The first ocean-going screw steam-ship of her class to which the modern double or twin-screw system was applied was the iron vessel _Far East_, which was launched from Dudgeon’s yard, Millwall, towards the close of 1863. She was intended for the China tea trade of the owners of the _Lightning_ and _Thunder_. The _Far East_ was 227 feet between perpendiculars and 210 feet on the keel; 34 feet beam, 22 feet moulded depth, and 20 feet 6 inches depth of hold; her depth at load water-line was 17 feet, her displacement 2200 tons, and her builder’s measurement tonnage 1258 tons. On her upper deck she had a capacious poop and forecastle, and there were deck-house and cabins amidships. Her engines were of 150 nominal horse-power, driving a two-bladed lifting screw under each quarter. The engines had annular combined cylinders, the diameter of the high-pressure cylinder being 24 inches and of the expansive cylinder 50 inches, with a piston stroke of 24 inches. The screws were 8 feet 2 inches in diameter, with a pitch of 16 feet. Each of the two boilers had six furnaces with 109 square feet of firebar surface, and a tube surface of 1883 feet. The shafting of the screws projected through a wrought-iron tube of great strength bolted to a false iron bulkhead clear of the ship’s frame. The tube at its outer end was connected with a wrought-iron slide, which guided the screw to the well when being lifted, or to the shafting when being lowered. The screws were raised by a worm and barrel apparatus. The lower and top masts were of iron bolted together through flanges, and the topgallant masts fitted closely into the topmast heads, so that the masts from deck to button looked like immense slender poles. There were no tops, but light iron cross-trees spread the rigging, and preventive top and topgallant backstays were carried far aft of the lower rigging. Her funnel was placed well abaft the main-mast. She was given a full rig on all three masts, and in addition carried fore and main try-sails. No sooner was she afloat than the double-screw steamer _Pallas_ was sent into the water from the adjoining slipway; this being the first time on record that two iron twin-screw vessels were launched from the same yard on the same day. In January 1865 the double twin-screw steam-ship, _Louisa Ann Fanny_, was launched, and as it was thought she might possibly be acquired by the Confederates, the bunkers were so arranged as to afford ample protection for her engines from hostile shot. Her machinery consisted of horizontal direct-acting engines with cylinders of 40 inches diameter, and 22¹⁄₂ inch stroke, driving two three-bladed screws of 9 feet 3 inches diameter and a pitch of 17 feet 3 inches, the distance from centre to centre of the screws being 10 feet 10 inches. She attained, when loaded, a speed estimated at 15³⁄₄ miles an hour after allowing for the tide.