YACHT, a light and comparatively small vessel, propelled by means other than oars. The term is now limited to vessels used for pleasure, or for racing purposes. For sailing yachts see YACHTING. Since 1840 power yachts have been increasingly used, especially as long distance cruising became a favourite pastime of the rich. The earliest power yachts were paddle boats, but the paddle was in time abandoned entirely in favour of the screw. For many years steam auxiliaries were the fashion. As a rule they were built with such a small beam that some canvas was necessary for steadying purposes. Of these cruiser yachts perhaps the highest development was reached in the "Valhalla," a ship rigged auxiliary with triple expansion engines of 1,490 tons Thames Measure ment, built in 1892. The purely steam yacht developed steadily and during the last decade of the nineteenth century there was a boom in such construction, particularly for owners in the United States. Conspicuous among the big yachts built during this period were the "Valiant" of 1893, 2,184 tons, the "Lysis trata" of 1900, 2,082 tons, and the "Mayflower," 1,844 tons which was for a time the official yacht of the President of the United States.
The internal combustion engine was used for pleasure purposes at sea from the early days of the loth century, almost as soon as it became practical on land, but to begin with it was in small craft only. For some years before the war the size of yachts propelled
by petrol engines, either as full power or as an auxiliary, was increasing steadily and when war broke out the first Diesel engined yachts were under construction.
After the war the full-powered motor yacht of considerable tonnage, with either Diesel or semi-Diesel machinery, established itself in popular favour in the place of the steam yacht, very few of the latter type having been built of recent years.
The "Nourmahal" of 2,001 tons, the "Savarona" of 1,833, and the "Warrior" of 1,245 tons are typical of the big modern motor yachts, while engines have been installed for auxiliary purposes in yachts of every size, from the 1,195-ton "Flying Cloud" built for the Duke of Westminster to small cruisers of three and four tons. The new cruiser yacht without auxiliary power is, in fact, now the exception and it has even been found necessary to draw up rules forming racing classes of auxiliaries.