After a severe competition it appeared that the best weapon would be produced by combining Henry’s system of rifling with Martini’s mechanism for breech-loading. The parts constituting the lock and the mechanism for working the breech, shown in Fig. 86, are contained in a metal case, to which is attached the woodwork of the stock, now constructed in two parts. To this case is attached the butt of the rifle by a strong metal bolt 6 in. in length, A, which is inserted through a hole in the heel-plate. The part that closes the breech—termed the “block”—is marked B. It turns loosely on a pin, C, passing through its rear end and fixed into the case at a level somewhat higher than the axis of the barrel. The end of the block is rounded off so as to form with the rear end of the case, D, which is hollowed out to receive it in a perfect knuckle joint. Let it be observed that this rounded surface, which is the width of the block, receives the whole force of the recoil, no strain being put on the pin, C, on which the block turns. In the experiments a leaden pin was substituted, and the action of the mechanism was not in the least impaired. This arrangement serves greatly to diminish the wear and the possibility of damage from the recoil. As the pin on which the block turns is slightly above the axis at the barrel, it follows that the block, when not supported, immediately drops down below the barrel. Behind the trigger-guard is a lever, E, working on a pin, F, fitted into the lower part of the case. To this lever is attached a much shorter piece called the “tumbler,” which projects into the case, G. It is this tumbler which acts as a support for the block, and raises it into its firing position or lowers it according as the lever, E, is drawn toward a firer or pushed forward. How this is accomplished will be readily understood by observing the form of the notch, H, in which the upper end of the tumbler moves. It will be noticed that the piece being in the position for firing, if the lever be pushed back, G slides away from the shallower part of the notch into the deeper, and the block accordingly falls into the position shown in the figure; and if again the lever is drawn backward, G acting on H will raise the block to its former position. The block or breech-piece is hollowed out on its upper surface, I, so as to permit the cartridge to be readily inserted into the exploding chamber, J. The centre of the block is bored out, and contains within the vital mechanism for exploding the cartridge, namely, a spiral spring, of which the little marks at K are the coils in section. These coils pass round apiece of metal called the “striker,” which is armed with a point, capable of passing through a hole in the front face of the block exactly behind the percussion-cap of the cartridge when the block is in the firing position. When the lever handle is moved forward, it causes the tumbler, which works on the same pin, to revolve, and one of its arms draws back the striker, compressing the spring in so doing, so that as the block drops down the point of the striker is drawn inwards. In this position the piece receives the cartridge into the chamber. The lever, E, being now drawn backward, the piece is forced into the notch, H, and the block is kept firmly in its place; besides this, there is a further compression of the spring by the tumbler, and in this position the spring is retained by the rest-piece, L, which is pushed into a bend in the tumbler. By pulling the trigger this piece is released, so that the tumbler can revolve freely, and relieve the pent-up spring, whose elasticity impels the striker forward, so that this enters the carriage directly. A very important and ingenious part of this arrangement is the contrivance for extracting the case of the exploded cartridge. The extractor turns on the pin, M, and has two arms pointing upwards, N, which are pressed by the rim of the cartridge pushed home into two grooves cut in the sides of the barrel. It has another arm, O, bent only slightly upwards and pointing towards the centre of the case, and forming an angle of about 80° with the above-mentioned upright arm; when, by pushing forward the lever, its short arm drops into the recess, the block, no longer supported, falls, and hits the point of the bent arm of extractor, so causing the two upright arms to extract the cartridge-case a little way.

The barrel is of steel; the calibre is 0·451 in. It is rifled on Mr. Henry’s patent system. The section of the bore may be generally described as a heptagon with re-entering angles at the junctions of the planes, so that there are fourteen points of contact for the bullet, viz., one in the middle of each plane, and one at each of the re-entering angles. The twist of rifling is one turn in 22 in. The charge consists of 85 grains of powder, and a bullet weighing 480 grains, of a form designed by Mr. Henry. The cartridge is of the same general construction as the “Boxer” cartridge, used in the Snider rifle, but it is bottle-shaped, the diameter being enlarged from a short distance in rear of the bullet, in order to admit of its being made shorter, and consequently stronger, than would be otherwise possible. A wad of bees’-wax is placed between the bullet and powder, by which the barrel is lubricated at each discharge. The sword-bayonet to be used with this rifle is of a pattern proposed by Lord Elcho. It is a short sword, broad towards the point, and furnished on a portion of the back with a double row of teeth, so as to form a stout saw. It is so balanced as to form a powerful chopping implement, so that, in addition to its primary use as a bayonet, it will be useful for cutting and sawing brushwood, small trees, &c.

