Weight of Land and Sea Service Mortar.

The proportions of all guns to shot, will be found below; and in looking at this table, it will scarce be conceivable how such light guns can project such heavy shot.

Comparative Weights of Guns and Shot.

The recoil, which in all the before-mentioned guns is very great, arises from the blow communicated to the iron in immediate contact with the explosive fluid. The granulatory system of the metal transmits to those grains, or crystals, immediately behind them, the blow or concussion they are subjected to, and these again to others, and so on, until the vibration has passed through the metal, from the interior of the breech to the exterior of the gun.

I am satisfied that in all small guns, from their slight substance, recoil is communicated a great deal quicker than in larger ones; hence arises the well-known fact that in shooting you receive a knock nearly simultaneous with the explosion. The greater and heavier the gun (even carry it up to General Miller’s gun of 84 cwt.) if the proportion which the shot bears to it be not too great, the less will be the velocity of recoil. But in carronades, as will be seen, the proportions are as high as 1 to 55, while in long guns, it is 1 to 429; a very considerable degree of difference.

Our ancestors had but a limited knowledge of the laws of projecting bodies by gunpowder. Their explosive power was not good; for there is clear proof, even since the time of Robins, that the purification of the ingredients has nearly doubled the explosive force. The mechanical construction and outer mould of their guns, were calculated to resist and limit the effects of recoil to a great extent.

Accumulation of metal in the rear of the breech-end of a gun is true science, and of so easy an attainment, that wonder arises in the mind why it has not been effected. The extent to which this principle is worked upon in our gunnery is very trifling; though recoil can by this simple arrangement be nearly destroyed, or so lessened as to add considerable percentage of range to the projectile. Add no considerable weight to the gun, but add it judiciously, behind the end of the chamber and vent, and immediately surrounding the breech. I have tried this to a great extent, on a small scale, “with fowling-piece barrels,” and find that the greatest advantage arises from an additional inch of metal to the extreme end of the barrel, as the recoil is thereby lessened; while, on the contrary, by reducing the exterior end of the breech, until it becomes of less thickness than the sides of the barrel, the recoil is doubled. Guns will some day be constructed as mortars are, with the axles, or trunnions, in rear of the tube and of the vent; for by this arrangement recoil would act less on the mass of metal forming the gun, and more on the base from which it is fired. We are quite aware that an arrangement of this nature could only be applied to certain descriptions of ordnance, and in certain situations; but on forts, or batteries commanding rivers and bays, and even in the bows of steam vessels, they may be placed with great advantage. But this objection may be started: “You could not use guns fitted in this manner horizontally, or nearly so.” Why not? The muzzle could be as easily raised or depressed as the breech, by mechanical means. I should much like to see the principle tried, and I hope to do so.

The following results of experiments prove, that if a true basis is not laid down, all the fabric raised upon it is but one of sand, which will crumble away from under us. Hutton says,—“Varying the weight of the gun, produced no change in the velocity of the ball. The guns were suspended in the same manner as the pendulous blocks, and additional weights were attached to the pieces, so as to restrain the recoil; but although the arcs of the recoil were thus shortened, yet the velocity of the ball was not altered by it. The recoil was then entirely prevented, but the initial velocity of the ball remained the same.” No doubt this was the result of his experiments by the pendulous suspension of the gun: but here he erred; for had he suspended a thousand tons to it, without incorporating it in the gun, the result would still have been the same. All the improvements effected, or yet to be accomplished, will be obtained by a concentration of metal.

An excess of weight in the fore part of a gun is very injurious, by inducing and lengthening the tremulous vibration created by the explosion. The only necessity for strength forward in a cannon, arises from the necessity of resisting the lateral pressure from the condensation of the column of air in the tube. The pressure of the explosive gases is, by the velocity obtained before reaching the fore part, of very little amount, from the short period it is exerted on the interior. Therefore weight, in the fore part of a gun, be it ever so great, will not prevent recoil if there is not a proportionate quantity behind. It will retard or lessen the distance to which the recoil will drive the gun and carriage, but the evil is then over.

