of greatly increased size and endurance are fabricated. The largest guns employed in the U. S. service (20-inch) are made on the Rodman plan, as well as many of the guns employed in the field service.

_Whitworth Gun._--These guns are made of a species of low steel; the smaller are forged solid, the larger are built up with coils or hoops; the hoops are forced on by hydraulic pressure, and for this purpose are made with a slight taper and with the design to secure initial tension. The ends of the hoops are joined by screw-threads. The hoops are first cast hollow, and then hammered out over a steel mandrel. Before receiving their final finish they are subject to an annealing for some three or four weeks, which makes the metal very ductile, but at the same time slightly impairs its tenacity. The system differs from Krupp’s in the smaller masses used and the greater number of hoops. The process for making the hoops is better calculated to develop their tensile strength. The breech-pin is made with offsets in such a way as to screw into the end of the barrel and the next two surrounding hoops. The cross-section of the bore of the Whitworth gun is a hexagon with rounded corners. The twist is very rapid and the projectiles are made very long.

_Woodbridge Gun_ (invented by Dr. Woodbridge, of Little Falls, New York).--The system of construction consists essentially of a thin steel barrel over which wire is wound, barrel and wire being subsequently consolidated into one mass by a brazing solder melted and poured into the interstices. The following brief description is extracted from one of the inventor’s letters to the chief of ordnance: “Square wire is wound upon a steel core somewhat longer than the intended bore of the gun, a sufficient number of wires being wound at once side by side to produce the required obliquity of the turns. The successive layers have opposite twists. When the mass has reached the required dimensions, it is inclosed in an air-tight case to protect it from oxidation, and is heated therein to a temperature somewhat above that required for the fusion of the soldering metal. The soldering metal having been melted is run in, filling all the interstices of the mass. When cooled the gun is bored and finished as usual.” The invention dates back to about 1850. A small gun made in this way was tested by Maj. Laidley (U. S. Ordnance Corps) in 1865. It endured 1327 rounds with excessive charges, when the attempt to burst it was abandoned on account of the breaking off of the trunnions. The only large gun ever made--a 10-inch gun--was fabricated at Frankford Arsenal. It was not entirely finished till April, 1876, soon after which it was displayed at the Centennial Exhibition in Philadelphia. Certain defects in its manufacture prevent it from fairly representing the Woodbridge system.

_Woolwich Gun._--The Woolwich or Fraser gun is in its construction a modification of the Armstrong plan, which latter had been previously used in Great Britain; the principal difference is in substituting for a number of single coils and a forged breech-piece a few long double and triple coils, and in using a cheaper quality of wrought iron. The number of pieces employed in the construction depends upon the size of the gun; an 8-inch rifled gun is composed of the inner tube (barrel) of steel, the muzzle-coil (trousers), the breech-coil (jacket), and the cascabel-screw. The barrel is made from a solid forged cylinder of cast steel, drawn by heating and hammering; it is turned, bored, and chambered; then heated to a uniform temperature in a vertical furnace and plunged into a covered tank of rape-oil, where it cools and soaks. The muzzle-coil is constructed of two single coils welded together endways. Each coil is formed by heating a long bar and wrapping it about a mandrel; this is next heated in a reverberatory furnace and welded under a steam-hammer. Before being united the two cylinders are turned and bored. The breech-coil is composed of a triple coil, a trunnion-ring, and a double coil welded together. The double coil is formed by placing a single coil, when cold, on a mandrel and winding over it, but in the reverse directions to break joints, a second bar; if over this a third bar is immediately wound in the same direction as the first, a triple coil will result. These coils are welded by being heated and hammered on the end and on the sides. The trunnion-ring is made by welding slabs of iron together on the flat end of a bar, and gradually forming a ring by driving through the centre wedges and mandrels increasing in size; the trunnions, one of which comes from the bar, are at the same time hammered into shape. The coils and the ring having been turned and bored, the latter is placed on a shoulder of the triple coil, the double coil is dropped through the trunnion-ring on the triple coil, and the joints welded in this position. The cascabel is forged of good scrap-iron; the different parts having been formed are accurately turned and bored with a slight taper. The muzzle-coil tube being heated is dropped over the barrel, which is stood in a pit, a stream of cold water circulating through the bore. The half-formed gun is then placed on its muzzle, water forced through the bore, and the breech-coil heated and slipped into position. The cascabel is screwed into the breech-coil abutting against the barrel, great care being taken that the contact is perfect. A tell-tale hole is cut along the thread on the cascabel to give warning by the escape of gas should the barrel break in firing. The vent is bored through hardened copper; it enters near the centre of the service cartridge. This gives greater velocity, but also greater pressure. The large guns have from seven to ten grooves. The twist is uniformly increasing; the shape of the grooves is circular, with curved edges.