The following are the principal particulars of weight, dimensions, &c., of the Martini-Henry rifle:

As an evidence of the accuracy of fire in this rifle, it may be stated that of twenty shots fired at 1,200 yards, the mean absolute deflection of the hits from the centre of the group was 2·28 ft. The highest point in the trajectory at 500 yards is rather over 8 ft. so that the bullet would not pass over a cavalry soldier’s head within that distance. The trajectory of the Snider at the same range rises to nearly 12 ft. The bullet will pass through from thirteen to seventeen ½ in. elm planks placed 1 in. apart at 20 yards distance; the number pierced by the Snider under similar circumstances being from seven to nine. As regards rapidity of fire, twenty rounds have been fired in 53 seconds; and one arm which had been exposed to rain and water artificially applied for seven days and nights, and had during that time fired 400 rounds, was then fired, without cleaning, twenty rounds in 1 minute 3 seconds.

Rifles of the Martini-Henry and Chassepot type were soon superseded, for as early as 1876 Switzerland had armed her troops with a magazine rifle of a smaller calibre than any then in use, and this weapon was found so effective that in a few years after every European nation had followed suit, as also had the United States and Japan, each country adopting some particular pattern of a weapon with certain modifications. Of these the Mannlicher and the Mauser are much used. A magazine rifle is one that can be fired several times successively without reloading. Like revolvers, the magazine arms repeat their fire, but instead of having several distinct firing chambers, they have but one, from which the empty cartridge cases are automatically extracted by the breech mechanism, for the magazine rifle is necessarily a breech-loader. The magazine rifle carries a supply of cartridges, which one after another are brought into the firing chamber by the simple action of the breech mechanism, so that the soldier is enabled to discharge several rounds in any position without reloading. The several varieties of the magazine rifle may be classed according to the position of the magazine. This may be: First, in the stock; second, under the barrel; third, in a box under the breech; or fourth, in a box above the breech. In the first and second variety the cartridges are in line in a tube, out of which they are moved on by a spiral spring, and this was the earlier form of the weapon. The box above or below the breech is the later development, and has the advantage of holding the cartridges lying side by side, and thus in a position in which they are not so liable to injure each other as in the tubular arrangements. Then, again, the movement of the cartridge in the breechbox in arriving at the firing chamber is much less than in the linear magazines, and the centre of gravity of the whole changes but little when the supply is exhausted. With any of the varieties of magazine a suitable modification of the mechanism may be adopted, so that the weapon can at will be used as a single firing rifle, but changeable in an instant to the magazine form. Again, the box magazine may be made as a fixture on the rifle, or it may be detachable. Commissions of military authorities had for several years been deliberating upon the best models for their respective nations, while Professor Hebler was working out his researches as to the best calibre for military rifles. Hebler published a work showing the great advantages of a bore one-third less in diameter than that commonly in use, which was about 0·45 inch, as in our Martini-Henry. The small-calibre rifle shoots straighter and hits harder than the large bore one, and the recoil is less, and so is the weight of the weapon. Lead is found to be too soft a material for the bullet of the small-bore rifles, as it does not keep in the rifling, which has a sharper turn than that in the older weapon; hence the bullets are now cased in steel or nickel. These bullets have remarkable power of penetration. Some will go through a steel plate 1¼ inch thick, making a clean hole in it, and the Lebel bullet penetrates 15 inches of solid oak, at a distance of 220 yards. Such a missile would, therefore, be capable of going completely through the bodies of several men or horses.

