In ’63 Sir Edward Reed, at that time Mr. Reed, one of the graduates of the school which in ’48 had been established at Portsmouth Dockyard, was appointed to the office of Chief Constructor of the Navy. Possessed of broad and original views and gifted to an unusual degree in the arts of exposition and argument, he made himself responsible for designs of warships differing widely from their large and unwieldy precursors. The first of these was the Bellerophon, a short and easily manœuvred, fully rigged belt-and-battery ship, carrying ten 12-ton Armstrong guns for broadside fire in the battery, and two 6-ton guns for ahead fire in a small armoured battery in the bows. Not only in the disposition of her armament was the Bellerophon different from all former ships. She was a radical departure from existing practice in many important respects. Constructionally, she was built on a new “bracket-frame” system designed to give great girder strength for small expenditure of weight, already in vogue for mercantile shipping. The use of watertight compartments was extended as a defence against an enemy ram, the system of double bottoms was extended as a consequence of the introduction of the torpedo. A powerful ram was carried, but the bow took a new form; a U- instead of a V-section was adopted in order to give buoyancy and thus minimize the tendency to plunge which was inherent in a fine-bowed ship; the section near the water-line being fined away so as to form a cut-water. Steel was largely used instead of iron, with a consequent saving of weight. A novel trim was given her—six feet by the stern—to give a deep immersion for the powerful screw and to assist the ship in turning quickly on her heel under the action of the balanced rudder; an adjustment which experience showed to have a detrimental effect on the propulsive efficiency.
Next came the Enterprise, a still smaller ship. In the Bellerophon, as we have seen, there was no bow fire possible from the central battery; in the Enterprise this was obtained by piercing the athwartship bulkheads of the battery with ports, and substituting movable for fixed bulwarks. The same arrangement was developed in the Pallas and Penelope, in which ships the arc of fire of the corner guns of the battery was further extended by the device of indented sides. Then came the Hercules, generally like the Bellerophon but with indented sides and, as a novelty, alternative ports in the battery armour by means of which the corner guns could be trained, on revolving platforms, to fire either on the beam or nearly in line with the keel; a system which presented an obvious disadvantage in requiring twelve ports for eight guns. In the Kaiser class, designed by Sir Edward Reed shortly afterwards for the German government, this disadvantage was obviated by the expedient of forming ports in facets of the battery set at forty-five degrees with the keel-line, and by muzzle-pivoting guns.
Both in the Bellerophon and the Hercules axial fire had only been obtained by the provision of special batteries, at the bow and stern, of partially protected guns. Now, this accumulation of weight at the extremities was a feature viewed with disfavour by naval opinion; moreover, these bow batteries did not meet the ever-growing demand for a considerable ahead fire. So in the Sultan, which carried a central-battery armament similar to that of the Hercules, an upper deck armoured battery was embodied, superposed on the after end of the main deck battery and carrying guns which gave both astern and beam fire; while, for bow fire, two 12-ton guns were mounted in the forecastle, but without any protection.
The central-battery system had now to sustain the greatest attack that had yet been made upon it by the advocates of centre-line turrets. The position of the central-battery school was already somewhat shaken; ordnance had grown to a weight and power which justified the main argument of the turret advocates; Lissa had just shown the importance of being able to concentrate on any one bearing a maximum of offensive power. Controversy raged hotly on the relative merits of turret and central battery.
In these circumstances the Admiralty in ’68 determined to consider both types, with a view to embodying the best arrangement in the new class of vessels then projected. The principal shipbuilders of the country were invited to compete, and were presented with specifications for a first-class warship so widely drawn as to leave them the greatest latitude in design. Of the seven designs submitted, three were of the central-battery type, three were turret ships, and one a compound of the two. After comparison with an Admiralty design produced by Sir Edward Reed, it was decided to adopt this in preference to those of the private firms, and to build a whole class of six ships to it. The result was the Audacious class—of which the best-remembered are the Iron Duke and the ill-fated Vanguard. In this class a strong all-round fire was obtained by arranging two central batteries of the same size, one on the main and one on the upper deck. The main deck battery had only broadside ports for its six 12-ton guns, each gun training thirty degrees before and abaft the beam; the upper deck battery had four guns of the same calibre mounted at ports cut in armour facets at forty-five degrees with the keel-line, and training through ninety degrees. To allow axial fire from these guns the upper battery was made to project slightly, sponson fashion, over the sides of the ship, and the bulwarks forward and aft of the battery were set slightly back toward the centre line to enable the guns to fire past them.