_Sutcliffe Gun._--This invention, by E. A. Sutcliffe of New York City, relates to a breech-mechanism for cannon. See BREECH MECHANISM.

_Griffin Gun._--Name sometimes given to the 3-inch rifled field-piece in the U. S. service. It is made of wrought iron. The method of fabrication is to wrap boiler-plate around a mandrel and to weld it.

=Ordnance, Metals for.= The only metals ordinarily used for cannon are cast and wrought iron, steel, and an alloy of copper and tin, or a combination of these metals. Cannon metals should be able to resist the corroding action of the atmosphere, the heat and the products of combustion of the powder; should be susceptible of being easily bored and turned, and should not be too costly. The qualities necessary in cannon metals are strength to resist the explosion of the charge, weight to overcome severe recoil, and hardness to endure the bounding of the projectile along the bore. The shape of the bore would otherwise be rapidly altered by the action of the projectile. This quality is particularly necessary in rifled cannon. The term strength as applied to cannon metal is not confined to tensile strength alone, but embraces also elasticity, ductility, and crystalline structure, which affect its power to resist the enormous and oft-repeated force of gunpowder. (See ORDNANCE, STRAINS UPON.) Each discharge of a cannon, however small, impairs its strength, and repeated a sufficient number of times, will burst it; this arises from the fact that the feeblest strains produce a permanent elongation or compression of iron; this is technically known as the permanent set, and the same is probably true of all other metals. The property of ductility is of importance in enabling a metal to resist rupture after it has passed its elastic limit. The size and arrangement of the crystals of a metal have an important influence in its strength to resist a particular force. A metal will be strongest when its crystals are small, and the principal faces parallel to the straining force, if it be one of extension, and perpendicular to it, if it be one of compression. The size of the crystals of a particular metal depends on the rate of cooling; the most rapid cooling giving the smallest crystals.

_Cast iron_ is very generally employed, notably in the United States, in the fabrication of heavy cannon for siege and sea-coast purposes. It possesses the very important qualities of tenacity, hardness, and cheapness, and with proper care is not seriously affected by rust. Its principal defect is an almost entire want of elasticity, in consequence of which its tenacity is destroyed after a certain number of applications of the straining force. But little is known of the causes which affect the quality of the cast iron used for cannon metal. The amount of carbon, the state of its combination, together with the ore, fuel, and fluxes, and the process of manufacture, all materially affect the quality of the iron. All that is known is, that certain ores treated in a certain way make cast iron suitable for cannon, and the fitness of a particular kind of cast iron for artillery purposes can only be determined by submitting it to the tests of the service. After this is known, a knowledge of certain physical properties, such as tenacity, hardness, density, and color, form and size of crystals presented in a freshly fractured surface, will be useful in keeping the metal up to the required standard. The pig-iron from which cannon are made should be soft, yielding easily to the file and chisel; the appearance of the fracture should be uniform, with a brilliant aspect, dark gray color, and medium-sized crystals. When remelted and cast into cannon, it should have about sufficient hardness to resist the file and chisel, but not to be so hard as to be bored and turned with much difficulty; its color should be a bright gray, crystals small, structure uniform, close, and compact. The density of gun metal should be about 7.25, and its tenacity about 30,000. There are several varieties of cast iron differing from each other by almost insensible shades. The principal divisions are, however, gray and white. Gray iron is softer and less brittle than the white, is slightly malleable and flexible, and does not resist the file. It has a brilliant fracture of a gray or bluish-gray color. This iron melts at a lower temperature than white iron and becomes more fluid, contracts less and contains fewer cavities; it fills the mold well, the edges of a casting are short, and the surface smooth, convex, and covered with carburet of iron. Gray iron is the only kind suitable for making castings which require great strength, such as cannon. White iron is very brittle, resists the file and chisel, and is susceptible of high polish, the surface of a casting is concave, the fracture presents a silvery appearance. Its qualities are the reverse of those of gray iron; it is therefore unsuitable for ordnance purposes. Mottled iron is a mixture of white and gray; it has a spotted appearance, and flows well. The casting has a plane surface with edges slightly rounded. It is suitable for making shot and shells. Besides these general divisions, there are several other varieties of iron whose qualities depend upon the proportion of carbon, and the state in which it is found in the metal. The color and texture of cast iron depend greatly on the size of the casting and the rapidity of cooling. See ORDNANCE, STRAINS UPON.