The Germans, about 1888, adopted a magazine rifle known as the Mauser. It had a fixed tubular magazine for eight rounds below the barrel, and a breech mechanism of the Remington-Keene type. The French followed suit with their famous Lebel gun, the construction of which was long kept secret. It also has a fixed under barrel tubular magazine, and the cartridges used with it contain smokeless powder. It is said that a new gun of practically the same pattern has been adopted by Russia, but with a detachable magazine to contain five rounds. The Russian gun will also use smokeless powder. In England, a small-bore rifle of 0·303 inches calibre is now issued to all troops. It has an under breechbox magazine, modified from the Lee rifle. The box is detachable, so that the weapon could normally be used as a single loader, and the magazine attached only when required. But the British authorities have decided that the magazine box is to be attached to the weapon by a chain. The first issue of this pattern of rifle to British soldiers took place early in 1890. The Austrians are adopting the Mannlicher pattern, in which the magazine idea is embodied in a complete and practical form. This rifle has a fixed box magazine below the breech. From this box, in which the cartridges—five in number—lie side by side, they are fed up by springs as they are disposed of by the movement of the breech mechanism. The magazine is recharged by placing in it a tin case containing five cartridges, and the case drops out when all the cartridges have been fired. In this form there is of course no necessity for providing any mechanism for holding the magazine in reserve while the rifle is used as a single loader. As to calibre, the Austrian authorities follow other countries in adopting a small bore, namely, 0·315 inch. Italy has converted her single-fire Vetterli rifle into a magazine arm, with a box something like the Mannlicher, and Belgium has adopted a gun of the same type. The rate of fire from charged magazines of such guns as the “Lee,” “Mannlicher” and “Vetterli,” worked with the right hand without bringing the piece down from the shoulder is, for all of them, about one shot per second; but the time that is required to recharge the magazines varies much according to the contrivance used. The number of rounds the magazine of a rifle is capable of containing when fully charged is from 5 to 12, or more, according to the difference of system. It is considered that in the detachable Lee or the quick recharging Mannlicher five rounds are ample for use at a critical moment.

The calibre of the military rifle has been decreased with almost every new pattern adopted. Thus, while the old “Brown Bess” had a calibre of 0·75 inch, in the last issue of it the bore was reduced to 0·693 inch; the Enfield (1852) had a bore of 0·577 inch; the Martini-Henry, 0·451 inch, which, in a newer pattern adopted in 1887, was reduced to 0·400 inch; and, finally, in the Lee-Metford, the calibre is only 0·303 inch. A similar consecutive reduction of bores has taken place in the rifles adopted by other countries, and one of the latest type, issued for the use of the United States Navy, has a bore of only 0·236 inch, and it is even expected that a still smaller one will become general. The advantage of the narrow and lighter projectile is that while it has a higher initial velocity with a given charge, its flight is less checked by the resistance of the atmosphere, the section it presents being so much less. Thus the bullet of 0·236 inch diameter has a section little more than one-fourth that of the 0·45 inch bullet. The difference is well shown in the comparative heights of the trajectory (or path of the bullet) of the Martini-Henry 0·450 inch bullet, and that of the 0·303 inch Lee-Metford (the latter with cordite ammunition); for at a range of 1,000 yards the former reaches to 48 feet above the line of sight, while the latter rises to only 25 feet.

Some form of repeating or magazine rifle has now been adopted by all the most important nations of the world. The number of shots contained in the magazines varies from 5 to 12. In the British detachable box magazine there are ten charges. The calibres of the barrels range in the infantry patterns of different nations from 0·256 inch to 0·315 inch; the explosive used in every case is some kind of smokeless powder, and this, in the cartridge for the Lee-Metford, is cordite. The bullets are not made simply of lead, but of lead coated with a harder metal or alloy such as steel, cupro-nickel, nickel steel, or they consist entirely of some of these alloys.

Although the magazine rifle is now the regulation weapon of the infantry of all great armies, it is not improbable that at no distant future it maybe superseded by one in which, as in certain machine guns, the force of the recoil will be used for actuating the breech and lock movements. Many patents have already been taken out for rifles on this principle, and several patterns have actually been constructed, in which a merely momentary contact of the breech-piece with the end of the barrel is sufficient; the recoil of the barrel with the reaction of a spring performs all the requisite movements with such rapidity that an amazing speed of firing has been obtained. It is said that such an automatic gun can send forth bullets at a perfectly amazing rate. Of course the mechanism of such a gun is somewhat intricate, and it is impossible to explain its construction and action without a great number of diagrams and much description.

RIFLED CANNON.

Having briefly sketched in the foregoing section the development of the military rifle from such weapons as our own “Brown Bess,” down to the repeating or magazine rifle, we now purpose to adopt a similar course with regard to ordnance, giving also some particulars of the methods of manufacture, etc., and following in general the order of history.

