Ar the last Exhibition, enclosed in a select paling, was a series of the famous guns of the two cannoniers Armstrong and Whitworth. Exquisite toys they seemed, rather than fatal instruments-so delicate, so exquisitely worked, so smooth and shining, so gently bulbous, so rich and lusciously brown. No wonder that the French artilleryman exclaimed, in a sort of professional rapture, that there was here "un luxe et une puissance d'outillage merveilleux." They had, indeed, all the perfection and nicety of surgical instruments, and were made with the marvellous accuracy of an astronomical quadrant. Nor was this surprising, when the skilful Whitworth had actually among his tools a little machine that could indicate an alteration of a millionth part of an inch; and was training his workmen, in their cannon practice, to deal easily with such quantities as the twenty thousandth part of an inch. These are, indeed, the delicacies of war, and such charming playthings are almost the jewellery and trinkets of the profession. Yet the whole-instruments, workmanship, science, skill, startling ranges, everything-may be said to have come into being since the Crimean war. Before that date, scientific gentlemen conducting experiments with the "Bess" of the soldier, on a windy day had to aim, say four hundred yards, to the right or left. It may be said that there is about as much difference between the weapon-cannon or musket-of ten years back, and the guns turned out of the Whitworth and Elswick foundries, as between the same weapon and the old arquebus of some hundred years back.

It is said that the amendment is owing to the substitution of civilians for military in the supervision of the manufacture a most satisfactory explanation. Could the principles be extended to other branches-say to courts martial, which are pretty much in the state they were, when the persons tried were firing arquebuses, it might have the same excellent results. The secret of these improvements consists really in giving its full de

velopment to the enormous force that lies dormant in a charge of gunpowder, and making the aim as certain as that of a light fowling-piece. The first object was secured by fresh strength of the cannon, and by a peculiar shape of the barrel and the missile (for ball it can be no longer called); and the second by rifling. The additional strength was the main problem; for the perfection of a gun was not merely to bear almost any charge without bursting, but to continue to bear it without bursting-for they are treacherous creatures, and, under certain conditions, are subject to a steady decay and weakness. The vulgar idea of mere thickness of iron has now been dispelled; and very happily, this is not the condition of strength, for the additional weight and bulk would more than counterbalance the advantage. Professors Barlow and Treadwell-one from the English Cambridge, the other from the American Harvard-have proved mathematically, that in cast iron, after a certain thickness, no more strength is secured by additional thickness. In other words, the outer layers become superfluous, from, perhaps, the force of the shock not reaching to them. Of what material, then, should a good gun be made?

The easiest and simplest plan-the oldest, too, and the cheapest—was to get a sand mould, with a core, and pour in melted iron. Here was a cast gun. The popular idea is that all iron is pretty much the same; but cast iron enjoys a very indifferent reputation for steadiness. When poured into the mould the outer surface is found to cool before the inner; it is contracted, and the inner surface cools later. The whole is wrenched, as it were, by this unequal process; and the surface has often been found quite porous

full of little cracks and flaws-and the intermediate region quite soft to the touch. It is obvious such offered but an indifferent security against bursting. The next idea would be that of forged iron--iron pounded and beaten into a firm, close texture, by the agency of hammers, as is done with a ship's anchor. This process

gives, it will be seen, an artificial density, and compactness, and must necessarily remove all pores and flaws. Still it was impossible, even by this method, to secure a proper texture in the metal. There was no guarantee against a solitary flaw escaping notice; and a solitary flaw internally would do all the mischief; for it is found that the powder gases act on such, even the slightest, like a wedge in a cleft, and every new discharge widens it steadily. Most rules have exceptions, and the gigantic exception in this instance is the monstrous Horsefall gun, which by reason of its enormous size is supposed to have endured, in spite of a crack fourteen inches long. But this was only a scratch upon the skin of a giant.

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There are further dangers, too, in iron guns, which have been cast or pounded into shape. There is the certain danger of what is called a set," which results from the conflict of the inner and outer surfaces of the gun. The inner surface has to bear a greater strain, while the outer, as the shock travels to it through a dense medium, suffers comparatively little. Very often, then, the inner surface is strained beyond even its power of elasticity, and does not return to its original state; whereas the outer, which has received merely the proper shock, and is returning to its normal state, is checked by the sudden interior enlargement. The result is a set," or general dislocation, the whole texture of the metal is shaken and disorganized, and the gun is sure to burst on the first opportunity. Reflecting on this state of things one of the most useful and thoroughly practical projects in connexion with this subject occurred to Captain Palliser. Turning over this theory of setting, and thinking, too, of the enormous number of stray cast iron guns which are in store, and lying scattered about the kingdom like stones in a field, and perhaps, too, thinking of certain ratepayers whose moneys are lavished a little profusely in the purchase of these articles, it occurred to him that this tremendous' accumulation of waste material might be turned to some profit. A gun has its youth, its manhood, and its old age. It is only allowed to live through a certain number of discharges, for it VOL. LXIII.NO. CCCLXXVII.