_Wrought iron_ was among the earliest metals employed in the construction of cannon, but in consequence of the defects which almost invariably accompany the forging of large masses, it was superseded by bronze and cast iron to a great extent. Wrought iron is softer than cast iron, and, being pure iron, is more liable to be corroded by the action of the atmosphere and products of combustion of the powder; it possesses also considerable ductility. The tensile strength of wrought iron, which under the most favorable circumstances is double that of the best cast iron, depends on the character of the crystalline structure, and the manner of applying the tensile force, or in other words, wrought iron offers the greatest resistance to a force of extension when the structure is fibrous, and the force acts in the direction of the fibres. The practical difficulties of rapidly cooling large masses so as to form small crystals, and compressing them by hammering, rolling, or otherwise to develop and give a particular direction to the fibre, have not thus far been wholly surmounted. On the contrary, large masses are generally found to contain such internal defects as false welds, cracks, and a spongy and irregularly crystalline structure, arising from the more rapid cooling of the exterior surface.

_Steel_ is a compound of iron and carbon, in which the proportion of the latter seldom exceeds 1.7 per cent. It may be distinguished from iron by its fine grain, its susceptibility of hardening by immersing it when hot in cold water, and with certainty by the action of diluted nitric acid, which leaves a black spot on steel, and on iron a spot which is lighter colored in proportion as the iron contains less carbon. For the construction of cannon, steel may be divided into high and low steel, the difference being that the former contains more carbon than the latter. High steel is very hard and has great ultimate tenacity. It has but little extensibility within or without the elastic limit, and is therefore too brittle for use in cannon, unless used in such large masses that the elastic limit will not be exceeded by the explosive force of the powder. It melts at a lower temperature than wrought iron and is difficult to weld, as its welding temperature is but little less than that at which it melts. Low steel is often known as “mild steel,” “soft steel,” “homogeneous metal,” and “homogeneous iron,” and is made by fusing wrought iron with carbon in a crucible; after which it is cast into an ingot and worked under a hammer. As it contains less carbon than high steel, it has greater specific gravity. It can be welded without difficulty, although overheating injures it. It more nearly resembles wrought iron in all its properties, although it has much greater hardness and ultimate tenacity, and a lower range of ductility depending on its proportion of carbon. It has less extensibility within the elastic limit than high steel, but greater beyond it, or in other words, greater ductility. Its great advantage over wrought iron for general purposes is that it can be melted at a practicable heat, and run into large masses possessing soundness and tenacity. Its advantages for cannon are greater elasticity, tenacity, and hardness. Its tenacity when suitable for cannon is three times as much as cast gun iron, and one-half more than the best wrought iron. The principal varieties of steel are:

_Natural Steel._--This is made principally in Germany, and is used for making files and other tools. It is obtained by reducing the rich and pure kinds of iron ore with charcoal, and re-fusing the cast iron so as to bring it to a malleable state. The India steel, or Wootz, is a natural steel containing a small proportion of other metals.

_Blistered Steel._--This is prepared by exposing alternate layers of bar-iron and charcoal in a close furnace for several days. When taken out the bars are brittle in quality and crystalline in appearance. The purpose for which the steel is to be used determines the degree of carbonization. The best qualities of iron (Russian and Swedish) are used for the finest kind of steel.

_Tilted Steel._--This is blistered steel moderately heated and subjected to the action of a tilt-hammer, by which means its density and tenacity are increased.

_Shear Steel._--A blistered or natural steel refined by piling thin bars into fagots, and then rolling or hammering them into bars, after they have been brought to a welding heat in a reverberatory furnace. The quality is improved by a repetition of this process, and the steel is known accordingly by the names, half shear, single shear, double shear, etc.

_Cast Steel._--This is made by breaking blistered steel into small pieces, and melting it in close crucibles from which it is poured into iron molds. The ingot is then reduced to a bar by hammering or rolling with great care. Cast steel is the finest kind of steel, and is best adapted for most purposes; it is known by a very fine, even, and close grain, and a silvery homogeneous fracture. The most remarkable specimen of cast steel for tenacity which is on record was manufactured at Pittsburgh, Pa. It was tested at the Washington Navy-Yard, and found to sustain 242,000 pounds to the square inch. The strength of cast steel usually runs from 70 to 140,000 pounds.