If the slightest movement occurs in the gun, the shot is projected from an unsound base or foundation. It is precisely similar to a man who, in the act of throwing a stone, slips his foot backwards: the effect is at once apparent on the stone. If the trunnion of a gun breaks in the discharge, or a quoin flies out, the shot is materially affected; never ranging, under such circumstances, the accustomed distance, nor with its usual accuracy. Practice with mortars proves beyond dispute the necessity of a firm base for the gun, for with a much less charge they project a greater mass farther. A mortar discharged on land, exceeds in range the same description of gun on board of ship, or on the best-constructed platform. In truth, this is but another illustration of a law of nature: if you have not a solid fulcrum, it matters little what the power of your lever may be. Gunpowder is a powerful lever if exploded on a solid base; if not, its effects become limited in proportion. Unquestionably, much may yet be gained by an economical arrangement of our projectile force. Great and rapid as have been the acquisitions of knowledge in everything relating to gunnery in modern times, there still remains, I have no doubt, an unexplored mine of valuable treasure to be added to the science.

It would effect a great improvement in the mortars used by the navy, destroying the tremendous vibration and shake given to the ship, increasing their efficiency and aiding the projecting power, to place them on beds of the softest lead, not less than twelve inches in thickness. Though this suggestion is only theoretical, experience would soon determine the least degree of substance available. Advantage would arise, in the first place, from the non-conducting tendency of the lead; in the second, from its density, and, of course, incompressibility. The one protecting the ship, the other being the most solid bed for the mortar that can by possibility be obtained.

The weight of a hollow 13-inch shell is 190 lbs.; the bursting powder 6 lbs. 8 oz.; the weight, if cast solid, would be 290 lbs.: thus the action of so large a body on the atmosphere must be immense of itself. There seems to be much difficulty in projecting masses of great diameter, from this cause; and this should lead us to seek, as indeed it points to, another material for fabricating projectiles. As weight is less in substance, and, of course, less in space, much less resistance, in proportion, will exist in a bore of six inches than in one of twelve; and a greater projectile force will be generated with fewer countervailing disadvantages.

The first step in the vast improvements about to be effected in gunnery, has been successfully taken by Mr. Monk, of Woolwich arsenal, who has induced the authorities to allow a gun to be made from drawings and calculations of his own. The dimensions of the gun are as follows: length from cascable to muzzle, 11 feet; weight, 97 cwt. 3 qrs.; bore, 7⁷⁄₁₀ inches; weight of solid shot, 55 lbs.; shell, 42 lbs.; windage, 0·175; charge, 16 lbs. of powder; giving a range, at 32° of elevation, of 5,327 yards. A compound shot, (a shell filled with lead), was projected 5,720 yards, or three miles and a quarter, at a velocity, during the first second of time, of 2,400 feet per second, and occupying during the whole flight only 29¹⁄₂ seconds. The comparative weight of gun and shot is 1 to 220.

A course of experiments, extending over seventeen years, has firmly established this gun as the best ever yet constructed. Many attempts have been made to excel it, but all have failed. Guns have been made on drawings varying not more than three-tenths of an inch in their dimensions from those of his gun, and, with extreme modesty, the individuals have claimed a right to compete with Mr. Monk; and have even obtained competing trials, without any claim whatever to the discovery of the principle of it; coming into competition by no just claim or merit, but solely from the tendency to supersede any improvement emanating from a civilian. Eighteen, twenty-four, and thirty-two pounders are now, however, constructed on this model;—indeed the improvement is so great and so apparent, as to overcome every obstacle as yet thrown in its way.

With no wish to detract from the merit of Mr. Monk’s invention (upon which I congratulate him and the country) but, in justice to myself, I may remind some of my readers, that in “The Gun,” published early in 1835, I clearly laid down the principle in projectile force, on which this gun is constructed; and as he has since so successfully accomplished this great improvement, he must permit me to say, that the principle is the same which I have striven for, for many years.

Wilkinson says, “Guns cast on this principle, although several hundredweight lighter altogether, recoil less than those on the old plan, with equal charges of powder and ball, in consequence of the weight being properly distributed.” He adds, “One remarkable fact attended these experiments, namely, that by increasing the windage a little, the range was increased also, contrary to the received opinion; but this may be explained by the circumstance, that with very great velocities, and long guns, the column of air to be displaced before the ball quits the gun is considerable, and is condensed so rapidly, that it offers immense resistance to the passage of the bullet, if it fit the bore closely; but, by reducing the size of the ball, and thus increasing the windage, the air has more space to rush round it, and the ball escapes with greater facility.”

