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The details of both systems were subsequently more or less changed, and in January, 1863, a special mixed committee was appointed to make full experiments, and to investigate, with two calibres, viz.: 12 pounders and 70 pounders, the comparative merits in construction, en durance, range and accuracy, and in fact, in all the qualities which a gun should possess. The investigation was completed in April, 1865: the information collected showed, in both systems, results as to struc tural strength, and efficacy and accuracy of fire, which had not been previously attained; and while it was not in all respects conclusive as to the comparative merits of the guns, it pointed out more prominently than ever the perfection to which artillery might be brought by the application of engineering skill. In 1859, Sir William Armstrong was appointed Superintendent of the Royal Gun Factories, and, assisted by Mr. Anderson, established the new workshops for the construction of compound guns, which were fitted up with machinery of great power and accuracy, specially de signed for dealing with large masses of metal, r.nd for ensuring pre cision of manufacture in putting together the various parts of the Arm strong gun, which practically became the gun of the service. In 1863, Sir William Armstrong resigned his office, which has since been filled by Colonel Campbell, R.A., with Mr. R. Fraser, M. Inst. C.E., as his executive assistant. Irrespective of breech-loading, which has been abandoned in this country for heavy guns, and of rifling, in which the original mode has been to a great extent superseded by larger grooves to guide soft metal studs fixed on a hard metal projectile, the gun now generally manu factured for the service has undergone considerable structural changes, the most material one being the diminution of the number of parts, and the substitution of outer coils of fibrous Staffordshire iron for coils of the best Yorkshire iron, tough steel being still maintained for the lining, as best resisting surface wear. In the former type of gun, there was a forged breech-piece over the breech end of the steel lining tube, and, according to the size of the gun, a greater or less number of coiled tubes, carefully and successively fitted on. The pattern at pre sent in use for all guns consist of only four pieces :—viz., 1st, tire steel barrel or lining, 2nd, a coiled tube over the barrel, extending from the muzzle nearly to the trunnions; 3rd, the breech coil, consisting of three coils in alternate, directions, welded together, with a trunnion piece welded on, the whole piece shrunk on over the breech of the bar rel, and lapping over the front coil; 4th, the cascable. It is considered by the present authorities that the diminution in number of parts leaves the gun less liable to injury by accident endless dependant upon perfection in manufacture, and that practically an equal amount of strength is obtained; while it is held that a fibrous iron is to be pre ferred as more workable for coils, and as giving out its greatest strain over a greater distance than the best Yorkshire iron, which while stronger statically, is considered not to yield so far before fracture. It is stated that this change has diminished the cost of production by 35 or 40 per cent. The heaviest projectile thrown by any gun in the service prior to 1854, was the 200 lb. shell of the 13 inch mortar. The largest Armstrong gun hitherto constructed is an experimental one, which has a calibre of 13'1 inches, w-eighs 23 tons, and throws a shell of 600 lbs. It is intended that future 12 inch guns shall have a weight of 25 tons. The 11 inch gun lately constructed weighs 23 tons, and the weight of the several parts are as follows :—The steel barrel, 5 tons 5 cwt. in the rough, 2 tons 16 cwt. finished; the muzzle coil, 2 tons 15 cwt. in the rough, I ton 16 cwt. finished; the trunnion and breech coil, 22 tons 6 cwt. in the rough, 17 tons 17 cwt. finished; the cascable 14 cwt. in the rough, 11 cwt. finished. Two guns of Mr. Whitworth’s, of 9 inch calibre, and weighing 15 tons, are about to be delivered for trial. Prior to the mechanical improvements which have led up to the pre sent rifled guns, the greatest distance to which a projectile was ever thrown from a smooth bore gun was not much over 6,000 yards, and the limit of bombarding rauge at high elevations, with the 13-inch mortar, was 4,500 yards. With the modern ordnance projectiles have been thrown, with greater precision, to a range exceeding 10,000 yards ; the guns of the service make good practice at 6,600 yards; in fact, much better practice than was formerly attainable at 3,000 yards. At 1,000 yards the mean error of range of round shot from smooth bores may be taken as 43 yards, and that of rifled shot 19 yards; the mean error of direction (referred to the mean direction of all the shot), with round shot may be taken as 4'1 yards, and with rifled shot as 0'8 yard. At 2,000 yards the mean error of range of round shot may be taken as 60 yards, and that of rifled shot 21 yards; the mean error of direction with round shot 10 yards, and withtrifled shot 21 yards. In other words (the accuracy being inversely as the products of the errors), the rifled gun is, in one case more than eleven times, and in the other, more than thirteen times as accurate as the smooth bore. I have alluded to the structure and effects of British modem ordnance as giving another marked example of the advantage which has followed the application of engineering skill, and the production of machines of special power, accuracy,andfitness, with which thenamesofMr. Nasmyth, Mr. Whitworth, and Sir