Parsons' steam turbine with generator, 1891.

Parsons' steam turbo-generator, 1891. Until the invention of the steam turbine by Charles Parsons (1854-1931) in 1884, steam engines could not turn fast enough to produce electricity efficiently on a large scale. Used at the Cambridge Electric Light Station, this turbo-generator was the first to show that turbines could be run as economically as the best steam engines. Turning at 4,800 revolutions per minute, it had a power output of 100 kilowatts, and operated for thirty years. Steam turbines still drive most generators today.