Pelton wheels are among the most efficient types of water turbines. It was invente by Lester Allan Pelton (1829-1908) in the 1870s, and is an impulse machine, meaning that it uses Newton's second law to extract energy from a jet of fluid. It should be noted that the original one piece cast impulse water turbine was invented by Samuel Knight in Sutter Creek, Ca in the California Mother Lode Gold Mining Region. Pelton modified this design to create his more efficient design. Knight Foundry is the last water powered foundry known to exist in the United States and is still operated using Knight impulse turbines. It is used for high heads and low discharge.