Naturally there is nothing that accelerates progress in warlike inventions so much as the exigences of war itself. This is well exemplified in circumstances attending the Crimean War, which was waged in 1854 by England and France in alliance against Russia. The desire of having ships that could run the gauntlet of the heavy guns mounted on Russian forts led to the construction of La Gloire and other armour-plated vessels, as we have already seen, and a suggestion of the French Emperor, as to improving metal for guns, made to Mr. Bessemer, led incidentally but ultimately to the great revolution in the manufacture of steel, although it is true that Krupp of Essen had begun to produce small cast-steel ordnance as early as 1847. But what determined the necessity for rifled ordnance was more particularly the greater comparative effects obtained by the muzzle-loading rifles over the field artillery then in use in the several engagements that took place in the Crimea, especially in the battle of Inkerman (1854). The rifles so much surpassed in accuracy at long ranges the smooth-bore field-pieces firing spherical projectiles, that field artillery was on the point of losing its relative importance, and even in the matter of range the latter lost so much by windage that the men serving the artillery could sometimes be leisurely picked off by the rifle sharp-shooters. Inventors were soon at work on devising methods of increasing the accuracy of ordnance fire with both light and heavy pieces, and before the end of the war some cast-iron guns rifled on Lancaster’s plan had been mounted on forts and in ships, without proving very successful except in regard to increase of range when elongated pointed projectiles were used with them.

Now let us see of what kind was the ordnance used for some years after the middle of the century, in order that we may be the better able to appreciate the progress that has since been made. Ordnance is, as already noticed, of several species, as guns mounted on fortresses, naval guns, siege guns, field-guns, etc., and the size of the pieces under each of those heads is distinguished sometimes in one, sometimes in another of three different ways. We may name it by the weight of the gun itself in tons or hundredweights, as “a 35–ton gun,” etc.; or by the weight of its projectile, as “a 68–pounder,” etc.; or by its calibre, that is the diameter of its bore, as “a 4–inch gun,” etc. We may take the naval guns with which Nelson won his battles (Trafalgar, 1807) as representative of all except field ordnance up to about 1856. They were all made of cast iron, threw spherical projectiles, and were very rudely mounted. The gun most commonly mounted on board our ships of war was the 32–pounder, weighing 32 cwt., shown with its carriage in Fig. 90. The carriage was of wood, and consisted of two side pieces joined back and front by two transverse pieces and carried by four low wooden wheels. The trunnions of the gun fitted into bearings at the top of the side-pieces, and were secured by iron plates that passed over them in a semi-cylindrical form and were bolted down to the wood. The position of the trunnions on the gun was always such that the breech end of the gun preponderated, being supported on an adjustable wooden wedge; and when the muzzle of the gun had to be lowered, this was done by raising the breech end with handspikes and pushing in the wedge so far as to prevent the breech from dropping down again. There was a vent or narrow passage to contain a train of powder from the touch-hole at the upper part of the breech to the rear of the charge. When the gun was fired, with its muzzle protruding a little way out of the port-hole, the recoil would trundle it inwards about its own length, when its course would be stayed by a thick rope attached to the sides of the vessel; and by other tackle it would be kept in position until loaded, when it would be allowed to roll back, or would be drawn by ropes and pulleys out to the port-hole, and by the same means such lateral inclination as might be required could be given. This last adjustment was called training the gun. A 32–pounder required the services altogether of a dozen or fourteen men, but these by virtue of constant drill would learn to handle the clumsy machine with a certain amount of expedition. If we except a notch on the highest point of the muzzle, the pieces were devoid of anything of the nature of sights, though sometimes marks were made on the adjustable wedge under the breech to correspond with certain elevations. Nor were sights required; for the mode of fighting then was to get quite close to the adversary’s ship and pour in a broadside by firing simultaneously all guns on the enemy’s side when they had been trained (by rough methods), so as to concentrate their effect as much as possible on one point of the antagonist. Nelson’s famous ship the Victory carried a few larger guns than the 32–pounders, namely, two 68–pounders, called carronades (from having first been cast at Carron in Scotland), and some 42–pounders. The 32– and 42–pounders numbered together thirty, and there were also as many 24–pounders, with forty 12–pounders. These were all simply cast of the required dimensions, and were not made with the one single improvement which after two centuries’ use of cast-iron guns had been introduced into France about fifty years before, namely, the boring of the chase out of a solid casting.

