Rowing, sometimes referred to as crew in the United States, is a sport whose origins reach back to Ancient Egyptian times. It involves propelling a boat (racing shell) on water using oars. By pushing against the water with an oar, a force is generated to move the boat. The sport can be either recreational for enjoyment or fitness, or competitive, when athletes race against each other in boats. There are a number of different boat classes in which athletes compete, ranging from an individual shell (called a single scull) to an eight-person shell with a coxswain (called a coxed eight). Modern rowing as a competitive sport can be traced to the early 17th century when races (regattas) were held between professional watermen on the River Thames in London, United Kingdom. Often prizes were offered by the London Guilds and Livery Companies. Amateur competition began towards the end of the 18th century with the arrival of "boat clubs" at the British public schools of Eton College, Shrewsbury School, Durham School, and Westminster School. Similarly, clubs were formed at the University of Oxford, with a race held between Brasenose College and Jesus College in 1815. At the University of Cambridge the first recorded races were in 1827. Public rowing clubs were beginning at the same time; in England Leander Club was founded in 1818, in Germany Der Hamburger und Germania Ruder Club was founded in 1836 and in the United States Narragansett Boat Club was founded in 1838 and Detroit Boat Club was founded in 1839. In 1843, the first American college rowing club was formed at Yale University. The International Rowing Federation (French: Fédération Internationale des Sociétés d'Aviron, abbreviated FISA), responsible for international governance of rowing, was founded in 1892 to provide regulation at a time when the sport was gaining popularity. Across six continents, 150 countries now have rowing federations that participate in the sport. Rowing is one of the oldest Olympic sports. Though it was on the programme for the 1896 games, racing did not take place due to bad weather. Male rowers have competed since the 1900 Summer Olympics. Women's rowing was added to the Olympic programme in 1976. Today, there are fourteen boat classes which race at the Olympics. Each year the World Rowing Championships are staged by FISA with 22 boat classes that race. In Olympic years, only the non-Olympic boat classes are raced at the World Championships. The European Rowing Championships are held annually, along with three World Rowing Cups in which each event earns a number of points for a country towards the World Cup title. Since 2008, rowing has also been competed at the Paralympic Games. Major domestic competitions take place in dominant rowing nations and include The Boat Race and Henley Royal Regatta in the United Kingdom, the Australian Rowing Championships in Australia, the Harvard–Yale Regatta and Head of the Charles Regatta in the United States, and Royal Canadian Henley Regatta in Canada. Many other competitions often exist for racing between clubs, schools, and universities in each nation.