_Bessemer Steel._--This steel is produced by forcing air into melted iron, by means of which the carbon and silicon of the crude cast iron is oxidized. The essential difference between this process and the ordinary puddling is mechanical, and consists in the intense and violent stirring of the Bessemerized iron, to which alone is due the production and maintenance of a temperature, without any other fuel than the carbon and silicon contained, that keeps the metal fluid so that it can be cast into homogeneous malleable ingots. When decarburation has been carried far enough, the current of air is stopped, and a small quantity of white pig-iron containing a large amount of manganese is dropped into the liquid metal. No very large cannon have yet been made wholly of Bessemer steel, but several small ones have, which have shown great endurance. Experiments at the Woolwich Arsenal have shown that the tenacity of this steel is more than doubled by hammering.

_Siemens-Martin._--In this process the ingredients of cast steel are melted together on the open hearth of a reverberatory furnace of special construction, and a certain proportion of manganese necessary to make a sound and practically malleable steel added. This steel is, however, little used in gun construction.

_Semi-Steel._--If in the process of puddling or decarbonizing cast iron the process be stopped at a particular time, determined by indications given by the metal to an experienced eye, an iron is obtained of greater hardness and strength than ordinary iron, to which the name of semi-steel, or puddled steel, has been given. The principal difficulty in its manufacture is that of obtaining uniformity in the product, homogeneity and solidity throughout the entire mass. It is much improved by reheating and hammering under a heavy hammer; but it has not been found a reliable material for even cannon of small caliber. The celebrated guns made by Mr. Krupp of Germany are of cast steel, made from puddled steel, and of peculiar character, combining great tensile strength with the property of stretching to a great extent without breaking. Sir Joseph Whitworth improves the qualities of steel for his more recent guns by casting it under hydraulic pressure.

_Chrome Steel._--An alloy of iron and chromium, which is not steel in the ordinary sense, but which possesses many of its characteristics. The tensile strength and resistance to crushing is much higher than ordinary cast steel. This material has been largely used in bridge-building, but has not yet been applied to cannon-making.

_Bronze_ for cannon (commonly called brass) consists of 90 parts of copper and 10 of tin, allowing a variation of one part of tin more or less; by increasing the proportion of tin, bronze becomes harder, but more brittle and fusible; by diminishing it it becomes too soft for cannon, and at the same time loses a part of its elasticity. Bronze is more fusible than copper, much less so than tin. It is harder, less susceptible of oxidation, and much less ductile than either of its constituents. Its fracture is of a yellowish color, with little lustre, a coarse grain, irregular, and often exhibiting spots of tin which are of a whitish color. The density and tenacity of bronze when cast into the form of cannon, are found to depend upon the pressure and mode of cooling. In consequence of the difference of fusibility of tin and copper, the perfection of the alloy depends much on the nature of the furnace and the treatment of the melted metal. By these means alone the tenacity of bronze has been carried up to 60,000 pounds. Bronze is but slightly corroded by the action of the gases evolved from gunpowder, or by atmospheric causes; but its tin is liable to be melted away at the sharp corners by the great heat generated in rapid firing. It is soft, and therefore liable to serious injury by the bounding of the projectile in the bore. This injury is augmented as the force of the rebound is increased by the elasticity of the metal. It was established by experiments of Maj. Wade of the U. S. Ordnance Corps more than twenty years ago that the tensile strength of bronze is related to its density. It has been discovered since that this density can be produced by artificial compression. Two men claim the honors of the invention--Gen. Uchatius of the Austrian army, and S. B. Dean, an American inventor. The methods are essentially the same. After the gun is cast, steel mandrels slightly conical in shape are driven through the bore by hydraulic pressure,--each being succeeded by one slightly larger,--thus enlarging the bore and compressing the metal surrounding it. It is claimed that the bronze is thus rendered harder and stronger, and the defects above cited in a large measure obviated. The term “steel bronze” or “bronze steel” has been applied to the metal so treated. Many guns have been made of it for the Austrian service,--the largest of which is a 6-inch breech-loader throwing a projectile of 85 pounds. This gun has proved itself slightly superior in power to the same sized Krupp gun of steel.

_Aluminium Bronze._--An alloy of 90 parts of copper and 10 of aluminium. It is harder than ordinary bronze; much stronger, being 100,000 pounds to the square inch; it does not tarnish readily. Its properties would seem to especially fit it for a gun metal. _Phosphor bronze_ is an alloy with very similar properties.

_Combined Metals._--Numerous trials have been made to improve the strength of cannon by combining two or more metals in such a way that the good qualities of one will counteract the defects of the others. But the only metals used to any extent are those described above. Steel is constantly gaining in favor as a cannon metal. It is now almost exclusively employed throughout Europe, and wherever the Krupp gun is used. The great perfection arrived at by Krupp and others in the manufacture of steel seems to place that metal above all others for gun construction, whilst the difficulty of handling large masses has been overcome by the enormous power of the machinery used. Steel is also sparingly employed both in the United States and England for converting smooth-bore guns into rifles according to the Palliser method, but experiments in the United States have shown that it is inferior to wrought iron for this purpose. See ORDNANCE, CONSTRUCTION OF.