If the condensed air prevented the velocity being greater, it argues most clearly, that there was an insufficiency of explosive matter to keep up the velocity until the ball of less windage left the muzzle; and the result with the ball of greater windage establishes this assumption. For if the condensed air was allowed to pass the ball by the windage into the tube, it proves beyond doubt that there was a deficiency of matter there, or that the pressure without was greater than that within. How otherwise could such a result occur? It is a clearly established fact, that with the generality of ordnance, a full waste of one-fourth of explosive force, if not more, occurs by the elastic fluid escaping past the ball by the windage, instead of the reverse. Neither could the condensed air rush into the gun by the windage if there are any permanent gases generated; which Mr. Wilkinson himself says there are, to the extent of “250 times the bulk of the powder in grain.” These would offer a sufficient resistance to prevent the condensed air rushing in. I have found, by an experiment before described, that a ball driven against a column of air which has no escape, if the velocity be trifling, say 800 feet per second, the air will escape by the windage; but double this even, and it is so condensed as to form a cushion for the ball to strike against. Then how much less will the chance be of its escaping, if the velocity become two thousand four hundred feet per second. No, the cause is remote from that of Mr. Wilkinson’s supposition. There is a want of force—an accelerative propellant force—which should continue to the end of the tube, be that length ever so great; and on this point, for one, turns the whole future improvement of gunnery.

The result wished for can be obtained by a systematical arrangement of the granulation of powder. That a much greater velocity than is obtained in this gun—at present the greatest in any piece of ordnance in use, and possessing a longer range than has been obtained by any power in Europe—may and will be attained, I fearlessly assert. I have obtained a velocity with an ounce ball nearly doubling this; and though, as it will be argued, this may be too limited an experiment, yet let us not forget that great results most frequently spring from little causes. Large rivers owe their origin to small springs, and if the same principle by which we can penetrate a plate of iron half an inch thick with an ounce of lead, be fearlessly and judiciously carried through, we may (and no doubt we shall) live to see projectiles thrown 5¹⁄₄ miles. That this will be difficult to accomplish I deny: no difficulty attends it, provided the principles before explained are duly carried out.

The great principle in a propellant force is so to arrange it that you do not obtain too great a velocity at the first move of the projectile; as no mass can be forced from a state of rest to a rapid state of motion, without communicating to the gun a corresponding motion, which will create a recoil: and the greater the motion, the greater the recoil. If the explosive matter merely expands for a brief period, and is burnt out before the shot has reached midway the length of the gun, the velocity there acquired will be reduced, by the condensed column of air in the other half of the barrel, to the velocity it possessed when only one fourth the length of the whole from the breech; consequently it would be advantageous to cut the gun in two at the middle, as a greater force would be then generated advantageously, than by the whole. But if you so arrange the granulation of your powder that it shall proceed into motion more gradually, a rapidly increasing force of elastic fluid will continue to be generated, until it reaches its greatest maximum of velocity (which it should do just as the ball leaves the muzzle) then you obtain with your means the greatest result possible.

We believe that the generality of gunpowder used by our Government is vastly inferior in strength to some made by private makers; yet it is not advisable to jump from one extreme to another. What is wanted is the proper blending of the qualities; an addition of a quantity of Harvey’s quick powder to a charge, when it has driven the ball up three-fourths of the tube of a gun, and probably had acquired a velocity of 2,000 feet per second, might so aid it, that it would leave the muzzle with a velocity of 3,000.

You cannot put a locomotive train in motion at once: if it were attempted, you would break all the carriages; but if you gradually add your force, you gain in time the greatest possible velocity. I have drawn a parallel case: it is the same with gunpowder; only the velocities are widely different. Therefore, I may be pardoned, if I say gunnery is like steam, but in its infancy. Let us but clearly see and understand aright the principle—knowing that the greater momentum the less the action of the atmosphere—and if 3¹⁄₄ miles can be obtained with a ball 60 lbs. weight, 5¹⁄₄ may be easily accomplished by a ball of 120 lbs. Powder is made, and can be had, that will do this.

