Constant improvement has been the watchword of the shipowner and the shipbuilder, and every decade has seen the ships of its predecessor become obsolete. The mixed paddle and screw leviathan, the "Great Eastern", built in the late 1850s, was so obviously before her time by some fifty years, and was so under-powered for her size, that she may be left out of our reckoning. Thus, to speak roughly, the 1850s saw the iron screw replacing the wooden paddle steamer; the later 1860s brought the compound engine, which effected so great an economy in fuel that the steamship, previously the conveyance of mails and passengers, began to compete with the sailing vessel in the carriage of cargo for long voyages; the 1870s brought better accommodation for the passenger, with the midship saloon, improved state-rooms, and covered access to smoke-rooms and ladies cabins.