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us by their author from time to time, and we can only hope that the country and the world, when at length sensible of their obligations, may render the tardy meed of justice, if not of gratitude.

In his earliest communication, - a pamphlet published in the year 1845,- Mr. Treadwell seems to think that the appropriateness of the term “useful,” as applied to an improvement in implements of destruction, may be questioned. We need have no misgiving in this respect. So long as life and property, which the ravages of war destroy, are not the most valuable of human possessions, they may be justly yielded and taken, if need require, for the preservation of those that are. And 80 nations must always count among their greatest benefactors those whose inventions increase their strength and defence in war. And certainly those men who, by their inventive genius, revolutionize the art of war, exert a most powerful and enduring influence upon the fate of empires, the course of history, and the progress of civilization.

We in our day, within the last fifteen years, have witnessed a change in the means of attack and defence greater than any made in the two hundred years previous, - a change involving a complete revolution in tactics, both on land and on sea. To take a single illustration from heavy ordnance, in which the importance of the change impresses us when we are told that our strongest forts, armed with the best guns we had ten years ago, could oppose no effectual resistance to the entrance of such ships as are now built into any of our harbors; and that a ship could now be built and armed, which, singly, would overmatch our whole navy as it was in 1855.

Fortunately, the balance is redressed by equal improvements in defence.

The improvement in fire-arms, both great and small, is in their increased range and precision. When the effective range of a musketbullet was extended from two hundred yards to fourteen hundred or more, it became imperatively necessary that ordnance should be improved in the same ratio, or it would be useless, as gunners and horses would be picked off by small arms long before they could effectively reach the enemy. This improvement in guns of great calibre has been made, with consequences the importance of which, present and prospective, cannot be over-estimated.

But the point which we have to consider is, thất this increased range and precision are entirely dependent on the augmented strength of the gun. The weakness of the gun is the only thing that imposes a limit to the range short of the absolute strength of the explosive material used. It is the strength of the gun which not only gives the range, but makes rifling possible, with precision and all the advantages of the elongated shot. All inventions relating to the different modes of rifling, the form of the projectile, and the devices for breech-loading, are necessarily subordinate to the question of strength ; with this sufficient, those become simple problems, to be rapidly determined by the ingenuity of many inventors.

Now the limit of strength of cast-iron and of bronze cannon had long ago been reached. Excepting Captain Rodman's improvement, and · certain modern advantages in working and casting metals, no material advantages had been gained over guns cast in the reign of Queen Elizabeth.

But the most effective guns of the present day embody new principles of strength. They are all built-up guns. With them are associated the names of Armstrong, Blakely, Whitworth, Parrott, and others. Whatever may be the relative merits of these several varieties, our interest is confined to the question of their strength, that is, to the principles of construction which have made them stronger than common guns, and rendered their respective subordinate improvements possible. These principles are two, and their introduction at different times into the manufacture of cannon constitutes two successive steps, and the only steps, which give distinctive character to the guns under consideration. Both originated with Mr. Treadwell.

These two inventions are often confounded, although more than ten years elapsed between them. The confusion is doubtless owing in some degree to the fact that the two are found combined in nearly all the modern built-up guns. The first initiated a system of construction which may be designated as the coil system; the second, what may be named the hoop system.

The first was successfully applied to the making of cannon by Mr. Treadwell in the year 1842, and a full account of it was published in 1845; the gist of the invention being in so constructing the gun that the fibres of the material shall be directed around the axis of the calibre.

This method of construction is described in Professor Treadwell's own language as follows: "Between the years 1841 and 1845 I made upwards of twenty cannon of this material [wrought iron]. They were all made up of rings, or short hollow cylinders, welded together

endwise ; each ring was made of bars wound upon an arbor spirally, like winding a ribbon upon a block, and, being welded and shaped in dies, were joined endwise when in the furnace at a welding heat, and afterwards pressed together in a mould by a hydrostatic press of one thousand tons' force.

“ Finding in the early stage of the manufacture that the softness of the wrought iron was a serious defect, I formed those made afterwards with a lining of steel, the wrought-iron bars being wound upon a previously formed steel ring. Eight of these guns were six-pounders of the common United States bronze pattern, and eleven were thirty-twopounders, of about eighty inches' length of bore and nineteen hundred pounds' weight.”

The soundness and value of this principle of construction were fully confirmed in England by the experiments of Sir William Armstrong in 1855, and attested by his evidence before a committee of the House of Commons in 1863. He there describes his own gun as one "with a steel tube surrounded with coiled cylinders,” — as “ peculiar in being mainly composed of tubes, or pipes, or cylinders, formed by coiling spirally long bars of iron into tubes and welding them on the edges, as is done in gun-barrels." His indirect testimony to the originality of Mr. Treadwell's process is equally clear, being that, within his knowledge, no cannon had ever been made upon this principle until he made his own in 1855, - he being, as we must suppose, ignorant of what · Mr. Treadwell had done thirteen years before. The statement of Mr.