The use of compound-shot has of late years become quite common in experiments: why lead, with its alloys, has not been more extensively used as a projectile for large guns, has always appeared to me extraordinary. Its weight and density peculiarly fit it for this purpose, and its non-conducting principle is its greatest recommendation. How is it? In no instance, except as compound-shot, do we find any record of the use of leaden bullets on a large scale, save in Sir Howard Douglas’s “Naval Gunnery,” where, in a note, he says, “A very distinguished naval commander mentioned to me, that he knew a person who had served in an American privateer, which, being out of shot, and unable to procure a supply of iron balls, used leaden shot as substitutes. This person always mentioned with great surprise the superior effect of leaden balls.” Well he might; for the reader need not be told that its greater specific gravity would add to its momentum, and a longer medium velocity be retained during its flight. But it possesses another recommendation, superior to all these, in warfare: that of communicating all its force, all its velocity, be they ever so great, to the body struck. Iron does not possess this quality; except to a certain extent, and that at low velocities. Hence the cause of its being found in naval warfare, that balls at low velocities damage and destroy ships’ sides more than at higher velocities, even when passing quite through. Lead, in the act of striking hard substances, iron or stone for instance, is partially flattened, until the flat surface is nearly equal to the diameter of the sphere of the ball; thus parting with all the force it struck the object with, and in most instances falling motionless at the base of the object struck; while in the stone, the surrounding crystals or grains are, by their abrasion on each other, pounded into dust, in proportion to the size and force of the body of lead striking them: in many instances to many times the shot’s bulk, and only flattening the lead, less or more, in proportion to the capability of the stone to resist. Iron striking stone retains its shape: the grains are driven back upon each other, and each offering its proportion of elasticity, the ball is enabled to rebound back; which it does in many instances to a considerable percentage of the whole distance it had been projected. The greater the velocity with which an iron ball is projected the greater the rebound back from a hard substance such as stone. Reversely, the greater the velocity of lead, the greater its effect on the object struck. Walls or fortifications struck by leaden balls at the same velocities (waiving the advantage to lead by its greater specific gravity) would be pounded into sand by less than two-thirds the same number of lead as of iron shot. Any unprejudiced person may soon satisfy himself of this, by trying it with a musket or fowling piece. A leaden ball will pound itself a hole many times its own bulk, while an iron ball will not make a hole half its size.

I have tried many experiments to ascertain the penetrating powers of iron and lead relatively, by striking various objects, from a boiler plate of half an inch thickness down to fir deals. The same size of lead will, under certain circumstances, punch a perfect hole in a plate of half-inch thickness, as I shall have occasion to show; while, under precisely the same arrangement, the iron ball would rebound back with very little diminution of force; and if the plate of iron be at a perfect right angle, the iron ball would nearly return into the muzzle, of the gun. In truth, I had a narrow escape seventeen years ago, from a bullet actually cutting the rim of my hat: so that it will be well, when experimenting in this way, to be sure that the person is well esconced, for fear of unpleasant results.

Lead, therefore, for destroying ships, as well as stone walls, is unquestionably highly advantageous; even if projected with the same velocities as at present adopted for iron. The additional weight would not decrease the destructive effects; it would augment them. I perfectly agree with the American privateer, that the wonderfully destructive power of leaden cannon balls will create surprise, whenever they shall come generally into use. Imagine the effect from a gun of the dimensions of a 10-inch bore. It is dreadful to contemplate.

The effect of lead will be easily understood when explained in the following way. If a 36 lb. shot have a velocity of 2,000 feet per second, the force is equal to the velocity multiplied by the weight, or 72,000 lbs. The whole of this force would strike a wall, and be left there, if communicated by soft lead; if by iron, at the same velocity, it would be minus the amount of force required to make it rebound to the great distance to which iron invariably returns. Though created by the elasticity of the iron itself, this must be deducted from the effect produced, and hence arises the great advantage the lead possesses. We are aware that iron driven with a slight velocity rebounds less; true, and less is its real effect; for under the very same circumstances would the great advantages of the lead predominate. It may be objected, that lead is too easily misshaped; “pure it is, but with alloys not so.” At low velocities it might, but the greater velocities diminish that chance, as it is a well known fact that all dense incompressible bodies are least affected by an extremely sharp motion. All our arrangements in warlike preparations, at present, involve great weight of projectile for fracturing, not perforating. During the siege of Ciudad Rodrigo, 2,159 rounds, of twenty-four and eighteen pounders, were requisite to form the small breach of thirty feet wide, and 6,478 rounds for the larger of 100 feet. At Badajos there was expended, to form three breaches of 40, 90, and 150 feet respectively, the enormous amount of 31,861 rounds of the same sized iron shot. We may be pardoned if we presume to say, one-half the number of lead shot would have done more, and done it better.

