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.”