Wrought and cast iron are much used in this way for cannon in both the United States and in England. In the former, all the larger cannon belonging to the official system (both siege and sea-coast) are made of the cast metal, whereas the Parrott gun and the new rifled pieces are a combination of both. (See ORDNANCE, CONSTRUCTION OF.) The metal chiefly employed in England is wrought iron, in combination with steel; the largest guns made at the Woolwich Arsenal are of this nature. Bronze, except as modified by the Austrians, has now nearly entirely gone out of use as a cannon metal. In France and the United States, field-pieces, mortars, and howitzers are still made of this material.

=Ordnance, Strains Upon.= The exterior form of cannon is determined by the variable thickness of the metal which surrounds the bore at different points of its length. In general terms, the thickness is greatest at the seat of the charge, and least at or near the muzzle. This arrangement is made on account of the variable action of the powder and projectile along the bore, and the necessity of disposing the metal in the safest and most economical manner. The pressure at different points may be approximately determined by calculation, or, more accurately, by experiment. In the latter method, the plan generally employed consists in boring a series of small holes through the side of a gun at right angles to its axis at known distances apart. A steel ball is projected from each hole in succession into a target, or ballistic pendulum, by the force of the charge acting through it, and the pressure at the various points is deduced from the velocities communicated to these balls. This method was adopted by Col. Bomford. Instead of the projectile a steel punch may be employed, which is pressed by the force of the charge into a piece of soft copper. (See PRESSURE-GAUGE.) The weight necessary to make an equal indentation in the same piece is then ascertained by a testing machine. The strains to which all fire-arms are subjected may be classified as follows: (1) The tangential strain which tends to split the piece open longitudinally, and is similar in its action to the force which bursts the hoops of a barrel. (2) The longitudinal strain which acts to pull the piece apart in the direction of its length. Its action is greatest at or near the bottom of the bore, and least at the muzzle, where it is nothing; these two strains increase the volume of the metal to which they are applied. (3) A strain of compression which acts from the axis outward to crush the truncated wedges of which a unit of length of the piece may be supposed to consist; this strain compresses the metal and enlarges the bore. (4) A transverse strain which acts to break transversely by bending outward the staves of which the piece may be supposed to consist. This strain compresses the metal on the inner and extends it on the outer surface. It is known that rupture will take place due to the tangential strain alone, when three times the pressure upon a unit of surface of the bore is greater than twice the tensile strength. Due to the longitudinal strain alone, rupture will take place in the direction of the length, when the pressure is greater than twice the tensile strength; and if the transverse strain alone is considered, rupture will take place when twice the pressure is greater than three times the tensile strength. It therefore appears that the tendency to rupture is greater from the action of the tangential force than from any other, and for lengths above two, or perhaps three calibers, the tangential resistance may be said to act alone, as the aid derived from the transverse resistance will be but trifling for greater lengths of bore; but for lengths of bore less than two calibers, this resistance will be aided by both the transverse and the longitudinal resistance. Every piece should therefore have sufficient thickness of breech to prevent splitting through the latter; after this point has been attained, any additional thickness of breech adds nothing to the strength of the piece. It therefore appears that a fire-arm is strongest at or near the bottom of the bore, and that its strength is diminished rapidly as the length of the bore increases to a certain point (probably not more than three calibers from the bottom); after which, for equal thickness of metal, its strength becomes sensibly uniform. The metals of which cannon are made being crystalline in structure, the size and arrangement of the crystals have an important influence on its strength to resist a particular force; and a metal will have the greatest strength with reference to a particular force when its crystals are small, and the principal faces are parallel to the straining force, if it be one of extension, and perpendicular to it, if it be one of compression. The position of the principal crystalline faces of a cooling solid is found to be perpendicular to the cooling surface; the result of this arrangement of crystals is to create planes of weakness where the different systems of crystals intersect. The effect of this law upon cannons, it has been discovered, is to render radial specimens more tenacious than those cut tangentially from the same gun. The manner and rapidity of cooling have also a great effect upon the ability of cannon to resist strains, and as all solid bodies contract their size in the operation of cooling, it follows that if the different parts of a cannon cool unequally, it will change its form, provided it be not restrained by the presence of a superior force. If it be so restrained, the contractile force will diminish the adhesion of the parts by an amount which depends on the rate of cooling of the different parts, and the contractibility of the metal. This is an important consideration in estimating the strength and endurance of cannon, particularly those made of cast iron. All such cannon cooled from the exterior (see ORDNANCE, CONSTRUCTION OF) are affected by two straining forces; the outer portion of the metal being compressed, and the interior extended, in proportion to their distances from the neutral axis or line composed of particles which are neither extended nor compressed by the cooling process. The effect of this unequal contraction may be so great as to crack the interior metal of cast iron even before it has been subjected to the force of gunpowder. The strain produced by the explosion of gunpowder is not distributed equally over the thickness of metal, but it varies inversely as the square of the distance from the centre; it therefore follows that the sides of a cannon are not rent asunder as by a simple tensile force, but they are torn apart like a piece of cloth, commencing at the surface of the bore. Hence it is that the effect of ordinary cooling is to diminish the strength and hardness of the metal of cannon at or near a point where the greatest strength and hardness are required, _i.e._, at the surface of the bore. The strains produced by unequal cooling increase with the diameter of the casting and the irregularity of its form. This explains the great difficulty found in making large cast-iron cannon proportionally as strong as small ones, and also how projections like bands, moldings, etc., injure the strength of cannon. It also explains why cannon made of “light” cast iron, or cast iron made more tenacious by partial decarbonization, are not so strong as cannon made of weaker iron; for it is well known that such iron contracts more than the latter in cooling, and therefore produces a greater strain of extension on the surface of the bore. Capt. Rodman of the U. S. Ordnance Department has proposed a plan for cooling cannon from the interior (see ORDNANCE, CONSTRUCTION OF), thereby reversing the strains produced by external cooling, and making them contribute to the endurance rather than to the injury of the piece. It is likely, however, that the strains produced by unequal cooling are modified by time, which probably allows the particles to accommodate themselves to a certain extent to their constrained position. In confirmation of this, great endurance has been frequently found in _old_ solid cast guns, as in the old 42-pounders tested about the beginning of the war, 1861-65.