If we bear in mind, that the whole round of experiments from which Hutton drew his deductions, were conducted with iron projectiles, the inconsistency of taking his data as the standard will be apparent. The dissimilitude of specific gravities being great, namely, 7,425 and 11,327—or one-third difference—it clearly shows, without any effort of the imagination, that the range must be in the same proportion, with the addition of greater momentum. For it will scarcely be denied, that a ball of gold or platina, from the same cause, will maintain a velocity longer, and consequently range further, than even lead. Hutton’s theory only establishes the principle, that the lighter the body projected, the sooner it is acted upon by atmospheric resistance, and a medium velocity induced. We cannot attribute his preferring iron to arise from an opinion of its penetrating to greater depths; for a man of his extensive knowledge and research could scarcely be guilty of such an error. But even in our enlightened times we are told that elephants cannot be killed with any projectile but steel: leaden balls cannot do it. I should like to try, and receive the tusks in return.

The shrapnell shell (invented by General Shrapnell), or spherical case shot, introduced into the British service of late years, is probably the most destructive of any missile in use. It was intended to supersede—which it has done—canister and grape shot; effecting the same results at treble the range. The construction and principle are very simple, being merely a shell of an unusually light description; in fact, little more than a light cast-iron hollow ball, with a fuse hole. A certain quantity of leaden, or iron bullets is put into it, and the interstices around the ball shaken full of powder; a fuse of the length required is inserted, and explodes the shell during its flight: the peculiarity being, that the body of small balls retain their medium velocity and travel on, merely diverging, latterly, like an immense charge of bird shot. They are usually fired from howitzers, carronades, and other wide bored-guns, at or near horizontal ranges. A considerable delay occurred before they were successfully perfected. It was found that when the small balls did not pack perfectly tight, or were packed overtight, the case frequently exploded in the gun: occasioned, no doubt, by the friction creating a spark at the moment of the howitzer being fired, and thus exploding the shell before its time; but we believe such an occurrence rarely happens now, from other improvements since adopted.

The preceding pages appeared in my last work published in 1846. They are still so much in keeping with the state of gunnery at the present day, and so prophetic of what has, and is about to occur, that they will be regarded, I trust, as bearing the stamp of authority.

Progress, in its rapid advance, has made many English guns objects for the furnace or the museum; and many guns, which formerly ranked high as useful and important weapons, have become things of the past.

Monsters are now all the rage, with a range of three miles, and artillerists contemplate extending the range to double that distance; whilst the projectiles used are not “pounders,” but approximating to tons. So much for improvement. In political economy we are told that improvement to be good must be gradual; but only effect some slight improvement in gunnery, make but one step in advance, and the desire for further improvement then ranges at will, and impossibilities are craved for and sought to be attained.

Twelve years ago the success of Mr. Monck (certainly the first modern improver of ordnance,) led to the unlimited production of undigested plans for changes in gunnery; but, unfortunately for the science, no progress was made on the one great improvement of Mr. Monck.

War found us ill prepared in the field, and out-weighted “afloat,” so that almost as many men were killed by the bursting of mortars, and other ill-constructed guns, as by the fire of the enemy: so critical was our situation, indeed, that but for the general adoption in England’s army of my great invention, the rifle on the expansive or “Greenerian” principle, and its skilful use by our brave soldiers, the war had gone against us. Our rifles were equal in range to our artillery, and this saved us; whilst the enemy, astonished at the effects produced by our bullets, and conscious of their inferiority both in the construction and use of small arms, abandoned the contest: but no doubt with a firm determination to profit by their dear-bought experience.