On the outbreak of the Crimean War (1854) the minds of many inventors were occupied by the problem of ordnance construction, and this also engaged the attention among others of two of the most eminent British mechanical engineers of the day. These were Sir W. Armstrong and Sir J. Whitworth, who, with others, were invited by our War Department to submit the best models of field and heavy guns their skill was severally able to produce. Two years afterward, Sir W. Armstrong had, after many experiments, completed a gun of 1·88 in. calibre. This had a forged steel barrel 6 feet in length; but it was only after eight such forgings had been bored and rejected on account of flaws revealed only by the boring that a sound barrel was at length obtained. This barrel was strengthened on the outside by jackets made from coils of wrought iron bars welded into a piece and shrunk on while hot (of which process we shall have something more to say presently); the barrel was rifled with many shallow grooves, and the pointed projectile, 3 calibres long, was made of lead, for which afterwards iron coated with lead was substituted. This gun was a breech-loader, the breech being closed by a block let into a slot after loading, and then pressed against the barrel by some turns of a screw which advanced parallel to the axis of the piece, and was made hollow for loading through, before the closing block was put in. In a trial of the various pieces ready in 1857, it was found that the Armstrong gun made as just described had an accuracy and range immensely greater than any weapon that had ever been tested, and the Government authorities approved of the system of construction, except that they preferred muzzle-loading pieces to breech-loading, as being simpler in action, more easily kept in repair, and cheaper in original cost and ammunition.

When Sir Joseph Whitworth’s gun was, in 1863, submitted to a competitive trial against the Armstrong, as to their endurance and mode of ultimate failure when fired with ever-increasing charges of powder and shot, at the forty-second round the Armstrong breech-loader split, and at the sixtieth the Armstrong muzzle-loader had one of its coils cracked; while it was not until the ninety-second round that the Whitworth gun burst violently into eleven pieces. These competing guns were 12–pounder field-guns weighing 8 cwts., and from each 2,800 regulation rounds had been fired before they were subjected to the bursting proofs. The result of these trials being that the authorities considered that steel was not then sufficiently reliable, and they decided to adopt the system of building up rifled guns with iron jackets over an inner tube of steel. Sir Joseph Whitworth made his guns entirely of steel, and they were striking examples of beautiful and accurate workmanship. His system of rifling consisted in forming the bore of the gun so that its section is a regular hexagon, and the projectile is an elongated bolt with sides exactly fitting the barrel of the gun: the projectile is, in fact, a twisted hexagonal prism. Fig. 91 shows at the left-hand side the section of the barrel, and on the right we see the form of the projectile on a smaller scale, this last representing, in fact, the exact size and shape of the bullet of the Whitworth rifle mentioned on another page. Sir Joseph’s guns were muzzle-loaders, and they were remarkable for their long range and accuracy of fire. One of these guns, with a charge of 50 lbs. of gunpowder, threw a 250–lb. shot a distance of nearly six miles, and on another occasion a 310–lb. shell was hurled through the air, and first touched the ground at a distance of more than six and a quarter miles from the gun. These distances are greater than any to which shot or shell had previously been thrown.

As the material of these Whitworth guns was very costly, and very perfect workmanship was required in the formation of the barrel and the shots, the expense attending their manufacture and use was much greater than that incurred in the case of the Armstrong guns. Sir W. Armstrong’s estimate for a 35–ton gun was £3,500, and Sir J. Whitworth’s, £6,000. The gun, as constructed at Woolwich on Mr. Fraser’s plan, was estimated to cost £2,500. The first cost of a gun is a matter for consideration, since each piece, even the strongest, is able only to fire a limited number of rounds before it becomes unsafe or useless. It appears that no cannon has yet been constructed capable of withstanding without alteration the tremendous shocks given by the explosion of the gunpowder, and these alterations, however small at any one discharge, are summed up and ultimately bring to an end what may be termed the “life of the piece.”