=Ordnance Department.= In the United States, was first established May 14, 1812, and was not provided for in the reduction of the army in 1815, but continued in the service. In 1821 the department was merged into the artillery, attaching to each regiment of artillery 1 supernumerary captain, and giving to each company 4 subaltern officers. The corps of ordnance was re-established April 5, 1832. The department consists of 1 brigadier-general, 3 colonels, 4 lieutenant-colonels, 10 majors, 20 captains, 16 first lieutenants, and 350 enlisted men. It is the duty of the senior officer of the ordnance department to direct the inspection and proving of all pieces of ordnance, shot, shells, small-arms, and equipments procured for the use of the armies of the United States; and to direct the construction of all cannon and carriages, and every implement and apparatus for ordnance, and all ammunition-wagons, traveling-forges, and artificers’ wagons; the inspection and proving of powder, and the preparation of all kinds of ammunition and ordnance stores. It is also the duty of the senior officer of the ordnance department to furnish estimates, and, under the direction of the Secretary of War, to make contracts and purchases for procuring the necessary supplies of arms, ordnance, and ordnance stores, etc. In the British service, the ordnance department was a distinct branch of the war department, originally for the supply of all warlike stores used in the naval or military service. The first master of ordnance was created in the time of Henry VIII., and the Tower of London was probably the depot of arms and military stores; Robert, earl of Essex, is said to have been the first master-general, in 1596. It does not appear that the ordnance department of the British service became especially military until the early part of the 18th century, after the organization of the Royal Artillery, in 1743, under the Duke of Montague as master-general. From this time the ordnance department was administered by a master-general and board, the latter being composed of a lieutenant-general of ordnance, surveyor-general, clerk of the ordnance, principal store-keeper, clerk of the deliveries, and treasurer. About 1763 the department became a construction board, with charge of all forts and fortresses, and directed the construction of all the fortifications and military store-houses, and barracks for the ordnance corps. The board was finally abolished as a separate department, the duties carried on by the commander-in-chief, and the various civil branches by separate offices under the secretary of state for war.

=Ordnance Office.= Before the invention of guns, this office was supplied by officers under the following names: the bowyer, the cross-bowyer, the galeater, or purveyor of helmets, the armorer, and the keeper of the tents. Henry VIII. placed under the management of a master-general, a lieutenant, surveyor, etc. The master-general was chosen from among the first generals in the service of the sovereign. The appointment was formerly for life; but since the restoration, was held _durante bene placito_, and not unfrequently by a cabinet minister. The letters patent for this office were revoked May 25, 1855, and its duties vested in the minister of war. The last master-general was Lord Fitzroy Somerset, afterwards Lord Raglan.

