Railways commonly used salt water load banks in the 1950s to test the output power of diesel-electric locomotives. They were subsequently replaced by specially designed resistive load banks. Some early three-phase AC electric locomotives also used liquid rheostats for starting up the motors and balancing load between multiple locomotives.
Liquid rheostats were sometimes used in large (thousands of kilowatts/horsepower) wound rotor motor drives, to control the rotor circuit resistance and so the speed of the motor. Electrode position could be adjusted with a  small electrically operated winch or a pneumatic cylinder. A cooling pump and heat exchanger were provided to allow slip energy to be dissipated into process water or other water system.
Massive rheostats were once used for dimming theatrical lighting, but solid-state components have taken their place in most high-wattage applications.