Successful machine-gun designs came into existence in mid 19th century. Gatlings were the first widely used rapid-fire guns and, due to their multiple barrels, could offer more sustained fire than the first generation of air-cooled, recoil-operated machine guns. The first self-powered machine gun was invented in 1884 by Sir Hiram Maxim. The "Maxim gun" used the recoil power of the previously fired bullet to reload rather than being hand-powered, enabling a much higher rate of fire.