<P> Corliss used separate ports for steam supply and exhaust, which prevented the exhaust from cooling the passage used by the hot steam . Corliss also used partially rotating valves that provided quick action, helping to reduce pressure losses . The valves themselves were also a source of reduced friction, especially compared to the slide valve, which typically used 10% of an engine's power . </P> <P> Corliss used automatic variable cut off . The valve gear controlled engine speed by using the governor to vary the timing of the cut off . This was partly responsible for the efficiency improvement in addition to the better speed control . </P> <P> The Porter - Allen engine, introduced in 1862, used an advanced valve gear mechanism developed for Porter by Allen, a mechanic of exceptional ability, and was at first generally known as the Allen engine . The high speed engine was a precision machine that was well balanced, achievements made possible by advancements in machine tools and manufacturing technology . </P> <P> The high speed engine ran at piston speeds from three to five times the speed of ordinary engines . It also had low speed variability . The high speed engine was widely used in sawmills to power circular saws . Later it was used for electrical generation . </P>

Who built the first really efficient steam engine that could be used for numerous tasks