In the Sea of Azov, in the spring of 1855, Commander Cowper Coles, of H.M. steamer Stromboli, constructed in a single night, of barrels, spars and boards, a raft capable of bearing heavy artillery, which he named the Lady Nancy; by means of which he brought within range and destroyed by shell fire the Russian stores at Taganrog.
The naval operations of this war had drawn general attention to the special problems in connection with the navigation of shallow waters by vessels with a heavy armament, and Commander Coles’ exploit immediately excited official interest. Models of armed rafts were submitted by him for Admiralty inspection, and shortly afterwards he was himself ordered home to give advice upon the requirements of this form of construction: in connection with which the necessity for armour protection for the gun or guns was a point early insisted on by him. In that same year he sketched a design for a belted shallow-draught vessel for the attack of stationary forts which he equipped with guns of the heaviest pattern, each working in a fixed hemispherical shield. From the fixed shield to a revolving turret was a small step. In a short time Commander Coles made himself the enthusiastic exponent of armour-protected guns, mounted in cupolas or turrets on or near the centre-line of a ship so as to give a command over nearly the whole sweep of the horizon. By such a system, he argued, a vessel could be endowed with a concentrated offensive power on any bearing unapproachable by broadside armament, however designed; all guns were effective on almost any bearing without diverting the ship, their force required no evolution to elicit, existing as it did when the ship was at anchor, in dry dock or on a constant course. The height of the turrets gave them a plunging fire, an effect particularly useful now that ships’ sides were armoured and their decks alone remained penetrable.
His advocacy of the turret system, aided by the technical assistance of Mr. Brunel, made a deep impression on a large section of the public and gained the interest of the Prince Consort. He did not profess the technical knowledge of a shipbuilder or designer; but in his insistence on the advantages to be derived from the method of mounting guns on the centre-line he wielded arguments of great natural force, and enlisted in his favour the professional sympathies of eminent builders and naval men. In 1860 he produced before the newly founded Institution of Naval Architects a plan of a sea-going ship carrying nine turrets, seven on the centre-line and two off-set so as to allow ahead fire from three turrets. In the following year he wrote to the Admiralty undertaking to prove that a vessel could be built on his principle of armament 100 feet shorter than the Warrior and in all military respects her superior: “I will guarantee to disable and capture her in an hour; she shall draw four foot less water, require only half the crew, and cost the country for building at least £100,000 less. I am ready to stand or fall on these assertions.”
Such a pronouncement could not be lightly passed over. Moreover, coast-defence vessels embodying the turret system—light-draught vessels characterized by small tonnage, small cost and indifferent sea-going qualities, in combination with massive protection and a large offensive armament—were already being built by the private firms of this country for various foreign powers. In ’61, for instance, Denmark had ordered the Rolf Krake, a turret gunboat carrying a 4½-inch belt and four 68-pounder guns, a pair in each of two armoured turrets; which three years later proved her value in action against a nominally superior force. Prussia had ordered her first ironclad, a turret ship. Holland, Italy, Brazil, Russia—all were known to be purchasing coast-defence vessels of the turret type. And two sea-going turret ships which had been ordered by the American Confederates, and which were building in this country—the Wyvern and Scorpion—had been seized and purchased by our government.
In these circumstances the Admiralty, though there was a preponderance of official opinion against the idea, resolved to countenance the turret system and give it a trial. The Royal Sovereign was cut down from a three-decker of 120 guns, armoured with a 5½-inch belt and a 1-inch deck, and equipped with four turrets carrying a total of five 12½-ton guns—two in the foremost and one in the remaining turrets. At the same time the Prince Albert, also a four-turret ship, was laid down by the firm of Samuda to an Admiralty order. These ships were a distinct success so far as the armament was concerned. They were certainly not ocean-going ships. There were many faults and undesirable features to be found in them. But the disposition of the armament was found satisfactory, and the captain of the Royal Sovereign reported most favourably of his ship, describing her as the most formidable man-of-war; “her handiness, speed, weight of broadside, and the small target she offers, increase tenfold her powers of assault and retreat.”
