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. 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.