It is generally admitted that our artillery was never so effective as that of the enemy, and that more is due to the patient and enduring bravery of the British soldier than to our field-pieces and heavy ordnance. That England’s artillery was at this time most disgracefully inefficient, it would be folly to deny. The larger guns were destroyed in an inconceivably short space of time. After five, ten, or fifteen rounds were fired the guns burst, killing the gunners in great numbers.

The readers of my works are already familiar with my opinions on this subject, and their value will now be enhanced by the fact that they have been proved to be the opinions of a “practical man.” Success in the improvement of small arms is a sure encouragement to those anxious for the advancement of projectile science, and it is a coat of mail in which to fight against the prejudices and incompetency of official management.

Who, on reading my work of 1841, believed the prediction I therein made, that small arms would be produced which would render field guns useless? The fact is, however, firmly established, that the best rifles on my principle will out-range by several hundred yards the best “six-pounder” in her Majesty’s service; and that, too, with a repetition of fire wonderfully quick and effective: as the Russians in the Crimea can testify, on more than one occasion.

To endeavour to point out that an improvement may be effected in artillery equal to that which has been effected in small arms, is the object of the following pages.

The author asks a dispassionate perusal and careful study of his work, in justice to himself and to the importance of the subject. Judging of future probabilities by what has already been accomplished, the reader will be prepared for what follows. That great and important changes must take place in artillery cannot be doubted, and should England refuse to avail herself of the improvements to be effected, other nations, and amongst them our late opponent, will be the first to seize and adopt them. In former works I have asked the indulgence of my military readers on account of my scanty military knowledge; but professional men appear to be equally in the dark with the uninitiated: indeed, the lamentable shortcomings of the English artillerists have placed them in the rank of mere “waiters upon providence” for the next step towards improvement. The present time is decidedly propitious; let improvements now be made, and we may surely hope that they will be appreciated by the public, if not by the Government authorities.

What is the best metal for cannon? is a question which has often been asked, and the answers have been very conflicting. Some have advocated mixtures of copper and tin; others have advocated cast iron, and more recently wrought iron; still more recently steel, and, lastly, cast steel, have had their advocates. Arguments as plentiful as summer flowers have been advanced in favour of each, and the argument has been carried on with a vast amount of prejudice and warmth, according to the degree of acquaintance with or attachment to the favourite metal of each individual. It is rare to meet with a mind free from bias, equally well acquainted with the merits of the several metals, and their application to the purposes intended. Still more rare is it to meet with a mind possessing all this metallurgic knowledge, and combining with it an intimate acquaintance with the principles of projectiles, as well as a scientific knowledge of the construction of the engine (the perfection of which consists in its having no points which are weak or unnecessarily strong); and yet it is by such a combination of knowledge and the application of these principles that we must be guided, if we would be successful in the accumulation of projectile power. In the present age we are really alive to the advantage of “playing at long bowls;” and the question now to be determined is, what is the greatest weight of shot and shell we can throw, and how many miles can we project it. The Americans were undoubtedly the first to discover the great advantage of this question with their lesser frigates; the late war has developed it still more; and it now remains to be ascertained how much further can we go. For on this important point the superior efficacy of artillery depends.

At St. Sebastian, in 1813, cast-iron guns threw tons of shot at a range of 1,500 yards; some particular guns firing as many as 3,000 rounds, and yet it is more than probable that had the same guns been used in the Crimea, they would have burst with one-fourth the number of rounds. Experience proves that it is not the great number of rounds fired which strains and destroys the gun, but the high elevation at which these guns are placed, in order to get range; this it is which shakes and disintegrates the crystalline structure of the metal, and thus extreme range is obtained at extreme cost. A gun which at 6° of elevation could stand without a strain 200 rounds, would be likely at an elevation of 30° to burst before 50 rounds were fired. The explanation of this is sufficiently simple. A gun fired at 6° recoils as the projectile is projected forward, in proportion to its relative weight and friction; but when brought up to an elevation above 30° the gun is entirely out of the horizontal, and cannot recoil as it does at an elevation of 6°: the force is now exerted downward, and the gun impinges on its support—i. e., either upon its bed on the deck of the ship, or on the solid earth of the battery, which is comparatively immovable; thus the force which displaced the gun in the first instance is now exerted on the sides of the gun, and the projectile receiving additional force is projected further. But this increased range is obtained at the expense of the gun, which is rapidly destroyed: 50 rounds being sufficient to render it unfit for service. To obviate this rapid destruction of cannon, the metal has been changed from the molecular to the fibrous; that is from cast iron to wrought iron. One object of this chapter is to point out the difficulties which arise in determining what the best metal for cannon really is, and to show the advantages to be gained by attending to the proper construction of projectile engines, without attaching undue importance to the material of which they are made.