Time, and the progress of artillery, were on the side of Captain Cowper Coles. He saw, and the Admiralty advisers felt, that although it was possible to work existing guns on the broadside, yet increase in the size and weight of guns would sooner or later necessitate the mounting of them on accurately balanced turntables secured by central pivots on the centre-line. Only by such a method could the largest gun be worked and the full weight of metal be poured, as required, on either broadside. In fact the turret, the original object of which was purely defensive, was now regarded from a quite different point of view: as a convenient device by which guns of the highest calibre could be carried and worked. Was complicated machinery objected to? The common winch, the rack and pinion, were in constant use on every railway turntable, nor had the American turrets ever failed in action or caused a loss of confidence in their reliability. Reliance upon a central pivot was disliked? Yet the pivot was already in use for holding the broadside guns of our ironclads—a mere bolt 4 inches in diameter and itself exposed to gunfire.[169]
The Admiralty constructors were insistent on the practical difficulties which lay in the way of designing a satisfactory sea-going turret ship. The advantages which had been claimed for turrets were obvious, said Sir Edward Reed; the larger and heavier the individual gun, the greater the gain of mounting it in a turret. But enthusiastic advocates of this method lost sight of the fact that turrets were incompatible with masts and sails, and with the forecastle and high freeboard necessary for good sea-going qualities. At that time, 1865, it was possible to protect and work eight of the largest guns, mounted on the broadside, with as little expenditure of weight as would be required to mount four of the guns two in a turret on the centre-line; while in the latter case they could only fire in two different directions at the same time, whereas in the former they could fire in eight.
In order to allow both sides in the controversy to come to grips with the practical difficulties, a committee was formed at the Admiralty in May, ’65, and Captain Coles was asked to produce a turret-ship design by the aid of a draughtsman and with the drawings of the Pallas for guidance. His design, a vessel showing two 600-pounders each mounted in a centre-line cupola, was not considered suitable. So the Board resolved to build a ship to Sir Edward Reed’s design—a fully rigged and masted, high-freeboard ship, with an armour belt and protected bow and stern batteries, and with two centre-line turrets amidships mounted over a central battery, each carrying two 25-ton 600-pounder guns. This was the Monarch. She was the first truly ocean-going turret ship, and her performances at sea in ’69 in company with central-battery ships like the Bellerophon and Hercules proved her to be a valuable and efficient unit; by this experiment it was demonstrated, said Mr. Brassey, “that it was practicable to design a thoroughly seaworthy turret ship, although for sea-going purposes a central battery presents great advantages over the turret system.”
In the meantime Captain Coles had protested vigorously against the design of the Monarch as representative of his system. The plan was not his; the turrets were mounted so high that there was a large area to protect and the ship, unlike the low-freeboard ships of his own design, presented a large target. But his chief objection was, that the presence of a forecastle and an armoured bow battery annihilated the whole advantage of turret guns by preventing ahead fire from them. After protracted negotiations he obtained Admiralty permission to have a ship built to satisfy his own views and independently of criticism from Admiralty officials. In ’69 the Captain, built by Messrs. Laird to his drawings, was launched at Birkenhead. The Captain, although generally similar to the Monarch (the growth of artillery limited the number of the turrets to two), differed from her in one important respect: her designed freeboard was only 8 feet as compared with 14; and, by some error in calculation, this dimension proved to be only 6 feet when the vessel was in sea-going trim. This low freeboard, in conjunction with her large sail-area, produced a condition of instability at large angles of heel which led to disaster and sealed the doom of the fully rigged turret ship.
Even in the Captain ahead fire was not found possible. In the original plans she had the low freeboard favoured by her designer; but in the later plans poops and forecastles were added to give the necessary sea-going qualities, and ahead fire was thereby sacrificed. Complete mastage was given her: iron masts in the form of tripods to avoid the use of shrouds and to give as clear an arc of fire as possible. The rigging was all stopped short at, and worked from, a narrow flying deck which was built above the turrets. This flying deck provided a working space for the crew, who in a moderately rough sea would not be able to make use of the low upper deck.