About the year 1858 Sir William Armstrong (afterwards Lord Armstrong) established at Elswick, Newcastle-on-Tyne, a manufactory of ordnance, which has since developed into the great arsenal now so well known all over the world. Here all the resources of science have been applied to the problems of artillery, and experiments carried on with a prodigality of cost and promptness of execution impossible at a government establishment trammelled with official regulations. Here, and also at Woolwich, our national ordnance factory, guns have since always been constructed on the building-up plan advocated by Sir W. Armstrong, whose principle consists in disposing of the fibre of the iron so as best to resist the strains in the several parts of the gun. Wrought iron being fibrous in its texture has, like wood, much more strength in the direction of the grain than across it. The direction of the fibre in a bar of wrought iron is parallel to its length, and in that direction the iron is nearly twice as strong as it is transversely. A gun may give way either by the bursting of the barrel or by the blowing out of the breech. The force which tends to produce the first effect acts transversely to the axis of the gun; hence the best way to resist it is to wrap the iron round the barrel, so that the fibres of the metal encircle it like the hoops of a cask. The force which tends to blow out the breech is best resisted by disposing the fibres of the iron so as to be parallel to the axis of the gun; hence Sir W. Armstrong makes the breech-piece from a solid forging with the fibre in the required direction. But the Elswick building-up principle involves much more than the direction of the fibres of the iron, for each coil or jacket, after having its spires welded together, was bored out on a lathe, and the exterior of the part of the gun on which it was to be placed was also turned with the utmost exactness, so that when the enveloping piece was heated to a certain temperature and in this state brought into position, it would in cooling compress the parts it encircled just to that degree which careful calculations showed would best strengthen the gun without unduly straining the metal at any part. The Elswick guns being built up of several superimposed jackets of calculated lengths and thicknesses, the means was afforded of distributing the tensions throughout the whole mass of metal to the best advantage. In the simpler form, arranged by Mr. Fraser, and for the sake of economy adopted by the authorities at Woolwich in 1867, the greater part of the benefit derivable from adjustment of tension was no doubt sacrificed to cheapness of manufacture. These, and also the forms of Armstrong guns that have not yet been described, ceased to be made after 1880, by which time steel had replaced iron in every part of the construction and fittings of guns, and muzzle-loading had been definitely abandoned in favour of breech-loading.

Now, in 1874, when the first edition of the present work was in preparation, the Fraser-Woolwich guns were in full vogue, being spoken of by the public press as the ne plus ultra of artillery construction in size, efficiency, and economy. When, accordingly, the author had been privileged to visit the arsenal and witness the production of these guns in every stage of their manufacture, he wrote a description of it which is here retained as printed at the time, seeing that it may not be without historical interest, particularly since great numbers of these guns must still be extant, mounted on our forts in various parts of the world, and seeing also that the description of the simpler formations may render more easily to be understood future references to similar operations in gun-making as have been retained in the later developments. Of course, the following description was written in the present tense, and therefore in perusing it the reader must constantly bear in mind that the guns with which our ships of war have since been equipped are in every respect entirely different from

The Fraser-Woolwich Guns, 1867–1880.

Until the year 1867 the guns made at Woolwich were constructed according to the original plan proposed by Sir W. Armstrong, and on this system one of the large guns consisted of as many as thirteen separate pieces. These guns, though unexceptionable as to strength and efficiency, were necessarily so very costly that it became a question whether anything could be done to lessen the expense by a simpler mode of construction or by greater economy in the material. The problem was solved in the most satisfactory manner by Mr. Fraser, of the Royal Gun Factory, who proposed an important modification of the original plan, and the adoption of a kind of iron cheaper than had been previously employed, yet perfectly suited for the purpose. Mr. Fraser’s modification consisted in building up the guns from only a few coils, instead of several, the coils being longer than Sir W. Armstrong’s, and the iron coiled upon itself two or even three times: a plan which enabled him to supersede the breech-piece, formerly made in one large forging, by a piece formed of coils. In order to perceive the increased simplicity of construction introduced by Mr. Fraser, we need but glance at the section of a 9 in. gun constructed according to his system, Fig. 94, and remember that a piece of the same size made after the original plan had ten distinct parts, whereas the Fraser is seen to have but four. Compare also Figs. 92 and 93. We shall now describe the process of making the Fraser 9 in. gun. The parts of the gun as shown in the section, Fig. 94, are: 1, the steel barrel; 2, the B tube; 3, the breech-coil; 4, the cascable screw. The inner steel barrel is made from a solid cylinder of steel, which is supplied by Messrs. Firth, of Sheffield. This steel is forged from a cast block, the casting being necessary in order to obtain a uniform mass, while the subsequent forging imparts to it greater solidity and elasticity. After the cylinder has been examined, and the suitable character of the steel tested by trials with portions cut from it, the block is roughly turned and bored, and is then ready for the toughening process. This consists in heating the tube several hours to a certain temperature in an upright furnace, and then suddenly plunging it into oil, in which it is allowed to remain for a day. By this treatment the tenacity of the metal is marvellously increased. A bar of the steel 1 in. square previous to this process, if subjected to a pull equal to the weight of 13 tons, begins to stretch and will not again recover its original form when the tension is removed, and when a force of 31 tons is applied it breaks. But the forces required to affect the toughened steel in a similar manner are 31 tons and 50 tons respectively. The process, unfortunately, is not without some disadvantages, for the barrel is liable to become slightly distorted and even superficially cracked. Such cracks are removed by again turning and boring; the hardness the steel acquires by the toughening process being shown by the fact that in the first boring 8¼ in. diameter of solid steel is cut out in 56 hours, yet for this slight boring, in which merely a thin layer is peeled off, 25 hours are required; and lest there should be any fissures in the metal, which, though not visible to the eye, might make the barrel unsound, it is filled with water, which is subjected to a pressure of 8,000 lbs. per square inch. If under this enormous pressure no water is forced outwards, the barrel is considered safe. It is now ready to have the B tube shrunk on it.