Before rejecting cast iron as useless for the construction of large guns, it would be well to assure ourselves that no better quality of metal can be produced than that which is at present manufactured. We must also satisfy ourselves that we have clearly understood the proper shape and form of cannon to resist concussions. These concussions, be it remembered, were more violent in the late than in any previous war; and it is an undoubted fact that we had many more fractures then than on any previous occasion: first, on account of the strain produced by the great elevation required to get increased range; and, secondly, on account of the imperfect shape of the gun. The average number of rounds fired from the 13-inch mortars which burst at the bombardment of Sweaborg was 120, and the fracture in all was peculiarly alike; being at right angles to the supports. Now, that this is due to the form of the gun cannot be doubted; and it will be shown more fully in a subsequent page.

But there is another cause to which I wish now to direct attention, viz., the jamming of the Lancaster shell, which takes place in the increasing spiral of the oval gun at the very point where the projectile acquires a proportional increase of velocity. The effect of this may be illustrated by running a locomotive at its maximum of speed over an increasing curve in the railroad, with the certainty of landing it in an adjoining ditch. The principle which determines the result is quite immutable: viz., that matter in rapid motion cannot be materially affected by any force inferior to the primary force: the tendency of the body being to go straight forward; whereas a slow train goes round a curve with the greatest ease. Two motions can easily be given to matter in a lower velocity; but not so easily when the velocity is much increased. Hence I fear that the inventor of the Lancaster gun must have had a misconception of the true laws of motion; for by increasing the degree of spiral at the muzzle, instead of at the breech of the gun, he has rendered nearly useless what would otherwise have proved a most formidable engine of war.

From these observations it may, I think, fairly be doubted whether the bursting of cannon is owing entirely to the inferior quality of the cast iron used in their formation; though there can, I think, be no doubt that English cast iron is not only much inferior to what it formerly was, but that it is also inferior to that which is now manufactured in Russia. Why it is so will be subsequently explained.

These defects in cast iron have naturally led to many attempts to substitute for it a more durable metal; and in most cases the metal selected has been wrought iron. Wrought iron has been used, not only in solid cannon, but in the original “hoop and stave:” “staves outside,” and “staves inside,” as in Mr. Mallet’s monster mortar. Forms of gun as numerous as can be conceived have been constructed, only to prove themselves in every case most complete failures. Our friends at the Mersey Works, Liverpool, will, no doubt, demur to this assertion; as “all creations of the mind appear most perfect to the father of the thought.”

Great credit is, however, due to the enterprise and energy displayed by the inventors, forgers, and finishers of this great gun; which has been the wonder of many minds in this age of wonders: and it is a highly important invention, as showing what we, as a people, are capable of producing by our mechanical and engineering skill. But here, in my estimation, the wonder ceases; for so sure as there is any truth in the Scotch proverb, “A silk purse cannot be made out of a sow’s lug,” so surely is it true that no man, however great his genius and working powers, can make a good cannon of wrought iron. When the hardness and ductility of silver can be imparted to and held by lead, then will it be possible to make wrought iron accomplish all the purposes required of a good cannon.

In vain may Mr. Horsfall urge that his gun has never been burst. Why? Simply because it has not yet been subjected to the same amount of pressure on the square inch; neither has it been tested at the same elevation as some other 10-inch guns, which, in proportion to their size have stood a more severe test. It is a fact, which may be clearly demonstrated, that if a 10-inch gun of 95 cwt. be fired at an elevation of 40° with 17 lbs. of gunpowder, then a gun of more than six times that weight would not be overloaded if its due proportion of powder were about 100 lbs. Has this gun been fired with one half of this? Until it has been satisfactorily proved to this extent, we feel sure that the authorities are justified in not considering Mr. Horsfall’s a successful achievement.