W. Armstrong are enduringly associated; and although I feel that a detailed comparison with the ordnance of other countries would perhaps be out of place, I may be allowed to express my belief that great as have been the advances made in the manufac ture of heavy ordnance in France, in Prussia and in the United States, neither have attained the certainty, the economy, or the perfection, of the productions of British factories. But all our improvements will be of little avail in time of need, until smooth bores are much more largely replaced by rifled guns. Meanwhile, for all practical purposes, we are almost unarmed in many of our so-called defences, at home and abroad. While such important changes have been effected in modern ordnance, the advance recently made in naval construction is alike remarkable, and would have been equally impossible without the resources of modem engineering. Without attempting to trace the progress from wooden to iron ships, or all the steps by which our naval architects have passed from the earliest to the most recent types of armour-clad ships, I propose toillus trate the general results by some comparisons between the structures of the “Warrior” and the “Hercules” as ships of 1860 and of the present period respectively. The “Warrior,” of 6,109tons, and 1,250 H.P., has armour-plating 4j inches thick, with teak backing of 18 inches, and an inner skin of 9-16ths of an inch, the whole being backed by vertical frames, 10 inches deep, and about 2 feet apart. A length of 213 feet in the middle part of the ship is plated, and upwards of 80 feet at each end unprotected. The armour-plating of the mid-ship battery extends from 6 feet 3 inches below the load line to the height of the upper deck, while the ends of the battery are protected by trans verse armour-plated bulkheads. The unprotected ends are divided into water-tight compartments, as a provision against the danger of shot holes near the water-line; but there is no protection to the rudder head and steering apparatus. The bow and stem guns on the upper deck are unprotected; and the only guns that can be fought under cover, are on the broadside, where they cannot be trained through an arc of more than 50 <> or 60°, a serious inconvenience with a vessel whose length of 380 feet is not favourable to rapid manoeuvring. The objections raised to a system which left so much of the ship unprotected, led, in ships of the “ Agincourt ” class, and the converted wooden line-of-battle ships, to the adoption of complete armour plating for the whole length of the ship, from the upper deck to a few feet below the water line; but as the increasing power of guns made it necessary that armour-plating, to be effectual, should have greater thickness and weight, it became evident that to continue complete pro tection would involve such increase in the size of a ship as to render her almost useless for manoeuvring. These considerations led to the introduction of the arrangement now adopted for the broadside ships of our navy, which provides a protected battery amidships, shut in by armour-plated bulkheads, and a belt of armour for the whole length in the neighbourhood of the water-line. By this means, in addition to the battery, protection is given to the neighbourhood of the whole water-line, to the engines and boilers, and to the rudder-head and steering apparatus. The first example of this distribution of armour was its application, in 1862, in the conversion of the “Enterprise,” a wooden sloop, from the designs of Mr. Reed, chief constructor of the Royal Navy. The ‘ Hercules,’ of 5,226 tons, and 1,200 HP., has armour-plating arranged on the same principle, with the important addition that besides the central battery on the main deck, 73 feet long, there are protected batteries on the main deck, at the bow and stern, 20 feet and 8 ft. long respectively. The lower edge of the armour is 6 ft. below the load line; on the batteries it extends up to the upper deck, and along the belt it ends at the main deck. The armour about the water-line is 9 inches thick, thence up to the port sill of the battery deck it is 8 inches, and the remainder 6 inches. The teak backing varies from 10 to 12 inches in thickness, and the skin plating is in two thicknesses of J-inch each. The vertical frames behind the armour 10 inches deep and 2 apart, with horizontal girders of about the same size, and at equal distances, placed outside the skin plating. Within this structure is a second wood backing, supported by a second series of skin plates and vertical frames, from the lower deck down to the lower edge of the armour. Before and abaft the central battery, there is iron plating below the planking of the main deck, as a protection from vertical fire where the armour only extends above the load-line. The sides of this shiparercccssed before and abaft the central bat tery, so that by means of embrasures in the armour-plated bulk-heads, the foremost and aftermost gun on each broadside can be traversed on turntables, so as to fire at an angle of 15° with the line of the keel, while that line is commanded by the guns in the bow and stern batteries. The “Hercules” is 8 inches wider in beam than the “ Warrior,” but 55 feet shorter, and of 833 tons less burthen. She will carry a smaller number of guns, but of much greater weight, so that in the particulars above given she has the elements of much greater power, both for offence and defence, while in the former quality she is perhaps inferior in some respects to a type of ship now on the stocks, such as the “ Invincible,” which has an upper-deck battery, to carry four guns, each of which can be fired either from the broadside or fore and aft, 7