=Ordnance Projectile.= See PROJECTILE.

=Ordnance Sergeants.= In the U. S. service, are staff sergeants who are selected from the sergeants of the line of the army. Their duties consist in receiving and preserving the ordnance, arms, ammunition, and other ordnance stores at posts, under the direction of the commanding officer of the same. They must not be confounded with sergeants of ordnance, who are sergeants in the ordnance detachments at arsenals, etc.

=Ordnance Store-keeper.= In the British service, is a civil officer in the artillery who has charge of all the stores, for which he is accountable to the office of ordnance.

=Ordnance Store-keeper.= In the U. S. army, an officer of the ordnance department who holds the rank of captain. The grade has been abolished by act of Congress, and the duties appertaining to the office will be performed by other officers of the ordnance department.

=Ordnance Stores.= See ORDNANCE.

=Oregon.= One of the Pacific States of the American Confederacy. Oregon was the name formerly given to the whole territory north of the Rocky Mountains, and was first claimed by the Spanish government, and next by the government of the United States, as far as lat. 54° 40′ N. This latter claim was resisted by the British government, which asserted a right to the entire territory, and in 1818 a treaty was made, and renewed in 1827, giving joint occupation to the disputed territory. In 1846 a treaty was concluded, by which the boundary was settled on the 49th parallel. Previous to this latter treaty (1839) emigration from the United States, for the purpose of settlement, commenced, and it continued steadily until the opening of the gold mines in California, which attracted a great many emigrants. In 1849 it formed a Territorial government, and in 1859 it was admitted into the Union as a State. This State has been troubled greatly by Indians, and has been the scene of several wars in earlier days, notably, in 1853, on Rogue River; in 1855, when a general outbreak took place, of which the following is a brief summary: In 1855 a war broke out between the whites and the Indians of Washington Territory. The head and front of the outbreak on the part of the Indians was Kam-ai-a-kin. He took this stand from a fixed principle: that of resisting all encroachments on the part of the whites. He had seen the fate of the Indian race in the Willamette Valley, and he determined to anticipate such a result with regard to his own people, and, if possible, to prevent it. When Gov. Stevens made his arbitrary treaties with him, and left him no discretion but to sell his land; and when the miners began to traverse his country, he concluded that the hour had arrived to fight, and he called to his aid as many of the adjoining tribes as he could persuade into it. The manner in which the treaties on Puget Sound were conducted created great dissatisfaction among the Indians, and they were quite ready to join Kam-ai-a-kin. The war commenced by the killing of miners, who were picked off in the Yakama country as they were going to Fort Colville, scarcely a month after the council which was held at Walla Walla. The killing of the agent Bolen set the war in a blaze. The small detachment of troops sent to chastise them was driven back. This success on the part of the Klickatats encouraged the Sound Indians, who also took up arms, and in the absence of troops, fell upon and killed the inhabitants of White River; but the wholesale slaughter of women and children by a party under the command of Major Lupton on October 8, 1855, drove the Indians to desperation and caused them to commence the war in earnest; hostilities continued until the summer of 1856. Also, in later years, the Modoc war (1872), the Nez Pérces (1877), and the Bannock war (1878).

=Oreillere= (_Fr._). Oreillet, ear-piece of an ancient helmet, shaped like an oyster-shell, for protecting the ear and cheek.

=Oreillon= (_Fr._). Ear of a sword, languet, or small slip of metal on the hilt, which, when the sword is sheathed, extends along the scabbard.

=Organization.= The act of assigning and putting troops into such uniform state of discipline as may fit them to co-operate on any service. _Organization_ may be said to be begun by grouping those combatants who have the same mode of action. These groups are known as “arms of service.” An arm of service may be defined to be “a union of combatants having the same mode of action.” There are four of these arms in modern armies, viz.: _Infantry_, _Cavalry_, _Artillery_, and _Engineers_. These four arms form the principal part of a mobilized army, and as they or their representatives are always formed into a line of battle to resist the attack of an enemy, or to make an attack, they are generally known as the “line of the army” or “troops of the line,” to distinguish them from other bodies of men who form parts of an army. These _arms_ are subdivided into fractions for the purpose of instruction and of supply. The unit for instruction and the unit for supply may be the same or different. The unit of supply, as a general rule, is constant, and is also usually the unit of instruction in discipline. The unit of instruction in tactics will depend upon circumstances, and upon the kind of movements the commander desires to make. The common unit for the four arms, for supplying the men’s wants and for instruction in discipline, is the “company.” This unit receives, at other times, other names, depending upon circumstances. For instance, a _battery_ of artillery is the same as company; the term _squadron_ of cavalry frequently means a company, etc.