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is then known to become dangerous to its friends, and is forthwith cast out, as some Indian tribes do their old men. The accumulation is, therefore, in a tremendous ratio. Captain Palliser, therefore, without wishing to stand in the way of new inventions, takes thought only for those ancient veterans. He waits until the time of old age sets in, when either. the "set" or the flaw has declared itself. He then asks that the condémned gun may be handed over to him.

He knows that the strain on the outer lamina is very trifling as compared with that on the inner, and that therefore the outer surface of the gun and the metal underneath for a good way down is still sound. But the dislocated inner surface he cuts out altogether, flaws, "sets," and alland fits in a tube or series of tubes of wrought iron. By this process and by the fact of the outer tubes of the series being "shrunk" on the inner, the shock is made to travel through the whole mass with something like uniformity.

Cast and wrought iron being thus unsuitable-the former from its defects, the latter from the difficulty of using it in large masses, a new shape of the material, known as "homogeneous," was thought of, for which Krupp, of Berlin, an eminent founder, has attained a prodigious reputation. It consists of small ingots of the finest iron, picked as it were; these are melted into ingots which again are forged into masses. The strength and tenacity of this sort of artificial iron is amazing, and recommended it to Mr. Whitworth for his guns. So unyielding is it, that he has actually plugged the barrel of a "homogeneous" musket, and discharged it many times without bursting it. This valuable material, though the best hitherto discovered, is yet far from perfect; and it is owned by the great gun engineers that in large masses it is more or less uncertain and requires to be assisted by some artificial stays in the shape of rings or coils or tubes, which brings us to the two great rival guns of the day, Mr. Whitworth and Sir William Armstrong, whose merits Sir James Emerson Tennent has set out in a clear, simple, though scarcely impartial story, from which has been glean

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ed some of the facts in this paper. Sir William Armstrong deals with yet another shape of iron. He noticed that the welding together what might be called "strings of iron, produced a singular tenacity, and having in his mind the old "twisted barrel" of the common musket, conceived this pattern of a gun known now as the "Armstrong". a tube of steel which is not so much for strength as for a lining, which is wrapped round with a number of "welded coils." No better idea could be given of a welded coil than a flattened corkscrew-that is, the coils of which are flattened so closely as to transform it into a tube. A number of these are joined end to end, according to the length of the gun required. It will be seen that by this means the bursting strain is made to bear against the spirals of the corkscrew, as it were, and it has to struggle against a number of parallel bars; whereas in the common cast-iron gun there is nothing but a surface which is the same in every direction, either in the length of the gun or in its breadth.

The exquisite perfection to which Mr. Whitworth had brought his tools and machinery, served him in good stead for his principle. The interior bore is of equal width from end to end, but the outer surface tapers a little towards the muzzle, in the degree of about an inch in every hundred inches. The surface is then brought to a mathematical smoothness, and over it is drawn a sort of short stocking, tapering in exactly the same degree, which, by hydraulic pressure, is forced on up to the breech. This is considered preferable to putting it on hot, and then "shrinking" it on; and the surfaces correspond so accurately that the cohesion is perfect. These metal stockings are in short lengths, and joined on end to end. Over them again is drawn a second series, and over that again, at the breech, a third. The whole has then a tight compact mass, without any violent contraction or wrench of the metal from sudden cooling.

It is the misfortune of the Armstrong gun that, as an invention, all its notable features should be contested by many claimants. The "welded coil" has been claimed both by the American Treadwell and the Irish Captain Blakely. What the

Blakely gun is shall now be shown. These engines have received large patronage in foreign countries, but in truth there is little to distinguish their principle from that of Treadwell.

