As ships were made larger, however, the nature of the stresses they had to bear became better understood, and precautions had to be taken to prevent the hogging and sagging to which they are subjected by the motion of the sea, besides the lateral and other stresses. In 1835-6 Mr. Russell built three small iron vessels, one of which had a longitudinal middle-line bulkhead and four transverse bulkheads connected by longitudinal stringers and without transverse frames. The other two had no longitudinal bulkheads but were fitted with a greater number of transverse partitions and stringers. He applied the latter method in 1850 to a small iron screw boat on the Humber, and in her some deep web plates were fastened by angle irons to the shell-plating and were also stiffened with angle irons along the inner edge. The inventor described this arrangement as being ordinary transverse bulkheads with the whole of the centre portion removed. The same year he built an iron paddle-steamer, 145 feet in length by 15 feet beam, and 7 feet 6 inches depth, on the longitudinal principle. Notwithstanding its extraordinary length in proportion to its beam and depth the vessel was a perfect success. One notable vessel constructed on this principle was the _Rhenus_, 197 feet over all, by 25 feet extreme breadth, and 9 feet depth, and drawing only 3 feet of water. These vessels, which were almost experimental in character, were followed by several others of a more highly developed type, such as the _Baron Osy_, a fine and fast paddle-steamer launched in 1855 for the London and Antwerp service. She was strengthened with the partial or open bulkheads of the type already described, which acted as frames, and had broad top stringers under the deck. This vessel had an oscillating condensing engine with two cylinders, and her paddles gave her a speed above that of other vessels on the route. The success achieved by her, both in regard to constructional strength and seaworthiness, had not a little to do with the designing of the _Great Eastern_. Before this, however, in 1852, Scott Russell designed with Brunel, who was consulting engineer to the Australian Royal Mail Steam Navigation Company, two steamers, the _Victoria_ and _Adelaide_, on the wave-line principle, but they were not on his longitudinal system though including some of its features. In these vessels he introduced for the first time fore and aft bulkheads amidships combined with a part iron deck. They had an important influence on the adoption of the longitudinal system, as the constructional strength of the vessels was provided for by the addition of a flat keelson extending almost to the bilges and connected at either side with a longitudinal bulkhead which formed the coal bunkers and rose as high as the main deck, the hull thereby being transformed into a powerful box-girder. The experience derived from these vessels caused them to be the forerunners