Whatever may be Mr. Horsfall’s impression with regard to the advantages of wrought iron for making cannon, I am satisfied, after a long and careful study of the results of all its varieties, from the most ordinary to the most perfect combination that has been manufactured—either for tenacity, tenuity, or resistance of lateral pressures—that it cannot answer in large guns.

This I think any one will admit, after considering the two following facts; which apply equally to all varieties and mixtures of wrought iron.

1. The strength of iron is at its maximum in the smallest mechanical structures.

2. The quality of the metal is improved as it is subjected to greater pressure and condensation.

The extent to which this improvement may be carried has never yet been ascertained; every fresh manipulation improves its quality. The tenacity of wrought iron is best displayed in a wire, drawn out until it is not thicker than a human hair. Large masses of wrought iron are weak and spongy in geometrical progression with the mass, and the crystalline or molecular form increases with the mass. If large forgings are carefully examined, crystals will be found whose facets would produce inches of surface; as was clearly demonstrated by the bursting of a 10-inch gun at Woolwich: made, if we mistake not, by Mr. Nasmyth.

Another very important cause which renders large masses of wrought iron unsound (and which was fatal in Mr. Nasmyth’s gun) is the impossibility of condensing tons of wrought iron equally all through the mass. No one has yet been able to overcome this difficulty.

When the force of a blow, however great, is exerted on the surface of a mass of metal, its effect is neutralized within a few inches of the surface; condensation takes place in inverse ratio from the point of impact, and thus the effect is limited. The force which produces this condensation tends also to elongate the fibres of the metal. This elongation is greatest in the immediate vicinity of the force; the fibres in the interior of the mass are less elongated therefore than on the exterior; and the fibres in the interior of the mass being less ductile (from the cause already explained) than those on the exterior, the interior of the mass elongates, by disintegration of its fibres or crystals, and a porous open mass is thus produced, surrounded by a fibrous case. Instances of this are to be seen in broken engine-shafts and anchors; and, indeed, in all large masses of wrought iron, whether fractured by design or accident.

Another cause of this defect in large masses of wrought iron, is the long continued heat to which it is necessary to expose such large forgings. The iron expands as it is heated, but it does not expand equally all through the mass; and the result of this is that the interior becomes porous and spongy: an appearance which must have been observed by every one who has operated upon large masses.

The shaft of the Leviathan weighs 26 tons; but, instead of resisting twenty-six times the pressure of a shaft one ton in weight, it will, from the causes already mentioned, be found unequal to half that amount.

We have watched with much interest the forging of these immense shafts; and the difficulties attending the forging of this structure prove the accuracy of our reasoning on the strength of large masses of wrought iron. The weight of the shaft when finished is 26 tons, and the waste during the process of welding amounts to 74 or 75 tons.

The present shaft is the third which has been manufactured; the two first having proved notorious failures: thus 200 tons of iron have been wasted; which we think is sufficient proof either of the unfitness of the material, or of imperfection in the method of construction. Moreover, I fear that when the vessel encounters a rolling sea, the sudden check and strain produced by the total immersion of one paddle-wheel and the freedom of the other, will subject the present shaft to a strain which will affect its duration; and a vessel costing nearly a million of money may thus be left to reach her port with crippled powers of propulsion.

Where, it may be asked, is the skill in devising engines more powerful than the ingenuity of man can beneficially work out? This has indeed been done in the case of the Leviathan; a monster vessel has been built, but all the engineering skill expended upon it has as yet been insufficient to bring it to perfection.

The skill hitherto displayed in welding large forgings of wrought iron into shafts, or other large masses, has been of a very low order; much more may be done than has yet been accomplished, if men will only set about it in a scientific manner. The present mode of proceeding is to build a structure of iron much as a builder would raise a structure of bricks; large and small pieces being mixed together until the requisite mass is obtained.

Now, a much simpler method, and one which we have tried on several occasions, is first to construct several segments of iron of the requisite length, and of dimensions equivalent to the intended object; each segment being fitted to fill its place amongst a given number of other segments (whether twenty, forty, or fifty segments be required,) so as to form a complete cylinder; as the wood-cut will fully explain:—