The B tube, like certain other portions of these guns, is constructed from coiled iron bars, and this constitutes one great peculiarity of Sir W. Armstrong’s system. It has the immense advantage of disposing the metal so that its fibres encircle the piece, thus applying the strength of the iron in the most effective way. The bars from which the coils are prepared are made from “scrap” iron, such as old nails, horse-shoes, &c. A pile of such fragments, built up on a wooden framework, is placed in a furnace and intensely heated. When withdrawn the scraps have by semi-fusion become coherent, and under the steam hammer are soon welded into a compact mass of wrought iron, roughly shaped as a square prism. The glowing mass is now introduced into the rolling-mill, and in a few minutes it is rolled out, as if it were so much dough, into a long bar of iron. In order to form this into a coil it is placed in a very long furnace, where it can be heated its entire length. When sufficiently heated, one end of the bar is seized and attached to an iron core of the required diameter, and the core being made to revolve by a steam engine, the bar is drawn out of the furnace, winding round the core in a close spiral, so that the turns are in contact. The coil is again intensely heated, and in this condition a few strokes of the steam hammer in the direction of its axis suffice to combine the spires of the coil into one mass, thus forming a hollow cylinder.

The B tube for the 9 in. gun is formed of two double coils. When the two portions have been completely welded together under the steam hammer, the tube, after cooling, is roughly turned and bored. It is again fine bored to the required diameter, and a register of the diameter every few inches down the bore is made. These measurements are taken for the purpose of adapting most accurately the dimensions of the steel barrel to the bore of the B tube, as it is found that perfect exactness is more easily obtained in turning than in boring. The steel barrel is therefore again turned to a size slightly larger than the bore of the B tube, and is then placed muzzle end upwards, and so arranged that a stream of water, to keep it cool, shall pass into it and out again at the muzzle, by means of a syphon, while the B tube, which has been heated until it is sufficiently expanded, is passed over it and gradually cooled.

If now the B tube were allowed to cool spontaneously, its ends would, by cooling more rapidly than the central part, contract upon the steel barrel and grip it firmly at points which the subsequent cooling would tend to draw nearer together longitudinally, and thus the barrel would be subjected to injurious strains. In order to prevent this, the B tube is made to cool progressively from the breech end, by means of jets of water made to fall upon it, and gradually raised towards the muzzle end, which has in the meanwhile been prevented from shrinking by having circles of gas-flames playing upon it.

The breech-coil, or jacket, is formed of three pieces welded together. First, there is a triple coil made of bars 4 in. square, the middle one being coiled in the reverse direction to the other two. After having been intensely heated in a furnace for ten hours, a few blows on its end from a powerful steam hammer welds its coils perpendicularly, and when a solid core has been introduced, and the mass has been well hammered on the sides, it becomes a compact cylinder of wrought iron, with the fibres all running round it. When cold it is placed in the lathe, and the muzzle end is turned down, leaving a shoulder to receive the trunnion-ring. The C coil is double, welded in a similar manner to the B coil, and it has a portion turned off, so that it may be enclosed by the trunnion-ring.

