Besides the competition between sail and steam, there was also going on for many years, as has already been suggested, the attempt to substitute iron for wood in the construction of vessels, and screw propellers for paddle-wheels as a means of propulsion by steam. In both branches of this transition, which were parallel but not necessarily connected, Great Britain took the lead, and she has rightfully reaped the benefit. How gradually the change came about will be seen from the following facts and figures: The first iron sailing ship was the _Vulcan_, built on the Clyde in 1818, and in the following year the first sailing vessel with an auxiliary engine crossed the Atlantic. This was the _Savannah_, a wooden ship of 350 tons, with portable paddles and an engine and boiler on deck. She was built at New York. The first vessel to cross the Atlantic using steam-power during the entire voyage was the _Royal William_, which was taken from Quebec to London in 1833; and in 1838 the first steamers of British build, the _Great Western_ and the _Sirius_, made the westward passage. The first steamer constructed of iron was the _Aaron Manby_, a small paddle-wheel vessel about 50 feet long, built at Horsley, England, in 1821; and the first screw steamer of any importance was the _Archimedes_, an iron vessel of 237 tons, built in England in 1839. The _Great Britain_, built at Bristol, England, in 1843, was the first screw, as well as the first iron steamer to cross the Atlantic, but it was not until 1850, when the Inman liner _City of Glasgow_ began to run regularly between Liverpool and Philadelphia, that iron screw steamers took a recognized place upon the ocean. It is to be noticed how closely these last dates correspond with those of the clipper ship era, which opened with the advent of the _Rainbow_ in 1843, and was brought to its greatest brilliancy through the discovery of gold in California and Australia in 1848 and 1851. At this time each nation was devoting its best talents to developing the material that lay nearest at hand; and while the American wooden-built type was earlier brought to perfection, its possibilities were more limited by natural causes. Greater economy, durability, and regularity of speed on the part of the iron screw steamer were the qualities that finally drove from the seas the far more picturesque and beautiful wooden sailing ship.