Anderson (witness before the Commons' Select Committee), made before the Institute of Civil Engineers in 1860, is equally explicit as to the nature and value of this method of constructing cannon. And, finally, the high estimate of its importance abroad is shown not only by the honors and emoluments conferred by the British government on the re-inventor, but still more by the actual adoption of this gun as the most efficient arm yet produced. For it must be borne in mind that the faults or failures, complete or partial, of the Armstrong and similar guns are not of the cannon itself, as originally constructed, but of breech-loading contrivances, of the lead coating of the projectile, or of other subsidiary matters.

That our colleague's original invention, the value of which is now so clearly established, should have been so generally unacknowledged by inventors abroad is his misfortune, not his fault. For, not only were his guns made and tested here, and their strength as clearly demonstrated before 1845 as they have been since, not only was a full account of the process and of the results published here in that year, but a French translation of his pamphlet was published in Paris, in 1848, by a professor in the school of artillery at Vincennes ; and Mr. Treadwell's patent, with full specifications, was published in England before Sir William Armstrong began his experiments.

The difficulties to be overcome in making such a gun, — great at all times, as Sir William Armstrong and Mr. Anderson testify, — were far greater in 1842 than in 1863. These difficulties were mainly, if not wholly, in welding large masses of wrought iron in the shape of tubes or cylinders. It is for overcoming these difficulties that this medal is bestowed, and especially for the means and appliances by which this difficult mechanical achievement was effected in the furnace " by the agency of fire."

An incidental but noteworthy part of the improvement was the welding by hydrostatic pressure, - an operation which is just now coming into use in England, but has not yet attracted attention in this country.

We come now to the second improvement in the construction of artillery, — the invention of the hooped gun.

This is not always clearly distinguished, even by those occupied with the subject, from the gun formed of coiled rings. But a simple statement will bring into view distinctly the new principle of strength here introduced.

If an elastic hollow cylinder be subjected to internal fluid pressure, the successive cylindrical layers of the material composing it, counting from within outwards, will be unequally distended, and the resisting efficiency of the outer layer will be less than that of any layer nearer the axis. And if the walls of the cylinder are thick, and the internal pressure surpasses the tensile strength of the material, its inner layer will break before the outer one has been notably strained. Hence the tensile strength of a square inch bar of the material is the measure of the maximum pressure the cylinder can bear, when constructed as guns were before the introduction of the improvement now under consideration. The improvement does away with this limit, and enables us to go indefinitely beyond it."

This is accomplished by so constructing the gun that the inner layers are compressed by the outer ; whereby the internal pressure is first resisted by the outer layers, which must be distended enough to allow

the internal compressed portion to attain its normal condition before this internal portion (which is the first to break in the common gun) is subject to any strain at all. It will be perceived that if this principle could be rigorously applied, a cannon could be made so perfect that, when subjected to a bursting pressure, every fibre, from the internal to the external surface would be at that instant equally extended, each contributing its full share of resistance to fracture. The whole resistance would be proportional to the area of fracture.'

This was supposed to be the case in common cylinders, before the error was pointed out by Barlow, and also by Lamie and Clapeyron. And it was this erroneous supposition that led Count Rumford to his exaggerated estimate of the force of gunpowder, as tested by its power of bursting gun-barrels. If he had used the theory which gave origin to the hooped gun, his results would nearly have agreed with modern observations.

The demonstration of the superiority of the hooped gun, with detailed directions for its construction, is contained in a paper read before this Academy in February, 1856, and published at the beginning of the sixth volume of our Memoirs. This was the first published account of the invention, which had been patented nearly a year before. Captain Blakely's pamphlet, published in England in 1858, sets forth the advantages of this construction by similar arguments; as also does an elaborate paper read by Mr. Longridge before the Institution of Civil Engineers in February, 1860. Both these gentlemen, however, were engaged in researches upon this subject at an earlier date, but not so early, it would appear, as was Mr. Treadwell.

The validity of the principle, and the soundness of Mr. Treadwell's views upon the whole subject, as set forth in his memoir, have been amply confirmed by special experiments made in England with the Blakely and Whitworth guns, and by experience in this country during the last four years with the Parrott and the Blakely guns.

It must not be supposed that the earlier invention is superseded by the later one. That is used in forming the hoops of the Parrott gun, and in most of the British guns. And the best gun which could now be made, as experience has shown, would be composed of a barrel of cast-iron or steel, enclosed and compressed by a cylinder of coil.

We need not discuss the question of priority of invention between Mr. Treadwell and others, competitors for a share in the honor of producing the modern cannon. His independence of each and all of them


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