It was constructed of an inner tube of cast iron or steel, enclosed in a case of wrought iron or steel, heated or shrunk upon the inner cylinder. The diameter of the outer cylinder is made smaller than the inner, so as to compress it very tightly, and thus all portions take their share of the shock. Strange to say, the Ordnance Committee of 1861, with an inconceivable blindness, reported that the Blakely and Armstrong guns were the same in principle. But Captain Blakely does not admit the similarity, which is more obvious, between his and Treadwell's patent. But the truth is, this principle of "hooping" guns to give an artificial strength, is found to be an old plan, and is too simple a method of mechanical appliance (suggested every day by the common barrel or tub) not to have been thought of long ago. It is said to have been submitted to the French government so far back as 1833, and the Belgians made some experiments shortly after under the direction of Colonel Frederick. Mr. Mallet, with the same principle before him, brought out his 50-ton monster mortar; and Mr. Longridge constructed arms about the same time on the same principle, using wire ropes instead of hoops. But the principle is faulty: the shock is found, as might be imagined, to "start" the hoops. The strengthening power is not almost homogeneous with the mass it strengthens, as in the Whitworth cannon. Thus much for the material of the gun-in itself a doubtful matter to decide on, but in which some glimmering of light begins to guide us. Twenty years ago, when we had got thus far, the gun was virtually complete, a bore or touchhole being all that was needed; but now on this bore and the appliances depends the whole power of the gun. The mere brute-strength of the cannon is but a negative virtue-a mere basis, as it were. A hundred points arise:-should the barrel be broad or narrow, short or long, the same width all along, or smaller at one end than the other; should it be smooth or rifled, and if rifled, how should it be rifled? The Whitworth gun is

an open tube of equal width from end to end. The Armstrong tapers slightly to the muzzle for an object that will be seen later. The rifled Armstrong must be loaded at the breech, for this reason; the Whitworth may.

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Sir Emerson Tennent remarks, that this fancy of breech-loading has always exercised something like a fascination on inventors; there is a cloud of ingenious patents dealing with it; and yet, the advantage gained-except with the object of compressing the shot, as in the Armstrong gun-is very slight, not enough to compensate for the delicacy and consequent derangement of the mechanism necessary. In the Armstrong gun the shot or bolt is put in at the open breech, a 'vent-piece" is then dropped down, like the slide of a photographic camera, and a turn of a hollow screw, through which the ball had passed, fixes the slide tightly in its place. But there are grave objections to this system-the most common of all, that of the vent-piece being liable to be blown out. The cause of this is the imperfect contact of the breech screw and the ventpiece; and safety will be secured if the artillerymen are careful to see that the allowance should be exactly Tooths" of an inch! If the allowance is less or more, the soldiers, in the heat of rapid firing, become inaccurate in their calculation of the respective 1000ths. There is sure to be an accident; and as the ventpiece is kept firm by a hollow screw only, the pressure is merely caused by the edge of a ring and is unequal. The superior simplicity of the Whitworth plans commends itself at

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once.

Mr. Whitworth does not fancy the breech-loading system at all; but there is a craze for it; and he gratifies it with certainly the simplest form. The breech of his cannon swings back on a hinge, like the top of a heavy glass ink-bottle. The shot is put in, the cap shut back, and, with a turn or two, screws on tightly. There are no delicate pieces and fine adjustments, and but two pieces. Above all, the gun can be used as a muzzle loader. On the other hand, the touchhole of the rival gun, being in the movable vent-piece, can be renewed as often as necessary; for it

is well known that this is the most perishable feature in any gun.

The feats of the French " canons rayés" at Solferino and Magenta were what first attracted the public attention to the developing of a secret power in guns hitherto not utilized; and yet the idea was not new; it can be traced back a hundred years at least. The first English attempt in this direction was the Sebastopol Lancaster gun, with an oval or elliptical bore, with a slight twist, something in the nature of a turn in a hollow screw. But the gun has been unsuccessful, owing, it is believed, to the ball getting "jammed" in the gun.

But the utility of rifling once conceded, a hundred questions arose as to detail. Should the turns of the screw be rapid and numerous, or the reverse? The discussion fluctuated between as many turns as are in a corkscrew and a single wavy line-a fraction of a single turn, and so faint as to be scarcely appreciable. With numerous turns, there was an obvious loss of power, and a more violent strain on the gun. The tendency has, therefore, been to a turn, as nearly as possible in a line with the direction of the projectile. Sir W. Armstrong has carried out this principle so far, that he does not, strictly speaking, rifle," but merely grooves" his pieces; and the section of one of his guns seems like the outline of a circular saw. But there is a sacrifice of the spiral motion, which imparts an accurate aim to the shot.

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Mr. Whitworth scores, as it were, with a free hand the interior of his gun. Common rifling does not alter the character of the bore; but the Whitworth plan converts the interior of the gun into a sort of hollow screw. There is said to be a greater strain and violence on the gun where the shot first starts from, owing to the suddenness of the shock; and to obviate this, Captain Palliser ingeniously proposes that the ball should have travelled some part of its road before coming in contact with the rifling.

Having now the material, the shape, the bore, and the rifling-in short, all the appliances for despatching the missiles, and despatching it truly, the