The _Waterwitch_ is chiefly remarkable for the trial given in her to Mr. Ruthven’s system of hydraulic propulsion. A small boat was fitted with the machinery and tried on the Thames. A vessel provided with the Ruthven apparatus was built to the order of the Prussian Government in 1853, and for many years worked satisfactorily on the Oder. The chief engineer of Portsmouth Dockyard, when testifying to the Government as to the capabilities of the Ruthven method, said it afforded extraordinary facilities for manœuvring under steam, and he saw no reason why a speed should not be attained with it equal to that of the paddle or screw. A vessel called the _Seraing_ was built by the Belgian shipbuilding firm of Cockerill and fitted with a Ruthven propeller, and when tried against a paddle-wheel vessel of the same form, tonnage, and horse-power was found to have about 10 per cent. greater speed than the other. The testimony of the chief engineer of the Portsmouth Dockyard resulted in the _Waterwitch_ experiment. The hull of this vessel was constructed by the Thames Iron Works and Shipbuilding Company, and the design of the engines and the construction of the enormous turbine wheel, of which the propeller consists, were entrusted by the Admiralty to Messrs. Dudgeon. The _Waterwitch_ was built of iron and was of 778 tons measurement, 162 feet in length by 32 feet in breadth, and 13 feet 9 inches in depth. She was flat-bottomed, broad in proportion to her length, and double-ended and had a rudder at each end. Her armour consisted of a belt of plating 4¹⁄₂ inches in thickness at the water-line and centrally on her broadside, with armour-plated bulkheads across her upper deck, the object of the latter arrangement being to enable her to fight her guns over her deck in line with her keel, through gunports in the thwartship bulkheads as well as through broadside ports. For the machinery, and in the bottom of the vessel near the centre, was a long and shallow iron box with its length in the direction of the vessel. The lower side of this box had an immense number of small rectangular orifices, admitting water from outside and under the ship’s bottom, the passage of the water being controlled by valves which were only opened when the engines were at work. The turbine wheel drew the water in through the bottom of the vessel and ejected it through copper propulsion pipes and nozzles, through an aperture on each side of the ship, a little below the water-line.