_A company_ consists of a given number of men commanded by a commissioned officer who has the rank of captain. Two, sometimes three, and even more commissioned officers of a grade below that of captain are appointed to assist the captain in the discharge of his duties. These officers have the grade of lieutenant. Their number and the number of men forming a company are fixed by law. A certain number are selected from the men and appointed non-commissioned officers, with the rank of sergeant or of corporal. These non-commissioned officers are used to instruct the men in their military duties and in discipline. The whole company should be divided into _squads_ of equal numbers, and each squad placed under the charge of a non-commissioned officer, who should be held responsible for the cleanliness of the men of his squad, not only as to their persons, clothing, and arms, but as to their tents or quarters. The _company_, with its size based on the theory that it must not be larger than one man on foot can thoroughly command in person, is the unit of organization. Two or three or more companies form a _battalion_. Four, and at the outside, five companies placed in line form, in these times, so extended a line that a single person in immediate and personal command of them will find difficulty in making himself heard and understood throughout the entire line. For this reason the battalion should not, as a rule, contain more than four companies.

_The battalion_ is the _tactical_ unit, both for instruction in tactics and in the execution of its movements. The battalion is sometimes made a unit of administration, and forms a complete organization under the command of a commissioned officer of the grade of major or lieutenant-colonel. The more usual rule is to increase the number of companies so as to have enough to form at least two battalions, and with these companies to form the organization known as a _regiment_.

_The regiment_ is always an _administrative_ unit, and is commanded by a commissioned officer who has the grade of _colonel_. The colonel is charged with the proper administration of the supplies for the regiment, and with preserving good order and promoting discipline. He takes every opportunity to instruct both the officers and men in the principles and details of all movements that ought in any case to be made by a battalion. Upon the organization of a regiment, the company officers are assigned to companies, and each company is designated by a letter of the alphabet. Upon the recommendation of the captains, the colonel appoints the non-commissioned officers of the companies. He appoints an adjutant from the lieutenants of the regiment, and a non-commissioned staff from the enlisted men, to assist him in his duties. He selects from the lieutenants a quartermaster, whose appointment is confirmed by the Secretary of War.

The elements of organization for the other three arms of service are practically the same, being that of a company or similar body of men under the command of a captain, and these units grouped together into a battalion or regimental organization for administrative purposes. This subdivision into companies and into regiments is most essential for instruction in discipline.

_Discipline_ is an indispensable condition for the existence of a good army. It imparts _cohesion_ and _flexibility_ to the armed mass. Without discipline an army is only an armed mob over which a commander would have no control, and upon which he could not rely in the execution of his plans. When the army is to be mobilized the regiments are brought together and organized into _brigades_ and _divisions_. Two or more regiments form a brigade; two or more brigades form a division. A general officer of the grade of _brigadier-general_ is assigned to the command of a brigade, and one of the grade of _major-general_ to the command of a division. These divisions and brigades may be composed entirely of one arm, or they may be composed of troops belonging to all four of the arms.

_The division_ is the unit of organization and administration of a mobilized army, and is also the _tactical_ unit of the general in command. When the army is very large, three or four divisions are joined together and form an _army corps_. The officer commanding an army corps should be of a higher grade than he who commands a division. This grade in the U. S. army would be that of _lieutenant-general_.

_An army corps_ is most generally composed of all arms of service, and is, to all intents and purposes, an army complete in itself. Two or more army corps or armies would be under the command of the _general_, or of a “general-in-chief.” There has arisen an organization forming an essential part of every army, known as the _general staff_, and divided into corps and departments to which are assigned special duties. In some cases, the term “general staff” is limited to include only those officers who are used by the general to communicate his orders, and to inform him of the general and particular conditions of the troops; and the term “staff department” or “supply department” is used to include those officers whose duties are confined to distinct branches of service having for their object the supply of troops. If the army is one of very great size, the general ordinarily attaches to his headquarters a representative of the three arms of artillery, cavalry, and engineers, giving them the position of staff-officers with the name of “chief of artillery,” “chief of cavalry,” etc. They are required to keep the general informed of the state of supplies, and whatever concerns their particular arm, in a similar manner to that required by the other officers of the staff. The general also appoints from the subordinate officers belonging to his command a certain number of _aides-de-camp_. These officers are _ex officio_ adjutants-general, and receive orders from the general himself. They are confidential officers, who are supposed to be used only in delicate and difficult duties, where they may in a degree represent the general. Hence, they are intrusted to deliver verbal orders which cannot be intrusted with propriety to enlisted men or to the ordinary means of communication.