A final stage in the evolution of the central-battery ship was attained in the Alexandra, laid down in ’72. The type had proved tenacious of life, and, for masted vessels, still held its own up to this point against the turret system. The design for the Alexandra gave as complete an all-round fire as was attainable in a central-battery ironclad; for the first time, it was said, we really had a masted ship with satisfactory all-round fire. Generally like the Audacious class, the Alexandra possessed an advantage in that the two forward guns of the upper deck battery were 25 ton instead of 18 ton, and in having, in addition to the six broadside guns of the main deck battery, two additional 18-ton guns mounted so as to be capable of firing nearly ahead and on the beam as well. Designed to fulfil the requirements of “end-on” fighting, she made a heavy sacrifice of broadside fire to obtain a maximum of bow fire; and at a later date, when a different valuation had come to be placed on axial fire, this sacrifice was noted against her. “She could only take her place at a disadvantage in any form of battle which was suited to the armaments of the ironclads that had gone before her.”[167] Nevertheless she was a formidable vessel. Defensively, too, she was pronounced to be conspicuously successful; her armour belt, which attained a thickness of 12 inches at the water-line amidships, was carried down at the bow to cover and strengthen the stem, and to protect the vessel from a raking fire. For the protection of the stern against a raking fire, an armour bulkhead was worked across the after part, extending to a depth of 6 feet below the water-line.
The Alexandra was the last of the purely “central battery” ships.[168] By the time she was launched experience had set the seal of approval on another type, to the evolution of which we must now revert.
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It is difficult to trace to its source the invention of the armoured gun-turret. The inventive Ericsson is said to have envisaged at an early age the idea of a protected gun carried on a mobile raft, “an idea probably inspired by his river-rafts in Sweden”; and it is known that at a later date he planned in detail a primitive monitor, the design of which at the outbreak of the Crimean War he offered to Napoleon III. Perhaps the idea, which M. Paixhans first developed in public, of applying iron armour to a sea-going ship, induced the idea of a pivot-gun protected by an armour shield. A protected armament was found, as we have seen, in the French batteries built for the assault of Kinburn: the armoured vessel and the armoured gun were first embodied in the same unit; and though these units were the first to be tried in actual war, yet some years previously, in 1842 or thereabouts, a Mr. Stevens of New York had proposed and made an armoured floating battery. But in neither of these instances was the gun in a turret. The turret idea, like so many other inventions, had an independent development in Europe and in America. In each case war supplied the incentive. In America, in ’62, Ericsson himself produced in a national emergency the Monitor, the low, shallow-draft armoured vessel carrying two 11-inch Dahlgren guns in a steam-rotated turret which served to counter the Southern Merrimac, the rasée with the fixed penthouse armour roof over its guns which the Confederates had built by the light of French experience.
The Monitor, both in design and in the circumstances of its production, was a great achievement; its success gave sanction to the revolving turret as a form of structure by means of which a big gun could be carried and trained. Nevertheless it is doubtful whether it influenced to an appreciable degree the evolution of the sea-going turret ship on this side of the Atlantic. Already, when the Monitor fought her action with the Merrimac, the turret had been adopted in coast-defence ships ordered for European powers; and, dramatic though it was, the incident of Hampton Roads afforded merely a confirmation of the effectiveness of the turret form of gun mounting. It was to an episode of the Crimean War that the development of the sea-going turret ship was directly due.