Victoria and Alexandra form a twin-tandem compound engine. Together, they can deliver 3000 horsepower – enough to run twenty thousand 100W light bulbs! The low-pressure cylinders have piston slide valves. Condenser water is taken from the nearby river Beal. Photo courtesy of Jeff Mills The flywheel (centre, edge-on in the photograph) is 28 feet in diameter and weighs over 80 tons! To regulate the speed, a Whitehead governor controls steam input through Craig’s cut-off gear to Corliss valves in the high-pressure cylinders. From grooves in the flywheel surface, a rope race (44 ropes) transferred power to the mill machinery (via line-shafts on the five floors of the mill) and to a pair of alternators (to make electricity for lighting).