The trunnion-ring is made by punching a hole in a slab of heated iron first by a small conical mandrel, and then enlarging by repeating the process with larger and larger mandrels. The iron is heated for each operation, and the trunnions are at the same time hammered on and roughly shaped—or, rather, only one has to be hammered on—for a portion of the bar which serves to hold the mass forms the other. The trunnion-ring is then bored out, and after having been heated to redness, is dropped on to the triple breech-coil which is placed muzzle end up, and the turned end of the C coil (of course, not heated) is then immediately placed within the upper part of the trunnion-ring. The latter in cooling contracts so forcibly as to bind the ends of the coils together, and the whole can thus be placed in a furnace and heated to a high temperature, so that when removed and put under the steam hammer, its parts are readily wielded into one mass. The breech-coil in this state weighs about 16 tons; but so much metal is removed by the subsequent turnings and borings, that it is reduced to nearly half that weight in the gun. It is then turned in a lathe of the most massive construction, which weighs more than 100 tons. Fig. 34, page 95, is from a drawing taken at Woolwich, and shows one of the large guns in the lathe. No one who witnesses this operation can fail to be struck with the apparent ease with which this powerful tool removes thick flakes of metal as if it were so much cheese. The projections of the trunnions prevent the part in which they are situated from being finished in this lathe, and the gun has to be placed in another machine, where the superfluous metal of the trunnion-ring is pared off by a tool moving parallel to the axis of the piece. Another machine accomplishes the turning of the trunnions, the “jacket” being made to revolve about their axis. The jacket is then accurately bored out with an enlargement or socket to receive the end of the B tube, and a hollow screw is cut at the breech end for the cascable.

The portion of the gun, consisting of the steel barrel with the B tube shrunk on it, having been placed upright with the muzzle downwards, the breech-piece, strongly heated, is brought over it by a travelling crane, and slips over the steel barrel, while the recess in it receives the end of the B tube. Cold water is forced up into the inside of the barrel in order to keep it cool. As the breech cools, which it is allowed to do spontaneously, it contracts and grips the barrel and B tube with great force. The cascable requires to be very carefully fitted. It is this piece which plays so important a part in resisting the force tending to blow out the end of the barrel. The cascable is a solid screw formed of the very best iron, and its inner end is wrought by scraping and filing, so that when screwed in there may be perfect contact between its face and the end of the steel barrel. A small annular space is left at the circumference of the inner end, communicating through a small opening with the outside. The object of this is, that in case of rupture of the steel barrel, the gases escaping through it may give timely warning of the state of the piece.

Besides minor operations, there remain the important processes of finishing the boring, and of rifling. The boring is effected in two operations, and after that the interior is gauged in every part, and “lapping” is resorted to where required, in order to obtain the perfect form. Lapping consists in wearing down the steel by friction against fine emery powder and oil, spread on a leaden surface. The piece is then ready for rifling. The machinery by which the rifling is performed cannot be surpassed for its admirable ingenuity and simplicity.

In this operation the gun is fixed horizontally, its axis coinciding with that of the bar, which carries the grooving tools. This bar is capable of two independent movements, one backwards and forwards in a straight line in the direction of the length of the bar, and the other a rotation round its axis. The former is communicated by a screw parallel to the bar, and working in a nut attached to the end of it. For the rotatory movement the bar carries a pinion, which is engaged by a rack placed horizontally and perpendicularly to the bar, and partaking of its backward and forward movement, but arranged so that its end must move along another bar placed at an angle with the former. It is this angle which determines the pitch of the rifling, and by substituting a curved guide-bar for the straight one, an increasing twist may be obtained in the grooves.

The projectile used with these guns is of a cylindrical form, but pointed at the head, and the moulds in which these shots are cast are so arranged that the head of the shot is moulded in iron, while the body is surrounded with sand. The rapid cooling induced by the contact of the cold metal causes the head of the shot to solidify very quickly, so that the carbon in the iron is not separated as in ordinary casting. In consequence of this treatment, the head of the shot possesses the hardness of steel, and is therefore well adapted for penetrating iron plates or other structures. The projectiles are turned in a lathe to the exact size, and then shallow circular cavities are bored in them, and into these cavities brass studs, which are simply short cylinders of a diameter slightly larger than the cavities, are forced by pressure. The projecting studs are then turned so as accurately to fit the spiral grooves of the guns. Thus the projectile in traversing the bore of the piece is forced to make a revolution, or part of a revolution, about its axis, and the rapid rotation thus imparted has the effect of keeping the axis of the missile always parallel to its original direction. Thus vastly increased accuracy of firing is obtained.