Ship-building is an art whose origin is lost in antiquity. Perhaps the Chinese were the earliest practisers of it, and the ships of the Greeks, Romans, and Phoenicians must have been of a high order of merit. The barbarian inroads seem to have destroyed the art generally, though round the Mediterranean it still flourished, and the Norse and Saxon galleys had their good points. A Norse galley, lately discovered in a cairn, was fitted for sails and oars, and was 75 feet long by 16 feet wide. Though an English fleet existed, and fought in early times, England made but slow progress in later times. The order of excellence seems to have been Genoese, Spanish, French, English, and even in the 17th and 18th centuries England copied French models. The Grace de Dieu, built by Henry VIII. in 1514, was of 1,000 tons burder, contained 700 men, and carried 120 guns; but in the 16th century England, in spite of defective types, could hold her own with Spain and Holland. In 1637 appeared the Sovereign of the Seas, the first English three-decker; but in the beginning of the 19th century England, and still more America, took the lead. The Baltimore clippers were the first to demonstrate the advantage of sharp over rounded bows, and the square-rigged clippers of the Chinese tea-trade were a further revelation in this direction. The discovery of steam caused a great revolution, but England still clung to faulty theories, which America discarded in favour of practical advantage. The Sirius (1838) was the first steamer that went to America, and the first iron ship was the Great Britain, constructed in 1843. The last three-decker built for the navy was the Duke of Wellington. The Great Eastern gave an impulse to the building of large vessels. As types of two different styles, one may look at the graceful lines of the City of Rome and the straight, perpendicular bows of the Cunarders. The invention of the screw was one of the greatest improvements in the construction of ships, since it enabled large vessels to enter harbours which would have been impossible for broad paddle steamers. The wooden ship is become so obsolete that it is hardly worth while to describe the method of building it. The keel, which was so important in a wooden ship, of which it was the backbone, is not of so great importance in an iron ship, which is bolted together, and whose parts mutually support each other. The keel is formed of plates riveted together, and from these arise the ribs, which are held rigid by iron beams. fhe skin of plates is riveted on to these ribs by thousands of rivets, and sometimes there is an inner skin, which adds to the stability and safety of the vessel. The same object is advanced by the watertight compartments, longitudinal and transverse, which are now almost a constant feature of newly-built ships. When a ship is ready for launching, parallel timbers, called "ways," are arranged under the keel on each side, and upon these are loose timbers, well-greased, and reaching almost to the vessel, wedges of soft wood being driven in between these timbers and the ship's side; the whole apparatus is called a cradle. At the moment of the launch the wedges are knocked away, and all fastenings, except a cable and anchor which drags along the ground and checks the impetus of her enormous weight, are loosed, and she glides with the greased timbers down the ways into the water. There is not so much uniformity of type and design among modern ships of war as in merchant and passenger steamers, since authorities are at perpetual variance as to the merits of different designs.